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Terrapene ornata ornata Agassiz, by John M. Legler
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Title: Natural History of the Ornate Box Turtle, Terrapene ornata ornata Agassiz
Author: John M. Legler
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Language: English
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UNIVERSITY OF KANSAS PUBLICATIONS
MUSEUM OF NATURAL HISTORY
Volume 11, No. 10, pp. 527-669, 16 pls., 29 figs.
March 7, 1960
Natural History of the Ornate Box Turtle,
Terrapene ornata ornata Agassiz
BY
JOHN M. LEGLER
UNIVERSITY OF KANSAS
LAWRENCE
1960
UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Robert W. Wilson
Volume 11, No. 10, pp. 527-669, 16 pls., 29 figs.
Published March 7, 1960
UNIVERSITY OF KANSAS
Lawrence, Kansas
PRINTED IN
THE STATE PRINTING PLANT
TOPEKA, KANSAS
1960
[Union Label]
28-773
Natural History of the Ornate Box Turtle,
Terrapene ornata ornata Agassiz
BY
JOHN M. LEGLER
CONTENTS
PAGE
Introduction 531
Acknowledgments 531
Systematic Relationships and Distribution 532
Fossils 534
Economic Importance 534
Study Areas 535
Materials and Methods 537
Terminology 539
Habitat and Limiting Factors 539
Habitat in Kansas 542
Reproduction 543
Mating 543
Insemination 545
Sexual Cycle of Males 545
Sexual Cycle of Females 549
Nesting 554
Eggs 558
Embryonic Development 560
Fertility and Prenatal Mortality 564
Reproductive Potential 565
Number of Reproductive Years 565
Growth and Development 565
Initiation of Growth 565
Size and Appearance at Hatching 566
Growth of Epidermal Laminae 568
Growth of Juveniles 575
Growth in Later Life 578
Annual Period of Growth 580
Environmental Factors Influencing Growth 580
Number of Growing Years 584
Longevity 585
Weight 586
Bony Shell 586
Color and Markings 593
Wear 595
Sexual Dimorphism 595
Temperature Relationships 598
Optimum Temperature 599
Basking 600
Toleration of Thermal Maxima and Minima 601
Hibernation 611
Diet 617
Populations 623
Movements 626
Locomotion 627
Daily Cycle of Activity 629
Seasonal Cycle of Activity 630
Home Range 632
Homing Behavior 636
Social Relationships 637
Injuries 638
Repair of Injuries to the Shell 641
Ectoparasites 643
Predators 646
Defence 648
Discussion of Adaptations 650
Summary 656
Literature cited 663
INTRODUCTION
The ornate box turtle, _Terrapene o. ornata_ Agassiz, was studied more
or less continuously from September, 1953, until July, 1957. Intensive
field studies were made of free-living, marked populations in two
small areas of Douglas County, Kansas, in the period 1954 to 1956.
Laboratory studies were made, whenever possible, of phenomena
difficult to observe in the field, or to clarify or substantiate field
observations. Certain phases of the work (for example, studies of
populations and movements) were based almost entirely on field
observation whereas other phases (for example, growth and gametogenic
cycles) were carried out almost entirely within the laboratory on
specimens obtained from eastern Kansas and other localities.
A taxonomic revision of the genus _Terrapene_ was begun in 1956 as an
outgrowth of the present study. The systematic status of _T. ornata_
and other species is here discussed only briefly.
Objectives of the study here reported on were: 1) to learn as much as
possible concerning the habits, adaptations, and life history of _T.
o. ornata_; 2) to compare the information thus acquired with
corresponding information on other emyid and testudinid chelonians,
and especially with that on other species and subspecies of
_Terrapene_; 3) to determine what factors limit the geographic
distribution of ornate box turtles; and, 4) to determine the role of
ornate box turtles in an ecological community.
Acknowledgments
The aid given by a number of persons has contributed substantially to
the present study. I am grateful to my wife, Avis J. Legler, who, more
than any single person, has unselfishly contributed her time to this
project; in addition to making all the histological preparations and
typing the entire manuscript, she has assisted and encouraged me in
every phase of the study. Dr. Henry S. Fitch has been most helpful in
offering counsel and encouragement. Thanks are due Professor E.
Raymond Hall for critically reading the manuscript.
Special thanks are due also to the following persons: Professor A. B.
Leonard for helpful suggestions dealing with photography and for
advice on several parts of the manuscript; Professor William C. Young
for the use of facilities at the Endocrine Laboratory, University of
Kansas; Professor Edward H. Taylor for permission to study specimens
in his care; Dr. Richard B. Loomis for identifying chigger mites and
offering helpful suggestions on the discussion of ectoparasites; Mr.
Irwin Ungar for identification of plants; and, Mr. William R.
Brecheisen for allowing me to examine his field notes and for
assistance with field work. Identifications of animal remains in
stomachs were made by Professor A. B. Leonard (mollusks, crustaceans),
Dr. George W. Byers (arthropods), and Dr. Sydney Anderson (mammals).
Miss Sophia Damm generously permitted the use of her property as a
study area and Mr. Walter W. Wulfkuhle made available two saddle
horses that greatly facilitated field work. The drawings (with the
exception of Fig. 21) are by Miss Lucy Jean Remple. All photographs
are by the author.
I am grateful also to the Kansas Academy of Science for three research
grants (totaling $175.00) that supported part of the work. The brief
discussion of taxonomic relationships and distribution results partly
from studies made by means of two research grants (totaling $150.00),
from the Graduate School, University of Kansas, for which I thank Dean
John H. Nelson.
Systematic Relationships and Distribution
Turtles of the genus _Terrapene_ belong to the Emyidae, a family
comprising chiefly aquatic and semiaquatic species. _Terrapene_,
nevertheless, is adapted for terrestrial existence and differs from
all other North American emyids in having a hinged and movable
plastron and a down-turned (although often notched) maxillary beak.
_Emydoidea blandingi_, the only other North American emyid with a
hinged plastron, lacks a down-turned beak. The adaptations of box
turtles to terrestrial existence (reduction of webbing between toes,
reduction in number of phalanges, reduction of zygomatic arch, and
heightening of shell) occur in far greater degree in true land
tortoises of the family Testudinidae. Four genera of emyid turtles in
the eastern hemisphere (_Cuora_, _Cyclemys_, _Emys_, and _Notochelys_)
possess terrestrial adaptations paralleling those of _Terrapene_ but
(with the possible exception of _Cuora_) the adaptations are less
pronounced than in _Terrapene_. A movable plastron has occurred
independently in two groups of emyids in the New World and in at least
three groups in the Old World.
The genus _Terrapene_, in my view, contains seven species, comprising
11 named kinds. Of these species, five are poorly known and occur only
in Mexico. _Terrapene mexicana_ (northeastern Mexico) and _T.
yucatana_ (Yucatan peninsula) although closely related, differ from
each other in a number of characters. Similarly, _Terrapene klauberi_
(southern Sonora) and _T. nelsoni_ (Tepic, Nayarit--known from a
single adult male) are closely related but are considered distinct
because of their morphological differences and widely separated known
ranges. _Terrapene coahuila_, so far found only in the basin of Cuatro
Ciénegas in central Coahuila, is the most primitive _Terrapene_ known;
it differs from other box turtles in a number of morphological
characters and is the only member of the genus that is chiefly
aquatic.
Two species of _Terrapene_ occur in the United States. _Terrapene
carolina_, having four recognized subspecies, has a nearly continuous
distribution from southern Maine, southern Michigan, and southern
Wisconsin, southward to Florida and the Gulf coast and westward to
southeastern Kansas, eastern Oklahoma and eastern Texas, and
characteristically inhabits wooded areas.
_Terrapene ornata_ is a characteristic inhabitant of the western
prairies of the United States, and ranges from western and southern
Illinois, Missouri, Oklahoma, and all but the extreme eastern part of
Texas, westward to southeastern Wyoming, eastern Colorado, eastern and
southern New Mexico, and southern Arizona, and, from southern South
Dakota and southern Wisconsin, southward to northern Mexico (Fig. 1).
It is the only species of the genus that occurs in both Mexico and the
United States. The northeasternmost populations of _T. ornata_,
occurring in small areas of prairie in Indiana and Illinois, seem to
be isolated from the main range of the species. The ranges of _T.
ornata_ and _T. carolina_ overlap in the broad belt of prairie-forest
ecotone in the central United States. Interspecific matings under
laboratory conditions are not uncommon and several verbal reports of
such matings under natural conditions have reached me. Nevertheless,
after examining many specimens of both species and all alleged
"hybrids" recorded in the literature, I find no convincing evidence
that hybridization occurs under natural conditions.
_Terrapene ornata_ differs from _T. carolina_ in having a low,
flattened carapace lacking a middorsal keel (carapace highly arched
and distinctly keeled in _carolina_), and in having four claws on the
hind foot (three or four in _carolina_), the claw of the first toe of
males being widened, thickened, and turned in (first toe not thus
modified in _carolina_). _Terrapene ornata_ is here considered to be
the most specialized member of the genus by virtue of its reduced
phalangeal formula, lightened, relatively loosely articulated shell,
reduced plastron, and lightly built skull, which completely lacks
quadratojugal bones (Fig. 2); most of these specializations seem to be
associated with adaptation for terrestrial existence in open habitats.
[Illustration: FIG. 1. Geographic distribution of _Terrapene
ornata_. Solid symbols indicate the known range of _T. o.
ornata_ and hollow symbols the known range of _T. o. luteola_.
Half-circles show the approximate range of intergradation
between the two subspecies. Triangles indicate localities
recorded in literature; specimens were examined from all other
localities shown. Only peripheral localities are shown on the
map.]
Two subspecies of _T. ornata_ an recognized. _Terrapene o. luteola_,
Smith and Ramsey (1952), ranges from northern Sonora (Guaymas) and
southern Arizona (southern Pima County) eastward to southeastern New
Mexico and Trans-Pecos, Texas, where it intergrades with _T. o.
ornata_; the latter subspecies is not yet known from Mexico but almost
surely occurs in the northeastern part of that country. The subspecies
_luteola_ differs from _ornata_ in being slightly larger and in having
more pale radiations on the shell (11 to 14 radiations on the second
lateral lamina in _luteola_, five to eight in _ornata_). In
individuals of _luteola_ the markings of the shell become less
distinct with advancing age and eventually are lost; shells of most
old individuals are uniform straw color or pale greenish-brown; this
change in coloration does not occur in _T. o. ornata_.
[Illustration: FIG. 2. Dorsal and lateral views of skull of
_T. o. ornata_ (_a_ and _b_) (KU 1172, male, from 6 ml. S.
Garnett, Anderson Co., Kansas) and of _T. carolina_
(_c_ and _d_)(KU 39742, from northern Florida). Note the
relatively higher brain-case and the incomplete zygomatic
arch in _T. o. ornata_. All figures natural size.]
Fossils
Of the several species of fossil _Terrapene_ described (Hay,
1908b:359-367, Auffenberg, 1958), most are clearly allied to Recent
_T. carolina_. One species, _Terrapene longinsulae_ Hay,
(1908a:166-168, Pl. 26) from "... the Upper Miocene or Lower
Pliocene...." of Phillips County, Kansas, however, is closely related
to _T. ornata_ (if not identical). I have examined the type specimen
of _T. longinsulae_. Stock and Bode (1936:234, Pl. 8) reported _T.
ornata_ from sub-Recent deposits near Clovis, Curry County, New
Mexico.
Economic Importance
Ornate box turtles, referred to as "land terrapins" or "land
tortoises" over most of the range of the species, are regarded by most
persons whom I have queried as innocuous. These turtles occasionally
damage garden crops and have been known to eat the eggs of upland game
birds. _Terrapene ornata_ is seldom used for food. A. B. Leonard told
me the species was eaten occasionally by Arapaho Indians in Dewey
County, Oklahoma. Several specimens in the University of Kansas
Archeological Collections were found in Indian middens in Rice County,
Kansas, from a culture dated approximately 1500 to 1600 A. D. The
flesh of _T. ornata_ occasionally may be toxic if the turtle has eaten
toxic fungi as has been recorded for _T. carolina_ (Carr, 1952:147).
Study Areas
Preliminary studies and collections of specimens were made at a number
of localities in northeastern Kansas in 1953 and 1954. Two small areas
were finally selected for more intensive study. One of these areas,
the University of Kansas Natural History Reservation, five and
one-half miles north-northeast of Lawrence in the northeasternmost
section of Douglas County, Kansas, is a tract of 590 acres maintained
as a natural area for biological investigations. Slightly less than
two thirds (338 acres) of the Reservation is wooded; the remainder
consists of open areas having vegetation ranging from undisturbed
prairie grassland to weedy, partly brushy fields (Fitch, 1952).
Although ornate box turtles were not numerous at the Reservation, the
area was selected for study because: 1) there was a minimum of
interference there from man and none from domestic animals; 2) the
vegetation of the Reservation is typical of areas where _T. ornata_
and _T. carolina_ occur sympatrically (actually only one specimen of
_T. carolina_ has been seen at the Reservation); and, 3) availability
of biological and climatological data there greatly facilitated the
present study. Actual field work at the Reservation consisted of
studies of hibernation and long-term observations on movements of a
few box turtles.
A much larger number of individuals was intensively studied on a tract
of land, owned by Sophia Damm, situated 12 miles west and one and
one-half miles north of Lawrence in the northwestern quarter of
Douglas County, Kansas. The Damm Farm lies on the southern slope of a
prominence--extending northwestward from Lawrence to Topeka--that
separates the Kansas River Valley from the watershed of the Wakarusa
River to the south. The prominence has an elevation of approximately
1100 feet and is dissected on both sides by small valleys draining
into the two larger river valleys.
The Damm Farm (see Pl. 15) has a total area of approximately 220
acres. The crest of a hill extends diagonally from the middle of the
northern edge approximately two thirds of the distance to the
southwestern corner. Another hill is in the extreme northwestern
corner of the study area.
The northeastern 22 acres were wooded and had small patches of
overgrazed pasture. Trees in the wooded area were Black Walnut
(_Juglans nigra_), Elms (_Ulmus americana_, _U. rubra_), Cottonwood
(_Populus deltoides_), and Northern Prickly Ash (_Xanthoxylum
americanum_). The areas used as pasture had thick growths of Buckbush
(_Symphoricarpos orbiculatus_) mixed with short grasses (_Bromus
japonicus_, _Muhlenbergia Schreberi_, and _Poa pratensis_). Farm
buildings were situated in the wooded area at the end of an entry
road. The southeastern 74 acres were cultivated; corn, wheat, and milo
were grown here and fallow fields had a sparse growth of weeds.
Most of the western two thirds of the study area, comprising 124
acres, was open rolling prairie (hereafter referred to as "pasture")
upon which beef-cattle were grazed (Pl. 16, Fig. 1; Pl. 17, Fig. 1;
Pl. 18, Fig. 2). Rock fences (Pl. 17, Fig. 2) two to four feet high
bordered the northern edge, southern edge, and one half of western
edge of the pasture. A wagon track lead from a gate on the entry road,
along the crest of the hill, to a gate in the southern fence. Except
for the latter gate and for ocassional under-cut places in low areas,
there were no openings in the rock fences through which box turtles
could pass. A few trees--American Elm, Hackberry (_Celtis
occidentalis_), Red Mulberry (_Morus rubra_), Osage Orange (_Maclura
pomifera_), Black Cherry (_Prunus serotina_), Box-Elder (_Acer
Negundo_), and Dogwood (_Cornus Drummondi_)--were scattered along
fences at the borders of the pasture and in ravines. Larger trees in a
small wooded creek-bed at the southwestern edge of the pasture were
chiefly Cottonwood, American Elm, Red Mulberry, and Black Willow
(_Salix nigra_). The only trees growing on the pasture itself were a
few small Osage Orange, none of which bore fruit.
Paths were worn along fences by cattle and in several places near the
fence, usually beneath shade trees, there were large bare places where
cattle congregated. Vegetation near paths and bare places was weedy
and in some places there were tall stands of Smooth Sumac (_Rhus
glabra_).
Rich stands of prairie grasses occurred along the top of the hill in
the pasture; bluestems (_Andropogon gerardi_, _A. scoparius_) were the
dominant species and Switchgrass (_Panicum virgatum_) and Indian grass
(_Sorghastrum nutans_) were scattered throughout. A number of small
areas on top of the hill were moderately overgrazed, as indicated by
mixture of native grasses with an association of shorter plants
consisting chiefly of Ragweed (_Ambrosia artemisiifolia_ var.
_elatior_), Mugwort (_Artemisia ludoviciana_), Japanese Chess (_Bromus
japonicus_), and Asters (_Aster_ sp.).
The upper parts of the hillsides were overgrazed moderately to
heavily. Limestone rocks of various sizes were partly embedded in soil
or lay loose at the surface. Depressions beneath rocks provided
shelter for box turtles as well as for other small vertebrates. Native
grasses were sparse in this area and gave way to Sideoats Grama
(_Bouteloua curtipendula_), extensive patches of Smooth Sumac, and
scattered colonies of Buckbrush.
Tall grasses were dominant on the lower hillsides and small patches of
Slough grass (_Spartina pectinata_) grew in moist areas. Ravines
originated at small intermittent springs on the sides of the hill. The
banks of ravines were high and steep and more or less bare of
vegetation. High, dense stands of Slough grass grew at intermittent
springs and along the courses of ravines; sedges (_Carex_, sp.) grew
where small pools of water formed and created marshy conditions.
Prairie grasses along the tops of ravine embankments formed a narrow
overhanging canopy of vegetation that was accentuated in many places
where the sod was under-cut by erosion or by the activities of
burrowing animals (Pl. 18, Fig. 1). Box turtles frequently sought
shelter beneath this vegetational canopy or burrowed beneath the sod.
On the highest part of the pasture near the entry road several small
areas were nearly bare, presumably because of heavy overgrazing;
grasses (except for scattered clumps of _Bouteloua curtipendula_ and
_Setaria lutescens_) were absent and dominant vegetation consisted of
Buffalo-bur (_Solanum rostratum_), Blue Vervain (_Verbena hastata_),
Mullein (_Verbascum Thapsus_), Ragweed, Asters, and a few Prickly Pear
(_Opuntia humifusa_). Two small areas on the pasture completely lacked
vegetation; these may have been wallows or the sites of old
salt-licks.
Three shallow stock ponds, behind earthen dikes in ravines, were
present on the pasture. The pond near the farm buildings ("House
Pond") and that in the southwestern part of the pasture ("Far Pond")
were present when studies of box turtles were begun. The largest pond,
in a deep ravine in the northern part of the pasture, was constructed
in June, 1956, and became filled in approximately one month (Pls. 16
and 18). Pond embankments were chiefly bare of vegetation because of
trampling by cattle; in a few places at the edge of the water, or in
places too steep for cattle to walk, there were small patches of
weeds, sedges, and Slough Grass. The ponds contained some water at all
times of the year. The only vertebrates permanently inhabiting the
ponds in the course of my studies were Bullfrogs (_Rana catesbeiana_)
and Leopard frogs (_Rana pipiens_).
The three parts of the pasture in which studies were concentrated were
designated as separate subdivisions. The northwest corner area (28
acres) was triangular and bounded on two sides by rock fences and on
its third side by a deep ravine. The southern ravine area (17 acres)
constituted the part of the lower southern hillside drained by a
series of ravines. The house pond area (seven acres) surrounded "House
Pond." Habitat in these three subdivisions of the pasture was
especially favorable for box turtles.
Materials and Methods
Observations were made at the Damm Farm on 102 days in the two-year
period beginning in Autumn, 1954; observations were concentrated in
the period from May to October although some observations were made in
every month, January and February excepted. Field work was done
chiefly in daylight hours but a few trips were made to the study area
at night.
Routine handling of each turtle captured at the Damm Farm consisted
of: marking, weighing and measuring turtle; recording the exact place
of capture, body temperature and environmental temperature; and,
recording miscellaneous items such as the presence of ectoparasites,
injuries, distinctive markings, and in some instances, the approximate
age of the turtle.
Excursions on the Damm Farm were made on foot in 1954 and 1955, and,
in 1956, on horseback. By using a horse, more ground could be covered
per unit of time, a better view could be obtained of immediate
surroundings, and, cattle on the area, being accustomed to horses, did
not become agitated as they would when unmounted persons were nearby.
The entire study area could not be inspected thoroughly in a single
day. It was usually more profitable to find and mark turtles along
fences, in ravines, or in other open areas, and subsequently to follow
their movements away from these areas by means of trailing threads.
Turtles could be observed from a distance through binoculars.
Cultivated areas were regularly scanned with binoculars but turtles
were seldom seen there. Behavior was observed by sitting motionless on
rock fences or in a blind on top of a stepladder.
No box turtles were removed from the study area. Specimens obtained in
other areas were used for studies of growth, reproduction, and food
habits. Measurements, weights, and data concerning temperature and
ectoparasites were obtained from specimens collected elsewhere as well
as from individuals on study areas.
Turtles were obtained by hand-collecting and in unbaited traps; the
number captured in a single day ranged from 12 to none. Traps, like
those used by Packard (1956:9) for tree squirrels, were set in the
mouths of burrows and dens, or--with leads to channel animals into the
trap--along ravines and rock fences. Traps set in the open were
covered to prevent death of turtles from overheating in direct
sunlight. Live-trapping provided much valuable data, although quail,
rabbits, opossums, and box turtles were caught with about equal
frequency in the traps.
Turtles were marked by notching the marginal scutes of the carapace by
means of a hacksaw blade, following the code system described by Cagle
(1939). Notches, one eighth to one quarter of an inch deep and wide
could be cut more quickly than filed and were more evident than
drilled holes which often became plugged with soil and obscured.
Hatchlings and juveniles were notched with a sharp knife.
Movements of individual turtles were studied by means of a
turtle-trailing device--similar to the kind first described by Breder
(1927) and later modified by Stickel (1950:355-356)--a tin can, cut to
fit the shell of a turtle, with an axle that bore a spool of thread
(Pl. 27, Fig. 1). The device was taped to the turtle; the free end of
the thread was tied to a stationary object. Thread payed out from the
spool through a guide-loop and marked the course of the turtle as it
moved away from the starting point. Because of its great strength and
elasticity (as compared to cotton), nylon sewing thread was used in
trailers. Ordinarily, turtles were unable to break the thread if it
became snarled or was expended. Cattle frequently tangled the thread
and displaced it but did not often break it. Ordinary spools were cut
down on a lathe so they would hold 600 to 800 yards of thread.
Turtle-trailing provided an accurate record of where and how far a
turtle had traveled, and to a lesser extent, the sort of activity in
which the turtle had been engaged (evidence of feeding, forms, or
trial nest holes). Trailers seemed not to alter the normal activity of
turtles.
Prominent landmarks were rare or wanting in most places on the
pasture. Locations of captures (or reference points in the movements
of trailer-turtles) were determined by triangulation with a Brunton
compass, using trees along fences as known points of reference. Rough
maps were made in the field and used later, along with compass
readings and measurements, to make a more precise record of movements
and captures on a large map (scale, 100 feet to one inch) of the study
area. Mapped points of capture in grassy areas were accurate within
ten to twenty feet; points of capture in areas where landmarks were
nearby were nearly exact. Areas were measured with a planimeter;
distances traveled by individuals were measured with a cartometer.
Turtles were measured in the field to the nearest millimeter with
large wooden calipers (of the type used by shoe salesmen) and a clear
plastic ruler. Measurements in the laboratory, especially in studies
of growth, were made, to the nearest tenth of a millimeter with dial
calipers. Measurements made on each specimen examined in the field
were: length of carapace, width of carapace, length of plastron (sum
of lengths of forelobe and hind lobe), width of plastron (at hinge),
and height. All measurements were made in a straight line. A spring
scale of 500 gram capacity, used in the field, gave weights accurately
within three grams. A triple-beam balance was used in the laboratory.
Unless otherwise noted, measurements are expressed in millimeters and
weights are expressed in grams.
Body temperatures were taken by means of a quick-reading Schultheis
thermometer inserted into the distal portion of the large intestine
with the bulb directed ventrally to avoid puncturing the bladder. Body
temperature of turtles were altered little or not at all in the few
seconds the turtles were held and no attempt was made (except for
small juveniles) to insulate them from the warmth of my hands. Data
recorded with body temperature were: air temperature (in shade,
approximately one inch from turtle); ground temperature (or water
temperature); behavior of turtle; weather conditions; nature of
vegetation or other cover; and, time of day. Unless otherwise noted,
temperatures are expressed in degrees Centigrade.
A maximum-minimum thermometer was installed near the buildings at the
Damm Farm. Notes on general weather conditions were made on each visit
to the study area. Additional climatological data were obtained from
the U. S. Weather Stations in Topeka and Lawrence, from records at the
Reservation, and from official bulletins of the U. S. Weather Bureau.
Stomachs and gonads were removed and preserved by standard techniques
soon after specimens were killed. The dates given to gonads were, in
all instances, the dates when the specimens were killed. Eggs were
prepared for incubation in the manner described by Legler (1956).
Females laying or containing eggs used in studies of incubation were
preserved for further studies and comparison with young hatched from
the eggs. Histological preparations were fixed in ten per cent
formalin or Bouin's fluid, embedded in paraffin, and stained with
hematoxalin and eosin.
Terminology
Names used for the epidermal and bony parts of the shell follow the
classification proposed by Carr (1952:35-39). The terms "scute,"
"lamina," and "scale" are used here more or less interchangeably for
the epidermal parts as are the terms "plate," "bone," and "element"
for the bony parts of the shell.
The term "form" is used here in the same sense that Stickel (1950:358)
used it in her study of _T. carolina_--to indicate a depression or
cavity made by a turtle in vegetation or soil. Forms correspond
closely in shape and size to shape and size of the turtle. Forms of
_T. ornata_ differ from those of _T. carolina_ chiefly in being made
most often in soil, over which there is a minimum of vegetational
cover. The term "den" refers to natural cavities (or cavities of
unknown origin) beneath rocks, in rock fences, or in cut banks. The
term "burrow," unless otherwise noted, refers to burrows made by
animals other than box turtles.
HABITAT AND LIMITING FACTORS
The known range of _T. ornata_ includes the southern half of the
Grassland Biome, part of the Desert Biome, and that part of the
Temperate Deciduous Forest Biome known as the Prairie-Forest Ecotone.
The species is found in microhabitats that differ widely in food
supply, temperature, moisture, and kind of soil. In spite of its
relatively high degree of morphological specialization, _T. ornata_ is
remarkably versatile in regard to habitat requirements.
Ornate box turtles are relatively inconspicuous in natural
surroundings and collectors seldom seek out and obtain specimens under
completely natural conditions as may be done with certain other
reptiles and amphibians by turning rocks, tearing apart logs, or
setting traps. Most series of specimens are obtained by hunting after
rains on roads or other natural breaks in vegetational cover. Detailed
information on habitat preferences is lacking.
Low temperature seems to be an important factor limiting the
distribution of _T. ornata_ in the northern part of its range. Box
turtles, like nearly all other reptiles occurring at these latitudes,
spend the winter in underground hibernacula. The depth to which the
ground freezes in the coldest part of the winter is therefore a
critical factor. The ground freezes to an average depth of 30 inches
or less over most of the range of the species; only in the extreme
northern part of the range (southern South Dakota, southeastern
Wyoming) does the ground freeze to an average depth of as much as 35
inches. Average depth of freezing is, in fact, less than 15 inches
over more than one half the range of the species. The average number
of frost-free days per year ranges from 130 to 140 days in the
northern part of the range to more than 250 days in the southwestern
part of the range.
_Terrapene ornata_ occurs from near sea level to elevations of more
than 5000 feet. Both subspecies are found at both high and low
elevations but _luteola_ is more consistently taken at high elevations
than _ornata_. The latter subspecies commonly occurs at elevations
above 4000 feet on the high plains in extreme western Kansas and
eastern Colorado; the highest elevation from which I have examined
specimens of _T. o. ornata_ is between 4600 and 4700 feet near Akron,
Washington County, Colorado. The greater part of the known range of
_T. o. luteola_ lies above 3000 feet.
Norris and Zweifel (1950:1) observed _T. o. luteola_ on the Jornada
del Muerto, an elongate plain approximately 4500 feet high, in
southeastern Socorro County, New Mexico; box turtles were abundant on
the level part of the plain and on the bordering foothills but not at
higher elevations where the substratum was rocky. The authors
otherwise noted no preference for any kind of soil. The principal
elements of the plant associations in which the turtles were found
were creosote bush, yucca, mesquite, juniper, tarbush, and grasses.
Lewis (1950:3) reported that _T. ornata luteola_ inhabited the
yucca-grassland zone in Dona Ana County, New Mexico; he stated (_op.
cit._: 10) that individuals were commonly found on roads after rains
and in cloudy weather. No specimens were taken at altitudes higher
than 4300 feet.
I have examined specimens of _luteola_ from elevations of
approximately 5500 feet in Cochise County, Arizona, and Lincoln
County, New Mexico. These localities are probably at or near the
maximum elevation at which the species occurs. The texture of the
substrate is the most important factor limiting vertical distribution.
Ornate box turtles, like nearly all other turtles, excavate nests; _T.
ornata_ is a burrower, at least for purposes of hibernation.
Populations of the species, therefore, could not survive in areas of
hard unyielding substrata. Such substrata seem to be the most
important factor limiting altitudinal distribution.
Most of the area in which _T. ornata_ occurs is semiarid or arid.
Average precipitation in the warm season (April through September)
varies from approximately 25 inches in the northeast to less than ten
inches in the southwest. In drier parts of the range, precipitation is
unevenly distributed over the warm season. Long, hot, dry periods are
unfavorable for reptilian activity. _T. ornata_, like many other
reptiles inhabiting dry regions, survives long periods without water
by seeking shelter (usually underground) and remaining quiescent.
Populations of the subspecies _luteola_ live under far more rigorous
conditions in this respect than do the more northern populations.
Specimens of _luteola_ from Arizona that were kept for several years
in the laboratory under dry conditions and fed adequately, but at
infrequent intervals, were able to remain healthy and even to grow
whereas examples of _ornata_ kept under the same conditions soon
languished and died; _luteola_ seems to be physiologically adapted for
existence under arid conditions, where normal activity is sometimes
possible for only a few weeks in the year.
The prairies of Nebraska, Kansas, Oklahoma, and northern Texas seem to
provide the most nearly optimum habitat for the species; in these
regions box turtles are active on a large majority of the days from
April to October in years having average or better than average
precipitation and population density seems to be greater than in the
more arid parts of the range.
Activities of man have probably affected the density of populations of
the ornate box turtle in many parts of its range but appear not to
have acted as limiting factors except in certain areas along the
northern edge of the range (Blanchard, 1923:19-20, 24) where
disruption of grassland through intensive cultivation probably has
excluded the species. Unlike certain other reptiles of the Great
Plains (Fitch, 1955:64), _T. ornata_ seems not to have been
affected--either by direct decimation of populations or by disruption
of habitat--by intensive zoological collecting in restricted areas.
Environmental changes such as those resulting from overgrazing and
erosion, or from protection of the habitat from grazing could be
expected to cause long-term changes in populations of ornate box
turtles.
_Terrapene o. ornata_ is an omnivorous, opportunistic feeder,
primarily insectivorous but able to subsist on nearly any sort of
animal or vegetable food. The general food habits of _luteola_ are
poorly known but probably resemble those of _ornata_. Although kind of
food available probably does not limit the distribution of _T. ornata_
there are indications that it influences population density. In
Kansas, for example, dung insects are an important staple in the diet
and box turtles were found always to be more numerous in areas where
domestic cattle provided an abundant supply of dung than elsewhere. A
similar relationship probably existed in former times between box
turtles and native ungulates. Near extinction of buffalo in the Great
Plains possibly caused a decrease in populations of box turtles. Henry
S. Fitch told me that the number of _T. ornata_ at the Reservation
gradually declined after cattle were removed from the area in 1948.
In summary, the distribution of _T. ornata_ seems to be limited by: 1)
Presence of a substrate too hard to permit digging of nests and forms
(southwestern and western edges of range); 2) temperatures causing the
ground to freeze deep enough (approximately 30 inches) to kill turtles
in hibernacula (northern edge of range); and, 3) the lack of one or
more relatively wet periods in the course of the warm season,
preventing at least temporary emergence from quiescence (southwestern
edge of range).
HABITAT IN KANSAS
Clarke (1958:40-45) reported _T. o. ornata_ in all terrestrial
communities studied in Osage County; he considered the subspecies to
be characteristic of the "... cultivated-field community ..." and to
be of frequent occurrence in (but not characteristic of) the "...
Oak-Walnut Hillside Forest ..., Buckbrush-Sumac ..., and Prairie
communities ...". Brennan (1937:345) found _T. o. ornata_ to be
equally abundant in mixed prairie and prairie-streamside habitats in
Ellis County; the subspecies was much rarer on rocky hillsides and in
the habitat surrounding prairie ponds. Carpenter (1940:641) listed _T.
o. ornata_ as an inhabitant of "... tall and mixed-grass prairies ..."
(also in Oklahoma and Nebraska). Fitch (1958:99) found the order of
preference for habitats at the Natural History Reservation to be
grazed pasture land, woodland, open fields with undisturbed prairie
vegetation, and fallow fields with a rank growth of weeds.
At the Damm Farm the greatest number of box turtles was collected on
the pasture, especially in three areas designated in Plate 1 as the
"northwest corner," "southern ravine," and "house pond" areas. These
three areas had several features in common. All contained ravines and
rocky slopes that provided many places of concealment (dens, burrows
of larger animals, and suitable substrate for the excavation of
earthen forms). All contained water (in ponds and intermittent
streams) for most of the year; and, all were frequented daily by
cattle that left an abundant supply of dung in which box turtles
foraged. In addition, each of the three areas contained at least one
mulberry tree, under which fruit was abundant in the months of June
and July.
The relative numbers of box turtles found in different areas on the
Damm Farm were, of course, governed to some extent by my activity in
these areas and by the relative ease with which box turtles were seen
in different types of vegetational cover. Turtles were more easily
seen in the pasture (especially in sparsely vegetated or denuded
areas) where much of my field work was done on horseback, than in the
wooded areas, where excursions were usually made on foot. It was
evident, however, after mapping known ranges and studying patterns of
movement in marked turtles, that concentrations in the three
above-mentioned areas of pasture were an indication of actual
preference by turtles for the more favorable habitat in these areas
rather than the result of incomplete sampling.
REPRODUCTION
Mating
Mating takes place throughout the season of activity but is most
common in spring--soon after emergence from hibernation--and in
autumn. Turtles frequently copulated in the laboratory in spring and
autumn. Copulation was observed under natural conditions on several
occasions but only once at the Damm Farm.
Norris and Zwiefel (1950:4) saw two captive individuals of _T. o.
luteola_ copulating on 12 August; copulation lasted two hours.
Brumwell (1940:391-2) gave the following description of mating in _T.
o. ornata_. A male pursued a female for nearly half an hour, first
nudging the margins of her shell and later approaching her rapidly
from the rear and hurling himself on her back in an attempt to mount,
at the same time emitting a stream of liquid from each nostril. The
liquid was presumably water; both sexes had imbibed water in a pond
just before courtship began. Brumwell suggested that pressure on the
plastron of the male had forced the water out his nostrils. The pair
remained in the coital position for 30 minutes after the male had
achieved intromission. In another instance, Brumwell (_loc. cit._) saw
four males pursuing a single female, the males exhibiting the same
behavior (nudging and lunging) outlined above. Males that attempted to
mount other males were repelled by defensive snapping of the
approached male. The female also snapped at some of the males that
tried to mount her. One male was finally successful in mounting and
was henceforth unmolested by the other males. Brumwell suggested that
shell biting and tapping may be methods of sex-recognition.
In the several instances of mating that I observed, the male, after
mounting the shell of the female (Pl. 28), gripped her, with the first
claws of his hind feet, just beneath her legs or on the skin of the
gluteal region and, with the remaining three claws, gripped the
posterior edges of her plastron. In most instances the female secured
the male's legs by hooking her own legs around them. The coital
position of _T. ornata_ seems to differ from that of _T. carolina_, at
least in regard to the position of the male's legs. The coital
positions of _T. carolina_ illustrated by Cahn (1937:94, Fig. 13) are
physically impossible for _T. ornata_.
In _T. ornata_ the pressure exerted on the male's legs by the female
probably impairs circulation and probably is painful to the male,
especially after coitus, when the male falls backward but is still
held by the female. The heavily developed musculature of the legs of
males may be an adaptation to strengthen the legs for this temporary
period of stress. Evans (1953:191) and Cahn and Conder (1932:87-88)
observed the hind legs of males of _T. carolina_ to be noticeably
weakened after copulation, causing the males to remain inactive for
several hours.
Evans (_op. cit._) observed 72 matings of _T. carolina_ and divided
the process into three phases as follows: 1) circling, pushing and
biting by the male; 2) mounting (female with shell closed); and, 3)
coition (female with shell open). Penn and Pottharst (1940:26)
reported that captive _T. carolina_ in New Orleans mated chiefly under
conditions of optimum temperature (21 to 27° C.) and high humidity;
some matings took place in a pool of water. Males pushed females about
after mating, often rolling them over several times.
Because ornate box turtles observed by me were able easily to right
themselves from an inverted position on substrata of all kinds, males
left lying on their backs after copulation are probably in no danger
of perishing in this position, as was suggested by Allard (1939) for
_T. carolina_.
Insemination
Oviducts of several females were flushed by means of a pipette to
determine whether they contained sperm. Approximately half of the
females captured in May, 1956, had sperm in their oviducts, but
females captured in June and July did not. Sperm flushed from the
oviducts were in clumps of several hundred and showed no sign of
motility a few minutes after the female was anesthetized with
chloroform. No sperm were found in the oviducts of immature females
but one female of nearly adult size was observed in copulation with a
mature male.
Thorough examination of microscopic sections of oviduct (taken at
various times in the season of activity) usually revealed a few sperm
lodged in the folds (Pl. 19, Fig. 8) of the cephalic as well as the
caudal portion of the tube, but no specialized seminal receptacles
such as occur in snakes (Fox, 1956) were present. Fertilization
without reinsemination probably occurs in _T. ornata_. Ewing (1943)
and Finneran (1948:126) reported that females of _T. carolina_
produced fertile eggs for periods of four and two years, respectively,
after being removed from all contact with males.
Sexual Cycle of Males
Testes were preserved in each month from April to October. The
following description of spermatogenesis is based chiefly on material
collected in 1955, although testes were preserved also in 1954.
Comparison of material obtained in 1954 and 1955 revealed that
spermatogenesis began earlier and was more advanced on any given date
in 1955 than in 1954.
Testes of mature individuals are pale yellow and slightly oblong. The
epididymis is ordinarily dark brown or black and contrasts sharply
with the color of the testes. Size of testes was expressed as the
average length (greatest diameter) of both testes. Testes are smallest
in April, immediately after emergence from hibernation, and largest in
early September (Pl. 20, Figs. 3-4). They are nearly spherical when of
maximum size; increase in bulk, therefore, is relatively greater than
the increase in size shown in Figure 3. They increase in size from
April until early June, recede during most of June, and again increase
in size in July and August. They remain large from early September
until hibernation is begun, becoming only slightly smaller in late
September and October.
Increase in size following emergence from hibernation may be due in
part to proliferation of the sustentacular cytoplasm. Decrease in size
in early June is correlated with the end of the period of most active
mating; maximal size is coincident with the peak of the spermatogenic
cycle in early September.
[Illustration: FIG. 3. Seasonal fluctuations in size (average
greatest diameter) of testes in _T. o. ornata_ as determined
by examination of 40 specimens from eastern Kansas.]
Spermatogenesis (refer to Pl. 19, Figs. 1-5) begins in early May when
a few spermatogonia appear in the seminiferous tubules. The
histological appearance of testes preserved in April and May is much
the same. Nuclei of Sertoli cells, which outnumber the spermatogonia,
are evident at the periphery of the tubules and the clear cytoplasm of
the cells extends into and nearly fills the lumina. The few darkly
stained spermatids that are present in April are cells that probably
were produced in the previous summer. Sperm are present in small
groups within the sustentacular cytoplasm, but ordinarily are absent
in the lumina.
Primary spermatocytes appear in the tubules from mid-May to early
June. By mid-May there are practically no sperm at any place in the
tubules. The sustentacular cytoplasm has a less compact arrangement in
late May than in April.
Spermatogenesis is well under way by mid-June; at this time, two or
three distinct layers of primary and secondary spermatocytes are
present and these cells outnumber the Sertoli cells. The lumina are
filled with cellular detritus and are no longer bordered by a clear
ring of sustentacular cytoplasm. No sperm are present.
Spermatids appear in late June and a few of them undergo metamorphosis
in early July; by mid-July, spermatids and secondary spermatocytes are
the dominant cells in the seminiferous tubules, although
spermatogonia are still active.
By late August, clusters of sperm and metamorphosing spermatids
surround the Sertoli cells; large numbers of sperm as well as sloughed
cells representing various spermatogenic stages are present in the
lumina. Secondary spermatocytes are still evident near the periphery
of the tubules but they are much less numerous than spermatids. The
germinal epithelium is still semiactive and small groups of primary
spermatocytes are present in nearly all of the tubules.
The spermatogenic cycle is completed in the latter half of October
when most of the spermatozoa pass into the epididymides. A few
spermatozoa and spermatids remain in the seminiferous tubules during
hibernation. Although no testicular material was obtained from
hibernating turtles, comparisons of sections made in October and April
show that the germinal epithelium remains inactive from autumn until
spring. Possibly some spermiogenesis takes place in the early phases
of hibernation or in the period in late autumn when turtles are
intermittently active. It is uncertain whether the reorganization of
the sustentacular cytoplasm occurs in autumn, in spring, or in the
course of hibernation.
The seminiferous tubules of immature males are small, lack lumina, and
contain a few large but inactive spermatogonia (Pl. 19, Fig. 6). The
testes of specimens that were nearly mature contained primary and
secondary spermatocytes but lacked lumina; it was thought that such
individuals would have matured in the following summer and bred in the
following autumn.
Mature sperm were found in epididymides at all times of the year but
were most numerous in spring and autumn, the period between
spermatogenic cycles (Pl. 19, Fig. 7). Sperm expelled from the
epididymides in autumn matings are seemingly replaced by others from
the seminiferous tubules; the epididymides become much smaller when
their supply of sperm is nearly exhausted after spring mating.
Risley (1938:304) found the testes of the common musk turtle,
_Sternotherus odoratus_, to be largest in August and smallest in early
May. Recession of testes in spring was coincident with the period of
active breeding; increase in size, later in the season, corresponded
to increasing spermatogenic activity and enlargement of seminiferous
tubules. Altland (1951:600-603) found the spermatogenic cycle of
_Terrapene carolina_ to be nearly like that of _Sternotherus
odoratus_. Fox (1952) found that testes of garter snakes (_Thamnophis
sirtalis_ and _T. elegans_) in California reached a peak of
spermatogenic activity in midsummer, regressed in the latter half of
the summer, and were inactive in winter.
The spermatogenic cycle of _T. ornata_ as here reported, differs in no
important respect from those of _Thamnophis_, _Sternotherus odoratus_,
or _Terrapene carolina_, except that in _T. ornata_ the cycle begins
and ends somewhat later in the season of activity. In most of the
lizards that have been studied (Fox, 1952:492-3), spermatogenesis
reaches a peak in spring (more or less coincident with the mating
period and with ovulation) and the germinal epithelium remains active
in winter. _Sternotherus_, _Terrapene_, and _Thamnophis_ are alike in
completing spermatogenesis late in the season and storing spermatozoa,
in the seminiferous tubules or in the epididymides, during
hibernation.
It is noteworthy that, in the turtles and snakes mentioned above,
sperm produced in autumn are used to fertilize eggs laid in the
following year, and mating [with the exception of _Thamnophis
elegans_, (Fox, 1956)] occurs in both spring and autumn. It is not
definitely known in any of these instances, whether sperm resulting
from autumn or spring inseminations (or both) fertilize the eggs.
Risley (1933:693) found motile sperm in the oviducts of female
_Sternotherus odoratus_ that had recently emerged from hibernation;
he believed that spring mating, although it commonly occurred, was not
necessary to fertilize eggs. Disadvantages, if any, of completing
spermatogenesis well in advance of ovulation seem to be at least
partly counteracted by two annual mating periods or by mating
throughout the season of activity.
Sexual Cycle of Females
The following account of oögenesis is based on examination of
preserved ovaries from 68 mature specimens. The ages of most specimens
were known, inasmuch as the specimens were used in studies of growth
as well as gametogenesis. Other data were obtained from adult females
that were dissected but not preserved, and from immature females.
[Illustration: FIG. 4. Seasonal fluctuations in ovarian weight
in _T. o. ornata_, as determined by examination of 60 specimens
from eastern Kansas.]
Size of ovarian follicles was determined by means of a clear plastic
gauge containing notches 5, 10, 15, 20, and 25 millimeters wide. The
number of follicles within a given size range could be quickly
determined by finding the smallest notch into which the follicles fit.
It was necessary to weigh all ovaries after preservation since some of
them had not been weighed when fresh. Since all ovarian samples were
preserved in the same manner, weights remained relatively the same.
Preserved material was lighter than fresh by an average of 13 per
cent. Follicles less than one millimeter in diameter were not counted.
Corpora lutea and corpora albicantia were studied under a binocular
dissecting microscope. No histological studies were made of the female
reproductive system.
Ovarian follicles and oviducal eggs were recorded separately for the
right and left sides. Each ovary was always kept associated with the
oviduct of the same side, but in some instances it was not recorded
whether the organs were left or right.
Ovaries ordinarily weighed most in October, March, and April, when
most females contained enlarged follicles, and least in August and
September when the supply of enlarged follicles was usually exhausted
(Figs. 4 and 5).
[Illustration: FIG. 5. The seasonal occurrence of enlarged
ovarian follicles in females of _T. o. ornata_, expressed,
For each month, as the percentage of total females that
contained two or more follicles having diameters greater than
15 mm. Total number of females in each of the samples is shown
in parentheses at the top of each bar.]
The ovarian cycle begins in July or August, after ovulation has
occurred. At that time many minute follicles form on the germinal
ridges of the ovaries. On the basis of the material that I examined,
it seems that ovarian follicles either grow to nearly mature size in
the season preceding ovulation and remain quiescent over winter or
grow rapidly in the period of approximately six weeks between spring
emergence and ovulation. Altland (1951:603-5) reported that the former
condition was the usual one in _T. carolina_; he suggested that
possibly some of the enlarged follicles were absorbed during
hibernation.
Examination of yolks of oviducal eggs revealed that follicles mature
when they reach a diameter of 16 to 20 millimeters and a weight of two
to two and one-half grams (Pl. 20, Fig. 1).
The enlarged follicles remaining on the ovaries after ovulation
(excluding those smaller than six mm.) can be grouped according to
diameter as: large (greater than 15 mm.), medium (11 to 15 mm.), and
small (six to 10 mm.). Ten females collected in the period from June 2
to 8, after they had ovulated, all had follicles falling in at least
one of these size groups, and eight had follicles falling in two or
more of the groups. In females having enlarged follicles of more than
one of the size groups, there were several follicles in each of two
groups and no follicles, or only one follicle, in the remaining group.
Enlarged follicles represent future clutches but whether the enlarged
follicles will be ovulated in the same season or in a later season is
questionable.
Evidence found in the present study suggested that at least a few
females lay more than one clutch of eggs per year. Among 34 specimens
obtained in June and July, eight (24 per cent) had corpora lutea (or
easily discernible corpora albicantia) and at least two follicles more
than 15 millimeters in diameter; in three specimens (9 per cent) the
ovaries bore fresh corpora lutea (representing recent ovulations) and
a set of older corpora lutea (representing ovulations that had
occurred several weeks previously). It was thought that each of these
eleven females (33 per cent of sample) had produced or would have
produced two clutches of eggs in the season of its capture. The number
of large follicles present after the first set of ovulations (mean,
3.5) was fewer in most instances than the average clutch-size (see
below), indicating that second clutches are smaller than first
clutches. Smaller second clutches were found also in _T. carolina_
(Legler, 1958).
Further evidence for multiple clutches was the absence of enlarged
ovarian follicles in some females obtained in September. Atretic
follicles, ordinarily orange, brown, or purplish, were observed on the
ovaries of many of the females examined; in most instances, not more
than two follicles of the small or medium size groups were atretic.
Atresia was in no instance great enough to account for the complete
loss of enlarged follicles.
Further study probably will show that many of the females laying in
May and early June lay again before the end of July, and that eggs in
the oviducts of females captured in the latter month frequently
represent second clutches. Under favorable conditions, eggs laid by
the end of July would have a good chance of hatching before the advent
of cold weather in autumn; turtles hatching too late to escape from
the nest could burrow into its sides and probably escape freezing
temperatures.
Cagle's findings concerning _Pseudemys scripta_ (1950:38) and
_Chrysemys picta_ (1954:228-9) suggest that these species lay more
than one clutch per season, at least in the southern parts of their
ranges. Carr (1952) indicated that multiple layings were known in most
species of marine turtles (families Dermochelydae and Chelonidae) and
strongly suspected in other species. Other turtles recorded to have
produced multiple clutches in a single season (based chiefly on
captive specimens or cultured populations) include: the starred
tortoise, _Geochelone elegans_ (Deraniyagala, 1939:287); the Asiatic
trionychid, _Lissemys punctata_ (_op. cit._:304); the diamond-backed
terrapin, _Malaclemys terrapin_ (Hildebrand and Prytherch, 1947:2);
and the Japanese soft-shelled turtle, _Trionyx japonicus_ (Mitsukuri,
1895, cited by Cagle, 1950:38).
There is a marked alternation of ovarian activity in _T. ornata_, one
ovary being more active than its partner in a given season. The less
active ovary is more active than its partner in the following season.
For example, a specimen killed in July had four corpora lutea on the
right ovary and two on the left and there were five enlarged follicles
(of the medium size group), representing the next set of eggs to be
ovulated, four on the left ovary and one on the right. Similar
alternation of ovarian activity was observed, to a greater or lesser
extent, in nearly all of the females examined. Many subadult females
that were approaching their first breeding season (as evidenced by the
presence of large ovarian follicles but no indication of former
ovulation) had but one active ovary. This may account in part for the
tendency of small, young females to lay clutches smaller than average.
One ovary may become senile in old females before its partner does;
this may explain the occasional absence or atrophy of one ovary in
large females that I have examined.
In all the specimens examined, it was evident that ovulation had
occurred or would occur in two successive seasons. Senile or young
females might, however, be expected to skip a laying season if only
one ovary was functioning.
After ovulation, the collapsed follicle assumes a cuplike shape and
becomes a glandular corpus luteum (Pl. 20, Fig. 2). Corpora lutea are
approximately eight millimeters in diameter and are easily discernible
at least until the eggs are laid; they are somewhat less distinct
after preservation. Corpora lutea undergo rapid involution following
oviposition and, after two to three weeks, are little more than small
puckerings on the ovarian epithelium. At this stage they are properly
referred to as corpora albicantia and are discernible only after
careful examination of the ovary under low magnification. Corpora
albicantia remain on the ovary until April of the year following
ovulation but disappear in May and are never present after the new set
of eggs is ovulated. Ovaries of some subadults (that would have laid
first in the season following capture) contained enlarged follicles
and, but for their lack of corpora lutea and corpora albicantia, were
indistinguishable from those of older, fully mature females.
Altland (1951:605-610) gave a histological description of the corpus
luteum of _Terrapene carolina_. Corpora lutea were glandular and
filled with lipoidal material until the eggs were laid. Atresia of
corpora lutea began when eggs were laid, was completed by mid-August,
and was coincident with atresia of large follicles that did not
undergo ovulation. Altland did not describe the gross external
appearance of the corpus albicans.
The corpus luteum of oviparous reptiles seems to be closely associated
with the intrauterine life of the eggs and, in viviparous reptiles, it
may be an important factor in maintaining optimum gestational
environment; however, its functions in all reptiles are poorly
understood (Miller, 1948:200-201).
Information gleaned from records of gravid females and known dates of
nesting suggests that eggs are retained in the oviducts two to three
weeks before laying. Once they are ovulated, the eggs are exposed to
but few hazards until laid; counts of corpora lutea are an accurate
indication of the number of eggs laid. In the gravid females examined
by me, number of corpora lutea on the ovaries was equal, in all but
one instance, to the number of oviducal eggs. In the single instance
in which an extra corpus luteum was found, one egg had probably been
laid before the specimen was captured. The high incidence of
correspondence between counts of corpora lutea and counts of oviducal
eggs indicates also that _T. ornata_ deposits the entire complement of
oviducal eggs at one time, not singly or in smaller groups.
Extrauterine migration of ova, whereby eggs from one ovary pass into
the oviduct of the opposite side, is of common occurrence in _T.
ornata_ and is known to occur also in _T. carolina_, _Chrysemys
picta_, _Emydoidea blandingi_, _Pseudemys scripta_, _Cnemidophorus
sexlineatus_, and in several mammals (Legler, 1958). This ovular
migration may serve to redistribute eggs to the oviducts when the
ovaries are functioning at unequal rates.
The eggs acquire shells soon after they enter the oviducts. No
shell-less eggs were found in oviducts but several specimens of _T.
ornata_ had oviducal eggs, the thin, parchmentlike shells of which
lacked the outer calceous layer; in these specimens the corpora lutea
were fresh, probably not more than two days old. Eggs that had
remained in the oviducts longer had a calceous layer on the outside of
the shell. Eggs having incompletely developed shells were successfully
incubated in the laboratory. Cagle (1950:38) found shelled but
yolkless eggs in the oviducts of several _Pseudemys scripta_ but found
no yolkless eggs in nests. No yolkless eggs were found in specimens of
_T. ornata_ in the course of the present study.
The uterine portion of the oviducts becomes darkened (pale gray to
intense black) in the breeding season. Darkening of oviducts seemed to
coincide with the period when eggs were in the oviducts and it
persisted for a variable length of time after the eggs were laid.
Oviducts of immature females were ordinarily pale.
Nesting
Ornate box turtles nest chiefly in June. Some females nest as early as
the first week of May or as late as mid-July but the nesting season
reaches its peak in mid-June. Eggs nearly ready to be laid were in
oviducts (determined by bimanual palpation in the field or by
dissection in the laboratory) of many females captured in June; nearly
half of the records so obtained were in the second week of that month.
Early records of shelled oviducal eggs were April 25 (specimen from
Ottawa County, Oklahoma), May 5, and May 22. The two latest records
are for females retaining oviducal eggs on July 2 and 11. Known dates
for nesting of free-living females were distributed rather evenly
through the month of June. It is worthy of note that all (four) of
the nestings known to occur in July were by captive females. Females
of _T. ornata_, like those of some other turtles (Cagle and Tihen,
1948; Risley, 1933:694), seem to retain their eggs until conditions
are suitable for nesting. Most of the reports in the literature of
nesting after mid-July represent records for captive females.
Nests of _T. o. ornata_ were so well-concealed that they were
difficult to find even when a gravid female had been followed to the
approximate location by means of a trailing thread. Females spend one
to several days seeking a site for the nest, usually traveling a
circuitous route within a restricted area. Movements of nest-seeking
females were more extensive than those of males and non-gravid females
observed in the same periods.
Activities of one gravid female, typical in most respects of the
activities of several other gravid females observed (for periods of
one to 23 days) at the Damm Farm, illustrate pre-nesting behavior
(Fig. 29). A trailer was attached to the female on the morning of June
7. She was recovered early on the following afternoon; her movements
in the elapsed period had been restricted to a small, deep, ravine 150
feet long and 20 to 30 feet wide. She had traversed each edge of the
ravine at least once and had crossed it six or seven times, keeping
mostly to areas on the upper parts of south--or west--facing slopes
where vegetation was sparse or lacking. In six places she had dug into
the ground, probably to test the suitability of the soil for nesting.
In three places she dug beneath rocks that jutted out from the bank,
and in two places merely scratched away the upper crust of soil. Her
most recent attempt at digging (probably late the previous evening or
in early morning on the day of her capture) consisted of a
flask-shaped cavity that, but for the lack of eggs and a covering of
earth, was like a completed nest (Pl. 21, Fig. 1). The cavity was 55
millimeters deep, 80 millimeters wide at the bottom, and 60
millimeters wide at the opening. For several inches about the opening
the earth was slightly damp. That piled on the rim of the opening was
of the consistency of thick mud, indicating that the female had voided
fluid first on the surface of the earth and again inside the cavity to
soften the soil. Subsequently during eight days her activities were
similar but not so extensive as on the day described above. It was
determined by daily palpation that she laid her eggs somewhere in the
general area of the ravine on June 15 but the nest could not be found.
No completed nests containing eggs were discovered at the Damm Farm
but the locations of several robbed nests and partly completed nests
provided some information on preferred sites. The nests found were on
bare, well-drained, sloping areas and were protected from erosion by
upslope clumps of sod or rocks. The nest cavity illustrated in Plate
21 was at the edge of the sod-line on the upper lip of the west-facing
bank of a ravine. One nest had been excavated in a shallow den beneath
an overhanging limestone rock. Three nests were on west- or
south-facing slopes and one was on the north-facing bank of a ravine.
Box turtles presumably select bare areas for nesting because of the
greater ease of digging. One female at the Damm Farm was thought to
have laid her eggs in a cultivated field and William R. Brecheisen
told me he discovered two nests in a wheat field being plowed in July,
1955.
The repeated excavation of trial nest cavities presumably exhausts the
supply of liquid in the female's bladder. Frequent imbibing of water
is probably necessary if the search for a nesting site is continued
for more than a day or two. Standing water was usually available in
ponds, ravines, ditches, and other low areas at the Damm Farm in June.
Nesting in June, therefore, is advantageous not only because of the
greater length of time provided for incubation and hatching but also
because of the amount of water available for drinking. Females can
probably be more selective in the choice of a nesting site if their
explorations are not limited by lack of water.
Females of _T. ornata_, in all instances known to me, began excavation
of their nests in early evening and laid their eggs after dark; Allard
(1935:328) reported the same behavior for _T. carolina_.
William R. Brecheisen, on July 22, 1955, at his farm, two miles south
and one mile west of Welda, Anderson County, Kansas, observed that a
large female began digging a nest in an earth-filled stock tank at
6:00 P. M. At first she moved her body about on the surface of the
earth, loosening it and pushing it aside with all four legs, making a
depression approximately two inches deep and large enough to
accommodate her body. At 7:30 P. M. she began digging alternately with
her hind feet at the bottom of the depression. Digging continued until
10:00 P. M., at which time the nest cavity was three inches deep, and
three inches in diameter, with a smaller opening at the top. Six eggs
were laid in the next half-hour. Covering of the nest probably took
more than one hour but observations were terminated after the final
egg was laid. By the following morning the nest-site had been
completely covered and was no different in appearance from the rest of
the earthen floor of the tank. (Brecheisen observed more of the
nesting than anyone else has recorded and I am obliged to him for
permission to abstract, as per the above paragraph, the notes that he
wrote on the matter.)
A nest made by a captive female at the Reservation was of normal
proportions except for an accessory cavity that opened from the neck
of the nest, immediately below the surface of the ground. This smaller
cavity contained a single egg. This peculiar nest may have resulted
from the efforts of two different females since several were kept in
the same outdoor pen.
Ten adult females were kept in an outdoor cage in the summer of 1955.
The cage was raised off the ground on stilts and its floor was covered
with 12 inches of black, loamy soil. A small pan of water was always
available in the cage and the turtles were fed greens, fruit, and
table scraps each evening. Nesting activity was first noted on June
21, when one of the females was digging a hole in a corner of the
enclosure. She dug with alternate strokes of her fully-extended hind
legs in the manner described (Legler, 1954:141) for painted turtles
(_Chrysemys picta bellii_). Nevertheless, digging was much less
efficient than in _Chrysemys_, because of the narrow hind foot of the
female _T. ornata_; approximately half of the earth removed by any one
stroke rolled back into the nest or was pulled back when she
reinserted her leg. The female stopped digging when I made sudden
movements or held my hand in front of her. Digging continued for
approximately 45 minutes; then the female moved away and burrowed
elsewhere in the cage. The nest cavity that she left was little more
than a shallow depression. Three other females were digging nests
early in the evening on July 3, 5, and 8; in each of these instances
the female stopped digging to eat when food was placed in the cage and
completed the nesting process, unobserved, later in the evening. In
each instance where nest-digging by captive females was observed, the
hind quarters of the female rested in a preliminary, shallow
depression, and the anterior end of the body was tilted upward at an
angle of 20 to 30 degrees. In late June and early July several eggs
were found, unburied, on the floor of the cage and in the pan of
water.
The excavation of a preliminary cavity by captive females may not
represent a natural phenomenon. Allard (1935) made no mention of it in
his meticulous description of the nesting process in _T. carolina_. It
is worthy of mention, however, that Booth (1958:261) reported the
digging of a preliminary cavity by a captive individual of _Gopherus
agassizi_.
Eggs
The number of eggs in 23 clutches ranged from two to eight (mean, 4.7
± 1.37 [sigma]); clutches of four, five, and six eggs were most
common, occurring in 18 (78 per cent) instances. The tendency for
large females to lay more eggs than small females (Fig. 6) was not so
pronounced as that reported by Cagle (1950:38) for _Pseudemys
scripta_. The small size of _T. ornata_, in comparison with other
emyid turtles, seemingly limits the number of eggs that can be
accommodated internally. The number of eggs per clutch in T. carolina
[2 to 7, average 4.2, Allard (1935:331)], is nearly the same as that
of _T. ornata_.
[Illustration: FIG. 6. The relation of plastral length to
number of eggs laid by 21 females of _T. o. ornata_ from
eastern Kansas.]
Shells of the eggs are translucent and pinkish or yellowish when the
eggs are in the oviducts. After several days outside the oviducts the
shells become chalky-white and nearly opaque. Eggs incubated in the
laboratory retained the pinkish color somewhat longer than elsewhere
on their under-surfaces, which were in contact with moist cotton, but
eventually even this part of the shell became white. Infertile eggs
remained translucent and eventually became dark yellow, never becoming
white; they could be distinguished from fertile eggs on the basis of
color alone. Shells of infertile eggs became brittle and slimy after
several weeks.
The outer layer of the shell of a freshly laid egg is brittle and
cracks when the egg is dented. After a few days, when the eggs begin
to expand, the shell becomes flexible and has a leathery texture. The
shell is finely granulated but appears smooth to the unaided eye. The
granulations are approximately the same as those illustrated by
Agassiz (1857:Pl. 7, Fig. 18) for _T. carolina_.
Eggs are ellipsoidal. Data concerning size and weight (consisting of
mean, one standard deviation, and extremes, respectively) taken from
42 eggs (representing 9 clutches) within 24 hours after they were
laid, or dissected from oviducts, are as follows: length, 36.06 ± 2.77
(31.3-40.9); width, 21.72 ± 1.04 (20.0-26.3); and weight, 10.09 ± 1.31
(8.0-14.3). There was a general tendency for smaller clutches to have
larger eggs; the largest and heaviest were in the smallest clutch (two
eggs) and the smallest were in the largest clutch (eight eggs). Risley
(1933:697) reported such a correlation in _Sternotherus odoratus_, as
did Allard (1935:331) in _T. carolina_. Measurements in the literature
of the size of eggs of _T. ornata_ suggest a width greater than that
stated above, probably because some eggs already had begun to expand
when measured.
Eggs of _T. ornata_ expand in the course of incubation, as do other
reptilian eggs with flexible shells, owing to absorption of water. In
the laboratory, 48 eggs increased by an average of approximately three
grams in weight and three millimeters in width over the entire period
of incubation; increase in width coincided with decrease in length.
Cotton in incubation dishes was kept moist enough so that some water
could be squeezed from it. When the cotton was constantly moist, eggs
showed a fairly steady expansion from the first week of incubation
until hatching. The process could be reversed by allowing the cotton
to dry. Eggs that were allowed to dry for a day or more became grossly
dented or collapsed. Eggs at the periphery of the incubation dish were
ordinarily more seriously affected by drying than were those at the
center or in the bottom of the dish. A generous re-wetting of
desiccated eggs and cotton caused the eggs to swell to their original
proportions within 24 hours. Recessions occurred, however, even in the
clutches that received the most nearly even amount of moisture.
Increases in weight and size seemed to reach a peak in the middle of
the incubation period and again immediately before hatching. Infertile
eggs expanded in the same manner as fertile eggs in the first week or
two of incubation, but thereafter gradually regressed in bulk or
failed to re-expand after temporary periods of dryness. Fertile eggs
that were in good condition had a characteristically turgid, springy
feel and could be bounced off a hard surface.
Temporary lack of moisture usually did not kill embryos; prolonged
dryness, combined with high temperatures, probably could not be
tolerated. Lynn and Ullrich (1950), by desiccating the eggs of
_Chrysemys picta_ and _Chelydra serpentina_, produced abnormalities in
the young ranging from slight irregularities of the shell to eyeless
monstrosities; eggs desiccated in the latter half of incubation
produced a higher percentage of abnormal young than eggs that were
desiccated earlier.
In 1956, three fertile eggs, from clutches that were at different
stages of incubation, were immersed in water for 48 hours. The eggs
rested on the bottom of the bowl in the same position in which they
had been placed in the incubation dishes; when turned, they returned
invariably to the original position. The embryos in two of the eggs
(one and 27 days old at the time of immersion) were still living ten
days after the eggs were removed from the water; the embryo in the
remaining egg (21 days old at the time of immersion) was dead. Eggs
immersed in water increased in size and weight at the same rate as
eggs in incubation dishes, indicating that absorption of water
probably operates on a threshold principle, the amount absorbed being
no more than normal even under wet conditions.
Natural nests usually are in well-drained areas, but water probably
stands in some nests for short periods after heavy rains. Provided the
nest cavity itself is not damaged, water in the nest is probably more
beneficial than harmful to the eggs; however, nests that are inundated
during floods probably have little chance of survival.
Embryonic Development
Eggs were examined by transmitted light in the course of incubation.
At the time of laying (or removal from oviducts) no embryonic
structures were discernible even in eggs that had been retained in the
oviducts of captive females some weeks past the normal time of laying;
a colorless blastodisc could be seen if eggs were opened. Embryonic
structures first became visible at eight to ten days of incubation; at
this time vascularization of the blastodisc was evident and the eyes
appeared as dark spots. Heart beats were observed in most embryos by
the fifteenth day but were evident in a few as early as the tenth day.
The pulse of a fifteen-day-old embryo averaged 72 beats per minute at
a temperature of 30 degrees. Embryos at fifteen days, measured in a
straight line from cephalic flexure to posteriormost portion of body,
were approximately nine to ten millimeters long and at 22 days were 14
millimeters long. At approximately 35 days the eggs became dark red;
embryonic structures were discernible thereafter only in eggs that had
embryos situated at one end, close to the shell.
Incubation periods for 49 eggs (representing 12 clutches) kept in the
laboratory ranged from 56 to 127 days, depending on the temperature of
the air during the incubation period. In 1955, eggs were kept at my
home in Lawrence where air temperatures were uncomfortably hot in
summer and fluctuations of 20 degrees (Fahrenheit) or more in a
24-hour period were common. The following summer eggs were kept in my
office at the Museum where temperatures were but slightly cooler than
in my home and subject also to wide variation. In 1957 this part of
the Museum was air-conditioned and kept at approximately 75 degrees.
The greater lengths of incubation periods at lower temperatures are
shown in Table 1. Risley (1933:698) found the incubation period of
_Sternotherus odoratus_ to be longer at lower temperatures;
corresponding observations were made by Allard (1935:332) and Driver
(1946:173) on the eggs of _Terrapene carolina_. Cagle (1950:40) and
Cunningham (1939) found no distinct differences in length of
incubation period for eggs of _Pseudemys scripta_ and _Malaclemys
terrapin_, respectively, at different temperatures within the range
tolerated by the eggs.
Most nests observed in the field were in open situations where they
would receive the direct rays of the sun for at least part of the day;
the shorter average incubation periods (59 and 70 days, respectively),
observed in 1955 and 1956, therefore, more nearly reflect the time of
incubation under natural conditions than does the excessively long
period (125 days at 75 degrees) observed in 1957 under cooler, more
nearly even temperatures.
TABLE 1.--The Relationship of Temperature and Duration of Incubation
Period as Determined from Laboratory Studies of 49 Eggs of
_T. ornata_.
=============+===================+=========+========+=================
Average | Period of | Number | Number |
daily | incubation (Days) | of | of | Remarks
temperature |--------+----------|clutches | eggs |
(Fahrenheit) | Mean | Range | | |
-------------+--------+----------+---------+--------+-----------------
| | | | | Wide daily
91 | 59 | 56-64 | 6 | 24 | fluctuations in
| | | | | temperature
-------------+--------+----------+---------+--------+-----------------
| | | | | Wide daily
82 | 70 | 67-73 | 4 | 21 | fluctuations in
| | | | | temperature
-------------+--------+----------+---------+--------+-----------------
| | | | | Temperature
75 | 125 | 124-127 | 2 | 4 | thermostatically
| | | | | controlled
-------------+--------+----------+---------+--------+-----------------
Sixty-five days seems to be a realistic estimate of a typical
incubation period under natural conditions; eggs laid in mid-June
would hatch by mid-August. Even in years when summer temperatures are
much cooler than normal, eggs probably hatch by the end of October.
Hatchlings or eggs would have a poor chance of surviving a winter in
nests on exposed cut-banks or in other unprotected situations.
Overwintering in the nest, hatchlings might survive more often than
eggs, since hatchlings could burrow into the walls and floor of the
nest cavity. Unsuitable environmental conditions that delay the
nesting season and retard the rate of embryonic development may, in
some years, be important limiting factors on populations of ornate box
turtles.
In areas where _T. ornata_ and _T. carolina_ are sympatric (for
example, in Illinois, Kansas, and Missouri) the two species occupy
different habitats, _ornata_ preferring open grassland and _carolina_
wooded situations. Under natural conditions, the average incubation
periods of these two species can be expected to differ, _T. carolina_
having a somewhat longer period due to lower temperatures in nests
that are shaded. In the light of these speculations, the remark of
Cahn (1937:102)--that _T. ornata_ nested later in the season (in
Illinois) and compensated for this by having a shorter incubation
period--is understandable.
The range of temperatures tolerated by developing eggs probably varies
with the stage of embryonic development. When temperatures in the
laboratory were 102 to 107 degrees Fahrenheit for approximately eight
hours, due to a defect in a thermostat, the young in two eggs of _T.
ornata_, that had begun to hatch on the previous day, were killed, as
were the nearly full-term embryos in a number of eggs of _T. carolina_
(southern Mississippi) kept in the same container. A five-day-old
hatchling of _T. ornata_, kept in the same container, survived the
high temperatures with no apparent ill effects. Cagle (1950:41) found
that eggs of _Pseudemys scripta_ could not withstand temperatures of
10 degrees for two weeks nor would they survive if incubated at 40
degrees. Cunningham (1939) reported that eggs of _Malaclemys terrapin_
could not survive prolonged exposure to temperatures of 35 to 40.6
degrees but tolerated temporary exposure to temperatures as high as
46 degrees.
In the summer of 1955, a clutch of three eggs, all of which contained
nearly full-term embryos, was placed in a refrigerator for 48 hours.
The temperature in the refrigerator was maintained at approximately
4.5 degrees; maximum and minimum temperatures for the 48 hour period
were 2.8 and 9.5 degrees, respectively. When the eggs were removed
from the refrigerator they showed gains in weight and increases in
size comparable to eggs, containing embryos of the same age, used as
controls. The experimental eggs began to hatch two days after they
were removed to normal temperatures--approximately 24 hours later than
the controls.
In the late stages of incubation, the outer layer of the shell becomes
brittle and is covered with a mosaic of fine cracks or is raised into
small welts. Several days before hatching, movements of the embryo
disturb the surface of the shell and cause the outer layer to crumble
away, especially where the head and forequarters of the embryo lie
against the shell. Some embryos could be seen spasmodically thrusting
the head and neck dorsally against the shell.
The role of the caruncle in opening the shell seems to vary among
different species of turtles. Cagle (1950:41) reported that it was
used only occasionally by _Pseudemys scripta_; Allard (1935:332)
thought that it was not used by _Terrapene carolina_; and, the
observations of Booth (1958:262) and Grant (1936:228) indicate that
embryos of _Gopherus agassizi_ use the caruncle at least in the
initial rupturing of the shell.
In the three instances in which hatching was closely observed in _T.
ornata_, the caruncle made the initial opening in the shell; claws of
the forefeet may have torn shells in other hatchings that were not so
closely observed. In all observed instances, the shell was first
opened at a point opposite the anterior end of the embryo. The initial
opening had the appearance of a three-cornered tear. A quantity of
albuminous fluid oozed from eggs as soon as the shells were punctured.
The initial tear is enlarged by lateral movements of the front feet,
and later the hind feet reach forward and lengthen the tear farther
posteriorly. In many instances a tear develops on each side and the
egg has the appearance of being cleft longitudinally. The young turtle
emerges from the anterior end of the shell or backs out of the shell
through a lateral tear.
The process of hatching, from rupture of shell to completion of
emergence, extended over three to four days in the laboratory. Many
hatchlings from time to time crawled back into the shell over a period
of several days after hatching was completed. In a clutch of eggs kept
in a pail of earth, by William R. Brecheisen, eight days elapsed
between onset of hatching and appearance of the first hatchling at the
surface.
A nest in an outdoor pen at the Reservation was discovered in early
October. The cap had been recently perforated and the hatchlings had
escaped. One of them, judged to be approximately two weeks old, was
found in a burrow nearby. The cavity of the nest appeared to have been
enlarged by the young. The eggs were probably laid in early July.
Emergence of young from the nest had been delayed for a time after
hatching, until rain softened the ground in late September and early
October.
Fertility and Prenatal Mortality
Eggs were incubated in the laboratory at more nearly optimum
temperature and humidity than were eggs in natural nests. Percentage
of prenatal mortality probably was lower in laboratory-incubated eggs
than in those under natural conditions.
Of sixty eggs studied in the laboratory, 45 (75 per cent) were
fertile; 36 (80 per cent) of the fertile eggs (those in which the
blastodisc was at some time discernible by transmitted light) hatched
successfully. In six clutches all the eggs were fertile and five of
these clutches hatched with 100 per cent success. One clutch contained
eggs that were all infertile and another clutch had four infertile
eggs and two fertile eggs that failed to hatch. Among nine fertile
eggs that failed to survive, four casualties occurred in the late
stages of incubation or after hatching had begun, indicating that
these are probably critical periods.
Fertility of eggs was not correlated with size or age of female, with
size of clutch, or with size of egg. Eggs laid in the laboratory had
higher rates of infertility and prenatal mortality than did eggs
dissected from oviducts. Handling of eggs in removing them from nests
to incubation dishes, after embryonic development had begun, might
have been responsible for reduced viability (Table 2).
TABLE 2.--Comparative Rates of Fertility and Prenatal Mortality for
Eggs Dissected from Oviducts and for Eggs That Were Laid in the
Laboratory and Subsequently Removed to Incubation Dishes.
===========================+==============+===============
| Eggs removed | Eggs dissected
NUMBER OR PERCENTAGE | from nests | from oviducts
---------------------------+--------------+---------------
Number of eggs examined | 22 | 38
---------------------------+--------------+---------------
Percentage of fertile eggs | 64 | 82
---------------------------+--------------+---------------
Percentage of fertile | |
eggs hatched | 50 | 94
---------------------------+--------------+---------------
Percentage of eggs hatched | 32 | 76
---------------------------+--------------+---------------
Reproductive Potential
Assuming that 4.7 eggs are laid per season, that all eggs are fertile
and all hatch, that all young survive to maturity, that half the
hatchlings are females, and that females first lay eggs in the
eleventh year, the progeny of a single mature female would number 699
after twenty years. Considering that infertility and prenatal
mortality eliminate approximately 40 per cent of eggs laid (according
to laboratory findings) the average number of surviving young per
clutch would be 2.8 and the total progeny, after 20 years, would be
270, provided that only one clutch of eggs was laid per year. But it
is thought that, on the average, one third of the female population
produces two clutches of eggs in a single season. If the second clutch
contains 3.5 eggs (resulting in 2.1 surviving young when factors of
infertility and prenatal mortality are considered), the progeny of a
single female, after 20 years, would number approximately 380.
Postnatal mortality reduces the progeny to a still smaller number.
The small number of eggs laid each year and the long period required
to reach sexual maturity make the reproductive potential of _T.
ornata_ smaller than that of the other turtles of the Great Plains,
and much smaller than nearly any of the non-chelonian reptiles of the
same region.
Number of Reproductive Years
The total span of reproductive years is difficult to determine; I am
unable to ascertain the age of a turtle that has stopped growing. No
clearly defined external characteristics of senility were discovered
in the populations studied. A male that I examined had one atrophied
testis. In another male both testes were shrunken and discolored and
appeared to be encased by fibrous tissue. Both males were large, well
past the age of regular growth, and had smoothly worn shells. Several
old females had seemingly inactive ovaries. Reproductive processes
probably continue throughout life in most members of the population,
although possibly at a somewhat reduced rate in later life.
GROWTH AND DEVELOPMENT
Initiation of Growth
Young box turtles became active and alert as soon as they hatched, and
remained so until low temperatures induced quiescence. If sand or soil
was available, hatchlings soon burrowed into it and became inactive.
Covering containers with damp cotton also induced inactivity; the
hatchlings usually made no attempt to burrow through the confining
layer. Desire to feed varied in hatchlings of the same brood and
seemed not to be correlated with retraction of the yolk sac or
retention of the caruncle. Some hatchlings actively pursued mealworms;
on subsequent feedings they learned to associate my presence with food
and eagerly took mealworms from forceps or from my hand. Meat,
vegetables, and most other motionless but edible objects were ignored
by hatchlings but some individuals learned to eat meat after several
forced feedings. Hatchlings that regularly took food in the first
month of life ordinarily grew faster than hatchlings that did not eat.
Many of the hatchlings in the laboratory showed no areas of new
epidermal growth on the shell in the time between hatching and first
(induced) hibernation.
Size and Appearance at Hatching
The proportions of the shell change somewhat in the first few weeks of
life. At hatching the shell may be misshapen as a result of
confinement in the egg. Early changes in proportions of the shell
result from expansion--widening and, to a lesser degree, lengthening
of the carapace--immediately after hatching. Subsequent retraction or
rupture of the yolk sac and closure of the navel are accompanied by a
decrease in height of shell and slight, further widening of the
carapace.
The yolk sac retracts mainly between the time when the egg shell is
first punctured and the time when the turtle actually emerges from the
shell. When hatching is completed, the yolk sac usually protrudes no
more than two millimeters, but in some individuals it is large and
retracts slowly over a period of several days.
One individual began hatching on November 11 and was completely out of
the egg shell next day; the yolk sac was 15 millimeters in diameter,
protruded six millimeters from the umbilical opening, and hindered
the hatchling's movements. The sac broke two days later, smearing the
bottom of the turtle's dish with semifluid yolk. The hatchling then
became more active. Twenty-six days later the turtle was still in good
condition and its navel was nearly closed. A turtle that hatched with
a large yolk sac in a natural nest possibly would benefit, through
increased ease of mobility, if the yolk sac ruptured.
A recently hatched turtle was found at the Reservation in October,
1954, and was kept in a moist terrarium in the laboratory where it
died the following May. The turtle was sluggish and ate only five or
six mealworms while in captivity; no growth was detectable on the
laminae of the shell. Autopsy revealed a vestige of the retracted yolk
sac, approximately one millimeter in diameter, on the small intestine.
The navel ("umbilical scar") of captive hatchlings ordinarily closed
by the end of the second month but in three instances remained open
more than 99 days. The position of the navel is marked by a
crescent-shaped crease, on the abdominal lamina, that persists until
the plastron is worn down in later years (Pl. 24, Fig. 1).
[Illustration: FIG. 7. A hatchling of _T. o. ornata_ (Ã 2) that
still retains the caruncle ("egg tooth"). A distinct boss will
remain on the maxillary beak after the caruncle is shed.]
The caruncle ("egg tooth") (Fig. 7) remains attached to the horny
maxillary beak for a variable length of time; 93 per cent of the live
hatchlings kept in the laboratory retained the caruncle on the tenth
day, 71 per cent on the twentieth day, and only 10 per cent on the
thirtieth day of life. Few individuals retained the caruncle when they
entered hibernation late in November, and none retained it upon
emergence from hibernation. Activities in the first few days or weeks
of life influence the length of time that the caruncle is retained;
turtles that begin feeding soon after hatching probably lose the
caruncle more quickly than do those that remain quiescent. The
caruncles of some laboratory specimens became worn before finally
dropping off. Almost every caruncle present after 50 days could be
flicked off easily with a probe or fingernail. The initiation of
growth of the horny maxillary beak probably causes some loosening of
the caruncle. The caruncle may aid hatchlings in escaping from the
nest.
After the caruncle falls off, a distinct boss remains, marking its
former place on the horny beak (Pl. 25, Fig. 1); this boss is
gradually obliterated over a period of weeks by wear and by
differential growth, and is seldom visible in turtles that have begun
their first full year of growth. The "first full year of growth" is
here considered to be the period of growth beginning in the spring
after hatching.
Growth of Epidermal Laminae
Growth of ornate box turtles was studied by measuring recaptured
turtles in the field, by periodically measuring captive hatchlings and
juveniles, and by measuring growth-rings on the epidermal laminae of
preserved specimens. Studies of growth-rings provided by far the
greatest volume of information on growth, not only for the years in
which field work was done, but for the entire life of each specimen
examined.
It was necessary to determine the physical nature of growth-rings and
the manner in which they were formed before growth could be analyzed.
Examination of epidermal laminae on the shell of a box turtle reveals
that each has a series of grooves--growth-rings--on its surface. The
deeper grooves are major growth-rings; they occur at varying distances
from one another and run parallel to the growing borders of the
lamina. Major growth-rings vary in number from one to 14 or more,
depending on the age of the turtle (Pl. 22). In juvenal turtles and in
young adults, major growth-rings are distinct and deep. Other grooves
on the shell--minor growth-rings--have the same relationship to the
borders of the laminae but are shallower and less distinct than major
growth-rings. One to several minor growth-rings usually occur on each
smooth area of epidermis between major growth-rings. As the shell of
an adult turtle becomes worn, the minor growth-rings disappear and the
major rings become less distinct. Both sets of rings may be completely
obliterated in old turtles but the major rings usually remain visible
until several years after puberty.
In cross section, major growth-rings are V- or U-shaped. The inner
wall of each groove is the peripheral edge of the part of the scute
last formed whereas the outer wall represents the inner edge of the
next new area of epidermal growth. The gap produced on the surface of
the lamina (the open part of the groove) results from cessation of
growth at the onset of hibernation. Minor growth-rings are shallow
and barely discernible in cross-section (Fig. 8). It may therefore be
understood that growth-rings are compound in origin; each ring is
formed in part at the beginning of hibernation and in part at the
beginning of the following growing season.
The few publications discussing growth in turtles express conflicting
views as to the exact mode of growth of epidermal laminae. Carr
(1952:22) briefly discussed growth of turtle scutes in general and
stated that eccentric growth results from an entirely new laminal
layer forming beneath, and projecting past the edges of the existing
lamina. Ewing (1939) found the scutes of _T. carolina_ to be the
thickest at the areola and successively thinner in the following eight
annual zones of growth; parts of scutes formed subsequent to the ninth
year varied irregularly in thickness. He stated that epidermal growth
took place at the margins of the laminae rather than over their entire
under-surfaces.
It is evident that the mode of scutular growth described by Carr
(_loc. cit._) applies to emyid turtles that shed the epidermal laminae
more or less regularly (for example, _Chrysemys_ and _Pseudemys_). In
these aquatic emyids a layer of the scute, the older portion,
periodically becomes loose and exfoliates usually in one thin,
micalike piece; since the loosened portion of the scute corresponds in
size to the scute below, it must be concluded that a layer of
epidermis is shed from the entire upper surface of the scute,
including the area of new epidermal growth. Box turtles ordinarily do
not shed the older parts of their scutes; the areola and successively
younger portions of the lamina remain attached to the shell until worn
off. The appearance of a single unworn scute, especially one of the
centrals or the posterior laterals, closely resembles a low, lopsided
pyramid.
Examination of parasagittal sections of scutes revealed that they were
composed of layers, the number of layers varying with the age of the
scute. A scute from a hatchling consists of one layer. A scute that
shows a single season of growth has two layers; a new layer is added
in each subsequent season of growth. Stratification is most evident in
the part of the scute that was formed in the first three or four
seasons and becomes increasingly less distinct in newer parts of the
scute. It may further be understood that scutes grow in the manner
described by Carr (_loc. cit._).
When the epidermal laminae are removed, a sheet of tough, pale grayish
tissue remains firmly attached to the bones of the shell beneath. This
layer probably includes, or consists of, germinal epithelium.
Contrasting pale and dark areas of the germinal layer correspond to
the pattern of markings on the scute removed.
[Illustration: FIG. 8. The second central scute from a juvenal
_T. o. ornata_ (KU 16133) in its third full season of growth.
A) Entire scute from above (à 2½); dashed line shows portion
removed in parasagittal section. B) Diagonal view of section
removed from scute in "A" (Ã 4-3/8, thickness greatly
exaggerated) showing layers of epidermis formed in successive
seasons of growth. Each layer ends at a major growth-ring
(M 1-3) that was formed during hibernation; minor growth-rings
(m), formed in the course of the growing season, do not result
from the formation of a new layer of epidermis. Note the
granular texture of the areola (a); the smooth zone between the
areola and M1 shows amount of growth in the season of
hatching.]
Growth of epidermal laminae is presumably stimulated by growth of the
bony shell. As the bone grows, the germinal layer of the epidermis
grows with it. When growth ceases at the beginning of hibernation, the
thin edges of the scutes are slightly down-turned where they enter the
interlaminal seams (Fig. 8). When growth is resumed in spring, the
germinal layer of the epidermis, rather than continuing to add to the
edge of the existing scute, forms an entirely new layer of epidermis.
The new layer is thin and indistinct under the oldest part of the
scute but becomes more distinct toward its periphery. Immediately
proximal to the edge of the scute, the new layer becomes greatly
thickened, and, where it passes under the edge, it bulges upward,
recurving the free edge of the scute above. At this time the formation
of a major growth-ring is completed. The newly-formed epidermis,
projecting from under the edges of the scute, is paler and softer than
the older parts of the scute; the presence or absence of areas of
newly formed epidermis enables one to determine quickly whether a
turtle is growing in the season in which it is captured. There is
little actual increase in thickness of the scute after the first three
or four years of growth. The epidermal laminae are therefore like low
pyramids only in appearance. This appearance of thickness is enhanced
by the contours of bony shell which correspond to the contours of the
scutes.
Minor growth-rings differ from major growth-rings in appearance and in
origin. Ewing (_op. cit._: 91) recognized the difference in appearance
and referred to minor growth-rings as "pseudoannual growth zones."
Minor growth-rings result from temporary cessations of growth that
occur in the course of the growing season, not at the onset of
hibernation. They are mere dips or depressions in the surface of the
scute. The occurrence of minor growth-rings indicates that
interruptions in growth of short duration do not result in the
formation of a new layer of epidermis. Slowing of growth or its
temporary cessation may be caused by injuries, periods of quiescence
due to dry, hot, or cold weather, lack of food, and possibly by
physiological stress, especially in females, in the season of
reproduction. Minor growth-rings that lie immediately proximal to
major growth-rings (Pl. 22, Fig. 2), are the result of temporary
dormancy in a period of cold weather at the end of a growing season,
followed by nearly normal activity in a warmer period before
winter-long hibernation is begun. Cagle (1946:699) stated that sliders
(_Pseudemys scripta elegans_) remaining several weeks in a pond that
had become barren of food would stop growing and develop a growth-ring
on the epidermal laminae; he did not indicate, however, whether these
growth-rings differ from those formed during hibernation.
In species that periodically shed scutes a zone of fracture develops
between the old and new layers of the scute as each new layer of
epidermis is formed, and the old layer is shed. Considering reptiles
as a group, skin shedding is of general occurrence; the process in
_Pseudemys_ and _Chrysemys_ differs in no basic respect from that in
most reptiles. Retention of scutes in terrestrial emyids and in
testudinids is one of many specializations for existence on land.
Retention of scutes protects the shell of terrestrial chelonians
against wear. Some box turtles were observed to have several scutes of
the carapace in the process of exfoliation but no exfoliation was
observed on the plastron. Exfoliation ordinarily occurred on the
scutes of the carapace that were the least worn; the exfoliating
portion included the areola and the three or four oldest (first
formed) layers of the scute. The layer of scute exposed was smooth and
had yellow markings that were only slightly less distinct than those
on the portion that was exfoliating.
Wear on the shell of a box turtle reduces the thickness of scutes, as
does the shedding of scutes in the aquatic emyids mentioned. It is
noteworthy that any of the layers in the scute of a box turtle can
form the cornified surface of the scute when the layers above it wear
away or are shed.
It is uncertain whether turtles that have ceased to grow at a
measurable rate continue to elaborate a new layer of epidermis at the
beginning of each season. Greatly worn shells of ornate box turtles,
particularly those of the subspecies _luteola_, have only a thin layer
of epidermis through which the bones of the shell and the sutures
between the bones are visible. I suspect that, in these old
individuals, the germinal layer of the epidermis does not become
active each year but retains the capacity to elaborate new epidermis
if the shell becomes worn thin enough to expose and endanger the bone
beneath it. The germinal layer of old turtles loses the capacity to
produce color.
Major growth-rings constitute a valuable and accurate history of
growth that can be studied at any time in the life of the turtle if
they have not been obliterated. They are accurate indicators of age
only as long as regular growth continues but may be used to study
early years of growth even in turtles that are no longer growing.
Minor growth-rings, if properly interpreted, provide additional
information on growing conditions in the course of each growing
season.
Nichols (1939a: 16-17) found that the number of growth-rings formed in
marked individuals of _T. carolina_ did not correspond to the number
of growing seasons elapsed; he concluded that growth-rings were
unreliable as indicators of age and that box turtles frequently
skipped seasons of growth. Woodbury and Hardy (1948:166-167) and
Miller (1955:114) came to approximately the same conclusion concerning
_Gopherus agassizi_. It is significant that these workers were
studying turtles of all sizes and ages, some of which were past the
age of regular, annual growth. Cagle's review of the literature
concerning growth-rings in turtles (1946) suggests that, in most of
the species studied, growth-rings are formed regularly in individuals
that have not attained sexual maturity but are formed irregularly
after puberty.
Cagle's (_op. cit._) careful studies of free-living populations of
_Pseudemys scripta_ showed that growth-rings, once formed, did not
change in size, that the area between any two major growth-rings
represented one season of growth, and that growth-rings were reliable
indicators of age as long as the impression of the areola remained on
the scutes studied. Cagle noted decreasing distinctness of
growth-rings after each molt.
The relative lengths of the abdominal lamina and the plastron remain
approximately the same throughout life in _T. ornata_. Measurements
were made of the plastron, carapace, and abdominal lamina in 103
specimens of _T. o. ornata_ from Kansas and neighboring states. The
series of specimens was divided into five nearly equal groups
according to length of carapace. Table 3 summarizes the relationship
of abdominal length to plastral length, and of carapace length to
plastral length. The mathematical mean of the ratio, abdominal
length/plastral length, in each of the four groups of larger-sized
turtles, was not significantly different from the same ratio in the
hatchling group. The relative lengths of carapace and plastron are not
so constant; the carapace is usually longer than the plastron in
hatchlings and juveniles, but shorter than the plastron in adults,
especially adult females.
TABLE 3.--The Relationship of Length of Abdominal Scute to
Plastral Length, and of Plastral Length to Length of Carapace,
in 103 Specimens of _T. o. ornata_ Arranged in Five Groups
According to Length of Carapace. The Relative Lengths of
Abdominal Scute and Plastron are not Significantly Different in
the Five Groups. The Plastron Tends to be Longer than the
Carapace in Specimens of Adult or Nearly Adult Size.
===============+=========+===========================+==================
| | Length of abdominal |Individuals having
| | as a percentage of | plastron longer
LENGTH | Number | length of plastron | than carapace
OF CARAPACE | of | |
|specimens|----------------+----------+------+-----------
| |Mean ±[sigma]m | Extremes |Number|Percentage
---------------+---------+----------------+----------+------+-----------
Less than | | | | |
50 mm. | 23 | 18.3±.498 |13.7-20.3 | 7 | 38.5
(Juveniles) | | | | |
---------------+---------+----------------+----------+------+-----------
50 to 69 mm. | 20 | 17.8±.303 |15.2-20.2 | 8 | 40.0
(Juveniles) | | | | |
---------------+---------+----------------+----------+------+-----------
70 to 100 mm. | 20 | 17.9±.445 |14.3-20.6 | 15 | 75.0
(Subadults) | | | | |
---------------+---------+----------------+----------+------+-----------
More than | | | | |
100 mm. | 20 | 17.8±.236 |16.4-20.6 | 13 | 65.0
(Adult males) | | | | |
---------------+---------+----------------+----------+------+-----------
More than | | | | |
100 mm. | 20 | 18.8±.510 |15.1-25.7 | 19 | 95.0
(Adult females)| | | | |
---------------+---------+----------------+----------+------+-----------
The length of any growth-ring on the abdominal lamina can be used to
determine the approximate length of the plastron at the time the
growth-ring was formed. Actual and relative increases in length of the
plastron can be determined in a like manner. For example, a
seven-year-old juvenile (KU 3283) with a plastron 74.0 millimeters
long had abdominal growth-rings (beginning with areola and ending with
the actual length of the abdominal) 5.9, 7.8, 9.5, 10.7, 12.0, 12.5,
14.3, and 14.9 millimeters long. Using the
[AB AB¹]
proportion, [-- = -- ], where AB is the abdominal length, PL the
[PL X ]
plastral length, AB¹ the length of any given growth-ring, and X the
plastral length at the time growth-ring AB¹ was formed, the plastral
length of this individual was 29.3 millimeters at hatching, 38.8 at
the end of the first full season of growth, and 47.2, 53.2, 59.6,
62.1, and 71.0 millimeters at the end of the first, second, third,
fourth, fifth, and sixth seasons of growth, respectively. The present
length of the abdominal (14.9 mm.) indicates an increment of three
millimeters in plastral length in the seventh season, up to the time
the turtle was killed (June 25). This method of studying growth in
turtles was first used by Sergeev (1937) and later more extensively
used by Cagle (1946 and 1948) in his researches on _Pseudemys
scripta_. Because the plastron is curved, no straight-line measurement
of it or its parts can express true length. Cagle (1946 and 1948)
minimized error by expressing plastral length as the sum of the
laminal (or growth-ring) lengths. This method was not possible in the
present study because growth-rings on parts of one or more laminae
(chiefly the gulars and anals) were usually obliterated by wear, even
in young specimens. It was necessary to express plastral length as the
sum of the lengths of forelobe and hind lobe.
The abdominal lamina was selected for study because of its length
(second longest lamina of plastron), greater symmetry, and flattened
form. Although the abdominal is probably subject to greater, over-all
wear than any other lamina of the shell, wear is even, not localized
as it is on the gulars and anals.
In instances where some of the growth-rings on an abdominal lamina
were worn but other rings remained distinct, reference to other, less
worn lamina permitted a correct interpretation of indistinct rings.
Abdominal laminae were measured at the interlaminal seam; since the
laminae frequently did not meet perfectly along the midline (and were
of unequal length), the right abdominal was measured in all specimens.
Growth-rings on the abdominal laminae were measured in the manner
shown in Plate 22.
Data were obtained for an aggregate of 1272 seasons of growth in 154
specimens (67 females, 48 males, and 39 of undetermined sex, chiefly
juveniles). Averages of calculated plastral length were computed in
each year of growth for specimens of known sex (Figs. 9 and 10) and
again for all specimens examined. Annual increment in plastral length
was expressed as a percentage of plastral length at the end of the
previous growing season (Fig. 11). Increment in plastral length for
the first season of growth was expressed as a percentage of original
plastral length because of variability of growth in the season of
hatching; growth increments in the season following hatching are,
therefore, not so great as indicated in Figure 11.
Growth of Juveniles
Areas of new laminal growth were discernible on laboratory hatchlings
soon after they ate regularly. Hatchlings that refused to eat or that
were experimentally starved did not grow. The first zone of epidermis
was separated from the areola by an indistinct growth-ring (resembling
a minor growth-ring) in most hatchlings, but in a few specimens the
new epidermis appeared to be a continuation of the areola. Major
growth-rings never formed before the onset of the first hibernation.
Growth in the season of hatching seems to depend on early hatching and
early emergence from the nest. Under favorable conditions hatchlings
would be able to feed and grow eight weeks or more before
hibernation. Hatchlings that emerge in late autumn or that remain in
the nest until spring are probably unable to find enough food to
sustain growth.
Sixty-four (42 per cent) of the 154 specimens examined showed
measurable growth in the season of hatching. The amount of increment
was determined in 36 specimens having a first growth-ring and an
areola that could be measured accurately. The average increment of
plastral length was 17.5 per cent (extremes, 1.8-66.0 per cent) of the
original plastral length. Ten individuals showed an increment of more
than 20 per cent; the majority of these individuals (8) were hatched
in the years 1947-50, inclusive.
[Illustration: FIG. 9. See legend for Fig. 10.]
[Illustration: FIG. 10. The relationship of size to age in
_T. o. ornata_, based on studies of growth-rings in 115
specimens of known sex (67 females and 48 males) from eastern
Kansas. Size is expressed as plastral length at the end of each
growing season (excluding the year of hatching) through the
twelfth and thirteenth years (for males and females,
respectively) of life. Vertical and horizontal lines represent,
respectively, the range and mean. Open and solid rectangles
represent one standard deviation and two standard errors of the
mean, respectively. Age is expressed in years.]
Some hatchlings that grow rapidly before the first winter are as large
as one- or two-year-old turtles, or even larger, by the following
summer. Individuals that grew rapidly in the season of hatching tended
also to grow more rapidly than usual in subsequent seasons; 80 per
cent of the individuals that increased in plastral length by 20 per
cent or more in the season of hatching, grew faster than average in
the two seasons following hatching. Early hatching and precocious
development presumably confer an advantage on the individual, since
turtles that grow rapidly are able better to compete with smaller
individuals of the same age. Theoretically, turtles growing more
rapidly than usual in the first two or three years of life, even if
they grew subsequently at an average rate, would attain adult size and
sexual maturity one or more years before other turtles of the same
age. A few turtles (chiefly males) attain adult size (and presumably
become sexually mature) by the end of the fifth full season of growth
(Figs. 9 and 10). These individuals, reaching adult size some three to
four years sooner than the average age, were precocious also in the
earlier stages of postnatal development.
Young box turtles reared in the laboratory grew more slowly than
turtles of comparable ages under natural conditions; this was
especially evident in hatchlings and one-year-old specimens. Slower
growth of captives was caused probably by the unnatural environment of
the laboratory. Captive juveniles showed a steady increase in weight
(average, .52 grams per ten days) as they grew whereas captive
hatchlings tended to lose weight whether they grew or not.
Growth in Later Life
After the first year growth is variable and size is of little value as
an indicator of age. Although in the turtles sampled variation in size
was great in those of the same age, average size was successively
greater in each year up to the twelfth and thirteenth years (for males
and females, respectively), after which the samples were too small to
consider mathematically.
Increments in plastral length averaged 68.1 per cent in the year after
hatching, 28.6 per cent in the second year and 18.1 per cent in the
third year. From the fourth to the fourteenth year the growth-rate
slowed gradually from 13.3 to about three per cent (Fig. 11). These
averages are based on all the specimens examined (with no distinction
as to sex); they give a general, over-all picture of growth rate but
do not reflect the changes that occur in growth rate at puberty (as
shown in Figs. 9 and 10).
Rate of growth and, ultimately, size are influenced by the attainment
of sexual maturity. Adult females grow larger than adult males. Males,
nevertheless, grow faster than females and become sexually mature when
smaller and younger. Examination of gonads showed 17 per cent of the
males to be mature at plastral lengths of 90 to 99 millimeters, 76 per
cent at 100 to 109 millimeters, and 100 per cent at 110 millimeters,
whereas the corresponding percentages of mature females in the same
size groups were: zero per cent, 47 per cent, and 66 per cent. Of the
females, 97 per cent were mature at 120 to 129 millimeters and all
were mature at 130 millimeters (Fig. 13). Because growth slows
perceptibly at sexual maturity, it is possible, by examination of
growth-rings, to estimate the age of puberty in mature specimens.
[Illustration: FIG. 11. Average increment in plastral length
(expressed as a percentage of plastral length at the end of the
previous season of growth) in the season of hatching (H) and in each
of the following 14 years of life, based on 1073 growth-rings. The
number of specimens examined for each year of growth is shown in
parentheses. Records for males and females are combined.]
Attainment of sexual maturity, in the population studied, was more
closely correlated with size than with age. For example, nearly all
males were mature when the plastron was 100 to 110 millimeters long,
regardless of the age at which this size was attained. The smallest
mature male had a plastral length of 99 millimeters; according to the
data presented in Figures 9 and 10, therefore, a few males reach
sexual maturity in the fourth year, and increasingly larger portions
of the population become mature in the fifth, sixth, and seventh
years. The majority become mature in the eighth and ninth years.
Likewise, females (smallest mature specimen, 107 mm.) may be sexually
mature at the end of the sixth year but most of them mature in the
tenth and eleventh years.
Annual Period of Growth
In growing individuals, narrow zones of new epidermis form on the
laminae in spring. Nearly all the growing individuals collected in May
of 1954 and 1955 had zones of new epidermis on the shell but those
collected in April did not. Activity in the first week or two after
spring emergence is sporadic and regular feeding may not begin until
early May. Once begun, growth is more or less continuous as long as
environmental conditions permit foraging. The formation of minor
growth-rings and adjacent growth-zones in autumn, provides evidence
that growth commonly continues up to the time of hibernation. The
number of growing days per year varies, of course, with the
favorableness of environmental conditions. The length of time (162
days) given by Fitch (1956b:438) as the average annual period of
activity for _T. ornata_ is a good estimate of the number of growing
days per season.
Environmental Factors Influencing Growth
Zones of epidermis formed in some years are wider or narrower than the
zones bordering them (Pl. 22). Zones notably narrower or wider than
the average, formed in certain years, constituted distinct landmarks
in the growth-histories of nearly all specimens; for example, turtles
of all ages grew faster than average in 1954 and zones of epidermis
formed in this year were always wider than those formed in 1953 and
1955.
An index to the relative success of growth in each calendar year was
derived. Records of growth for all specimens in each age group were
averaged; the figure obtained was used to represent "normal" or
average growth rate in each year of life (Fig. 12). The over-all
averages for the various age groups were then compared with records of
growth attained by individuals of corresponding age in each calendar
year, growth in a particular year being expressed as a percentage of
the over-all average. The percentages of average growth for all ages
in each calendar year were then averaged; the mean expressed the
departure from normal rate of growth for all turtles growing in a
particular calendar year. For example, the over-all average increment
in plastral length in the fifth year of life was 12.1 per cent, the
increment in the sixth year was 10 per cent, and so on (Fig. 11). In
1953, turtles in their fifth and sixth years increased in plastral
length by 11.4 and 9.1 per cent, or grew at 94.2 and 91.0 per cent of
the normal rate, respectively. The percentages of normal growth rate
for these age groups averaged with percentages of the other age groups
in 1953 revealed that turtles grew at approximately 86 per cent of the
normal rate in 1953.
Growth rates were computed for the twelve-year period, 1943-1954,
because of the concentration of records in these years. Scattered
records also were available for many of the years from 1901-1942.
Records for individuals in the season of hatching and the first full
season of growth were not considered.
Direct correlation exists between growth rate and average monthly
precipitation in the season of growth (April to September) (Fig. 12).
In nine of eleven years, the curve for growth rate followed the trend
of the curve for precipitation; but because other climatic conditions
also influenced growth, the fluctuations in the two curves were not
proportional to one another.
Grasshoppers form an important element in the diet of box turtles.
Smith (1954) traced the relative abundance of grasshoppers over a
period of 100 years in Kansas, and this information is of significance
for comparison with data concerning growth of box turtles. In general,
the growth index was higher when favorable weather and large
populations of grasshoppers occurred in the same year.
In the following summary, the numbers (1 to 5) used to express the
relative abundance of grasshoppers are from Smith (_op. cit._). Maxima
and minima refer to the twelve-year period, 1943-1954. The growth
index for each year (shown as a graph in Fig. 12) appears in brackets
and indicates the percentage of normal growth attained by all turtles
in that year.
_Years Favorable for Growth_
=1954= [126.3]: Growth was better than average for turtles of all
ages. Grasshopper populations were highest (4+) since 1948.
Continuously warm weather, beginning in the last few days of March,
permitted emergence in the first week of April; thereafter conditions
were more or less continuously favorable for activity until late
October. Although there was less than an inch of precipitation in
September, precipitation in August and October was approximately twice
normal and more or less evenly distributed. Warm weather in early
November permitted an additional two weeks of activity.
=1945= [125.5]: This was the second most favorable year for growth and
the second wettest year. Records of growth are all from young turtles
(one to four years old), all of which grew more than average. Daily
maximum temperatures higher than 60 degrees Fahrenheit on 18 of the
last 19 days of March, combined with twice the normal amount of
precipitation in the same period, stimulated early emergence. August
and October were both dry (each with less than one inch of
precipitation) but diurnal temperatures remained warm through the
first week in November and probably prolonged activity of box turtles
at least until then. Grasshoppers were more abundant (3.7) than
normal.
_Years Unfavorable for Growth_
=1944= [83.1]: This was the poorest growing year for the period
considered. The lack of a continuously warm, wet period in early
spring probably delayed emergence until the last week in April.
Temperatures remained warm enough for activity until early November,
but dry weather in September and October probably curtailed activity
for inducing long periods of quiescence; most of the precipitation
that occurred in the latter two months fell in a one-week period
beginning in the last few days of September. Grasshopper populations
were higher (4.0) than normal.
=1953= [85.6]: This was the second poorest growing year and the driest
year in the period considered. Intermittently cold weather in spring
delayed emergence until the last week in April when nearly an inch of
rain fell. Temperatures were higher than normal from June to October.
The period from September to the end of October was dry and the small
amount of precipitation that occurred was concentrated chiefly at the
beginning and end of that period. Temperatures in late October and
early November were lower than normal. Grasshopper populations were
low (2.2).
=1952= [88.3]: Environmental conditions were poor for growth and much
like the conditions described for 1953. In both years growth was much
less than normal in turtles of all ages except for one group (adults
that were 10 and 11 years old in 1952 and 1953, respectively) that was
slightly below normal in 1952 and slightly above normal in 1953.
The small number of records for 1955 were not considered in Figure
12. Warm weather in the last half of March lengthened the growing
season, and environmental conditions, as in 1954, were more or less
favorable throughout the rest of the summer; 1955 probably ranks with
1954 as an exceptionally good year for growth of box turtles.
Although the number of records available for turtles hatched in the
period from 1950 to 1954 is small, a few records are available for all
these years except 1951. In general, small samples of turtles hatched
in these years reflect only the difficulty of collecting hatchlings
and juveniles. In 1951, conditions for incubation and hatching were
poor and the lack of records for that year actually represents a high
rate of prenatal and postnatal mortality. Rainfall in the nesting
season was two to three times normal and temperatures were below
normal. Flooding occurred in low areas of Douglas County and many eggs
may have been destroyed when nests were inundated. Cold weather
probably increased the time of incubation for surviving eggs so that
only a few turtles could hatch before winter. Flooding and cold, wet
weather in the season of growth and reproduction, affecting primarily
eggs and hatchlings, may act as checks on populations of _T. ornata_
in certain years.
[Illustration: FIG. 12. The relation of growth rate in
_Terrapene o. ornata_ (solid line) to precipitation (dotted
line) in eastern Kansas. "Normal" rate of growth was determined
by averaging records of increase in length of plastron for
turtles in each age group. The growth index is expressed as a
percentage of normal growth and is the mean departure from
normal of all age groups in each calendar year. Precipitation
is for the period, April to September (inclusive), at Lawrence,
Douglas Co., Kansas. The means for precipitation (4.3) and
growth index (100) are indicated by horizontal lines at the
right of the graph.]
The environmental factors governing activity of terrestrial turtles
seem to differ at least in respect to threshold, from the factors
influencing the activity of aquatic turtles. A single month that was
drier or cooler than normal probably would not noticeably affect
growth and activity of aquatic emyids in northeast Kansas, but might
greatly curtail growth of box turtles.
Cagle (1948:202) found that growth of slider turtles (_Pseudemys
scripta_) in Illinois paralleled the growth of bass and bluegills in
the same lake; in the two years in which the fish grew rapidly, the
turtles did also, owing, he thought to "lessened total population
pressure" and "reduced competition for food." Growth of five-lined
skinks (_Eumeces fasciatus_) on the Natural History Reservation
paralleled growth of box turtles, probably because at least some of
the same environmental factors influence the growth of both species.
Calculations of departure from normal growth in _E. fasciatus_, made
by me from Fitch's graph (1954:84, Fig. 13), show that relative
success of growth in the period he considered can be ranked by year,
in descending order, as: 1951, 1949, 1948, 1950, 1952. This
corresponds closely to the sequence, 1951, 1948, 1949, 1950, 1952, for
_T. ornata_.
Number of Growing Years
Growth almost stops after the thirteenth year in females and after the
eleventh or twelfth year in males, approximately three years, on the
average, after sexual maturity is attained. The oldest individuals in
which plastral length had increased measurably in the season of
capture were females 14 (2 specimens) and 15 (1) years old. The age of
the oldest growing male was 13 years.
The germinal layer of the epidermis probably remains semiactive
throughout life but functions chiefly as a repair mechanism in adults
that are no longer growing. Growth-rings continue to form irregularly
in some older adults. Growth-rings formed after the period of regular
growth are so closely approximated that they are unmeasurable and
frequently indistinguishable to the unaided eye. If the continued
formation of growth-rings is not accompanied by wear at the edges of
the laminae, the laminae meeting at an interlaminal seam descend, like
steps, into the seam (Pl. 22, Fig. 2). Interlaminal seams of the
plastron deepen with advancing age in most individuals.
Some individuals that are well past the age of regular growth show
measurable increments in years when conditions are especially
favorable. The three oldest growing females were collected in 1954--an
exceptionally good year for growth. Allowing some latitude for
irregular periods of growth in favorable years subsequent to the
period of regular, more or less steady growth, 15 to 20 years is a
tenable estimate of the total growing period.
Longevity
Practically nothing is known about longevity in _T. ornata_ or in
other species of _Terrapene_ although the several plausible records of
ages of 80 to more than 100 years for _T. carolina_ (Oliver,
1955:295-6) would indicate that box turtles, as a group, are
long-lived. There is no known way to determine accurately the age of
an adult turtle after it has stopped growing. It was possible
occasionally to determine ages of 20 to 30 years with fair accuracy by
counting all growth-rings (including those crowded into the
interabdominal seam) of specimens having unworn shells. Without the
presence of newly formed epidermis as a landmark, however, it was
never certain how many years had passed since the last ring was
formed.
[Illustration: FIG. 13. The relationship of sexual maturity to
size in 164 specimens (94 females and 70 males) of _Terrapene
o. ornata_, expressed as the percentage of mature individuals
in each of five groups arranged according to plastral length.
Sexual maturity was determined by examination of gonads. Solid
bars are for males and open bars for females. The bar for males
in the largest group is based on assumption since no males in
the sample were so long as 130 mm. Males mature at a smaller
size and lesser age (see also Figs. 9 and 10) than females.
Plastral lengths of the smallest sexually mature male and
female in the sample were, respectively, 99 and 107 mm.]
Mattox (1936) studied annual rings in the long bones of painted
turtles (_Chrysemys picta_) and found fewer rings in younger than in
older individuals but, beyond this, reached no important conclusion.
In the present study, thin sections were ground from the humeri and
femurs of box turtles of various ages and sizes; the results of this
investigation were negative. Distinct rings were present in the
compact bony tissue but it appeared that, after the first year or two,
the rings were destroyed by encroachment of the marrow cavity at about
the same rate at which they were formed peripherally.
The only methods that I know of to determine successfully the
longevity of long-lived reptiles would be to keep individuals under
observation for long periods of time or to study populations of marked
individuals. Both methods have the obvious disadvantage of requiring
somewhat more than a human lifetime to carry them to completion.
Restudy, after one or more decades, of the populations of turtles
marked by Fitch and myself may provide valuable data on the average
and maximum age reached by _T. ornata_.
Ornate box turtles probably live at least twice as long as the total
period of growing years. An estimated longevity of 50 years would seem
to agree with present scant information on age. Considering
environmental hazards, it would be unusual for an individual to
survive as long as 100 years in the wild.
Weight
Weights of ornate box turtles varied so much that no attempt was made
to correlate weight with size. Absolute weights have little
significance since weight is affected to a large extent by the amount
of fluid in the body. Turtles that had recently imbibed were naturally
heavier than those that had not; turtles brought to the laboratory and
kept there for several days lost weight by evaporation and by voiding
water. Weights of 22 adult females (53 records) and 10 adult males (22
records) averaged 391 and 353 grams respectively, in the period from
September, 1954, to October, 1956. Females characteristically gained
weight in spring and early summer and were lighter after nesting.
Turtles of both sexes gained weight in September and October.
Bony Shell
_Fontanelles_
At the time of hatching, fontanelles remain where bones of the shell
have not yet articulated with their neighbors. In general, the
fontanelles of the shell are closed by the time sexual maturity is
attained, but some remain open a year or two longer.
The fontanelles of the shell are classified as follows (see Figs. 14
to 16 and 18 to 19):
_Plastron_
1.) _Anteromedian._ Rhomboidal; limited anteriorly by hyoplastral
bones and posteriorly by hypoplastral bones; posterior tip of
entoplastral bone may project into this fontanelle.
2.) _Posteromedian._ Limited anteriorly by hypoplastral bones and
posteriorly by xiphyplastral bones (since hypoplastral bones do not
articulate medially in hatchlings, anteromedian and posteromedian
fontanelles form a single, more or less dumbbell-shaped opening).
[Illustration: FIG. 14. Extent of closure of the
costoperipheral fontanelles in relation to length of plastron
in 17 skeletons of _T. o. ornata_ from eastern Kansas. Extent
of closure is expressed as an estimated percentage of total
closure of all the costoperipheral fontanelles, even though
some of them close sooner than others. Closure is usually
complete by the time sexual maturity is attained.]
_Carapace_
1.) _Costoperipheral._ Openings between the free ends of developing
ribs, between nuchal bone and first rib, and, between pygal bone and
last rib; limited laterally by peripheral bones; variable in shape.
2.) _Costoneural._ Triangular openings on either side of middorsal
line between proximal ends of costal plates and developing neural
plates.
The costoneural fontanelles are nearly closed in individuals of the 70
millimeter (plastron length) class and seldom remain open after a
length of 80 millimeters is attained (Fig. 14). Of the costoperipheral
fontanelles, the anterior one (between first rib and nuchal bone)
closes first and the posterior one (between last rib and pygal bone)
last. It remains open in some turtles in which the plastron is longer
than 100 millimeters. The remaining costoperipheral fontanelles close
in varying sequence but those in the area of the bridge (nos. 2 to 5),
where there is presumably greater stress on the shell, close sooner
than the others.
The plastral fontanelles are closed in most specimens of the 90
millimeter (plastron length) class; the anteromedian fontanelle closes
first.
The meager covering of the fontanelles makes juvenal turtles more
susceptible than adults to many kinds of injuries and to predation.
_Movable Parts of the Shell_
Parts of the shell that are more or less movable upon one another and
that function in closing the shell are found in several families of
Recent turtles. African side-necked terrapins of the genus _Pelusios_
have a movable forelobe on the plastron. Kinosternids have one or two
flexible transverse hinges on the plastron. In the Testudinidae the
African _Kinixys_ has a movable hinge on the posterior part of the
carapace and _Pyxis arachnoides_ of Madagascar has a short, hinged,
anterior plastral lobe. Certain trionychid turtles, such as
_Lissemys_, utilize the flexible flaps of the carapace (the flaps of
some species are reinforced with peripheral bones) to close the shell.
Movable shell-parts of turtles are, in general, protective in
function; they cover parts of the soft anatomy that would otherwise be
exposed.
A hinged plastron, capable of wholly or partly closing the shell,
occurs in six genera of the family Emyidae (see introduction). In
these emyids the plastron is divided into two lobes, which are joined
to each other by ligamentous tissue at the junction of the hyoplastral
and hypoplastral bones; externally, the hinge occurs along the seam
between the pectoral and abdominal laminae. This junction forms a more
or less freely movable hinge in adults. The plastron is attached to
the carapace by ligamentous tissue. Both lobes of the plastron or only
the buttresses of the hind lobe may articulate with the carapace. The
former condition obtains in _Emys_ and _Emydoidea_; the latter more
specialized condition is found in _Terrapene_.
In generalized emyid turtles such as _Clemmys_ there are no movable
shell parts. The plastron is joined to the carapace by the sutures of
the bridge. A long stout process, the axillary buttress, arises on
each side from the hyoplastron and articulates with the tip of the
first costal. A similar process, the inguinal buttress, arises from
the anterior part of each of the hypoplastral elements and meets the
sixth costal on each side. The buttresses form the anterior and
posterior margins of the bridge. It is clear that movement of the
plastron in many emyids is mechanically impossible because of the
bracing effect of the buttresses.
In _Terrapene_ the movable articulations of the shell are neither
structurally nor functionally developed in juveniles. Adults of _T.
ornata_ have highly modified bony buttresses on the plastron that are
homologous with those in more generalized emyids. The inguinal
buttresses are low and wide, and have a sheer lateral surface forming
a sliding articulation with the fifth and sixth peripheral bones of
the carapace. The axillary buttresses are reduced to mere bony points
near the posterolateral corners of the forelobe and do not articulate
directly with the carapace (Figs. 15 and 16).
The fifth peripheral bone, constituting the lowest point of the
carapace, has a medial projection that acts as a pivoting point for
both lobes of the plastron; the roughened anterior corners of the hind
lobe articulate with these processes. The roughened posterior corners
of the forelobe of the plastron likewise articulate with these
processes. The posterior process or "tail" of the entoplastron extends
to, or nearly to, the bony transverse hinge.
In juveniles that have been cleared and stained, the homologues of the
parts that are movable in adults are easily identifiable; the
proportions of these parts and their relations to one another are,
however, much different.
In juveniles (Figs. 18 and 19) the buttresses are relatively longer
and narrower, and are distinct--more nearly like those of generalized
emyids than those of adult _T. ornata_. The buttresses enclose a large
open space, which in adults is filled by the fifth peripheral. The
hyoplastral and hypoplastral bones are in contact only laterally. They
are firmly joined by bony processes; the interdigitating nature of
this articulation contrasts with its homologue in the adult, the point
where the roughened corners of the forelobes and hind lobes meet. The
fifth peripheral in juveniles (Fig. 19) lies dorsal to this
articulation. The position of the future transverse hinge corresponds
to a line passing through the articulations of the hyoplastra and
hypoplastra. The tail of the entoplastron ordinarily extends posterior
to this line in juveniles.
[Illustration: FIG. 15. Lateral view of adult shell (à ¾),
showing movable parts with anterior portion at left.
(Abbreviations are as follows: ab, axillary buttress;
hp, hypoplastron; hy, hyoplastron; ib, inguinal buttress;
p5, fifth peripheral bone; th, transverse hinge).]
[Illustration: FIG. 16. Medial view of adult shell (à ¾),
showing movable parts with anterior portion at left.
(Abbreviations as in fig. 15).]
[Illustration: FIG. 17. Lateral view of adult shell (à ¾),
showing scutellation of movable parts with anterior portion at
left. (Abbreviations are as follows: ap, apical scale; ax,
axillary scale; m5, fifth marginal scale; pl, pectoral
lamina.)]
The external scutellation of the plastral hinge in adults also differs
from that in juveniles. In adults (Fig. 17 and Pl. 8) the transverse
hinge is marked by ligamentous tissue between the pectoral and
abdominal laminae; the forelobe of the plastron is distinctly narrower
than the hind lobe. Two small scales lie near the corner of the hinge
on each side. The larger and more anterior of these scales is the
axillary; it is present in box turtles of all ages. The smaller scale
(Fig. 17), to my knowledge, has never been named or mentioned in the
literature; it is herein termed the apical scale. It is a constant
feature in adults but is always lacking in hatchlings and small
juveniles. Other scales, much smaller than the axillary and apical,
occur on the ligamentous tissue of the hinge of some adults.
[Illustration: FIG. 18. Plastron of hatchling (Ã 2), cleared
and stained to show bony structure. (Abbreviations not listed
in legend for Fig. 15 are as follows: af, anteromedian
fontanelle; ep, epiplastron; pf, posteromedian fontanelle.)]
[Illustration: FIG. 19. Carapace of hatchling (à 1½),
cleared and stained to show bony structure; lateral view;
anterior end at left. (Abbreviations as in Fig. 15.)]
[Illustration: FIG. 20. Lateral view of hatchling (Ã 1); note
the lateral process of the pectoral lamina (pl) extending
posterior to the axillary scale (ax) in a position
corresponding to the apical scale of adults. There is no
external indication of the transverse hinge in young
individuals. The yolk sac of this individual has been retracted
but the umbilicus (umb) has not yet closed.]
In juveniles (Fig. 20) the pectoroabdominal seam contains no
ligamentous tissue and is like the other interlaminal seams of the
plastron. A lateral apex of the pectoral lamina projects upward behind
the axillary scale on each side, in the position occupied by the
apical scale of adults. Examination of a large series of specimens
revealed that the apical scale of adults becomes separated from the
lateral apex of the pectoral lamina at approximately the time when the
hinge becomes functional as such.
Ontogenetic changes in the shell can be summarized as follows: 1)
Buttresses become less distinct in the first two years of life
(plastral lengths of 40 to 55 mm.); 2) Interdigitating processes of
the forelobes and hind lobes become relatively shorter and wider, the
entoplastron no longer projects posterior to the hinge, the lateral
apex of the pectoral lamina becomes creased, and some movement of the
plastron can take place between the second and third years (plastral
lengths of 55 to 65 mm.); 3) Plastral lobes become freely movable upon
one another and upon the carapace by the end of the fourth year
(plastral length approximately 70 mm.) in most individuals.
The plastron of a juvenal box turtle is not completely immovable. The
bones of the shell are flexible for a time after hatching and allow
some movement of the plastron; but the relatively greater bulk of the
body in young box turtles would prevent complete closure of the shell
even if a functional hinge were present. Hatchlings can withdraw the
head and forelegs only to a line running between the anterior edges of
the shell. To do so the rear half of the shell is opened and the hind
legs are extended. When the head and forelegs are retracted to the
maximum, the elbow-joints are pressed against the tympanic region or
behind the head; the fore-limbs cannot be drawn part way across the
snout, as in adults. Hatchlings can elevate the plastron to an angle
of approximately nine degrees; the plastron of an adult, with shell
closed, is elevated about 50 degrees. Hatchlings flex the plastron
chiefly in the region of the humeropectoral seam, rather than at the
anlage of the transverse hinge.
Adult box turtles, when walking, characteristically carry the forelobe
of the plastron slightly flexed. This flexion of the plastron,
combined with its naturally up-turned anterior edge, cause it to
function in the manner of a sled runner when the turtle is moving
forward. A movable plastron, therefore, in addition to its primarily
protective function, seems to aid the turtle in traveling through tall
grass or over uneven ground. The gular scutes, on the anterior edge of
the forelobe, become worn long before other plastral laminae do.
An adult female from Richland County, Illinois, had an abnormal but
functional hinge on the humeropectoral seam in addition to a normal
hinge on the pectoroabdominal seam. The abnormal hinge resulted from a
transverse break in which ligamentous tissue later developed. The
muscles closing the plastron moved the more anterior of the two
hinges; the normal hinge was not functional.
Color and Markings
The markings of the shell change first when postnatal growth begins
and again when sexual maturity is attained. They are modified
gradually thereafter as the shell becomes worn.
In hatchlings the ground color ordinarily is dark brown but in some
individuals is paler brown or tan. Markings on the dark background are
pale yellow. Markings on the central and lateral scutes vary from a
regularly arranged series of well defined spots and a middorsal stripe
to a general scattering of small flecks. In some specimens the pale
markings of the carapace are faint or wanting. Lateral parts of
marginal scutes are always pale yellow and form a border around the
carapace.
Close examination of the carapace of any hatchling shows the following
basic arrangement of markings: each lateral scute has a centrally
placed pale spot and four to seven smaller pale marks arranged around
the edge of the scute; each central scute has a central, longitudinal
mark and several (usually two, four, or six) smaller pale marks
arranged around the edge of the scute, chiefly the lateral edges (Pl.
23). Variations in pattern result when some or all of the markings
divide into two or more parts.
By the end of the first full season of growth, the markings have a
radial pattern. At this stage, the markings of the areola, with the
exception of the central spot, are obscure. The radial marks, sharply
defined and straight-sided, appear only on the newly formed parts of
the epidermal laminae. Each radial mark originates opposite one of the
peripheral marks of the areola. Other radial marks are developed later
by bifurcation of the original radiations.
The ground color of the plastron of hatchlings is cream-yellow, or
less often, bright yellow. The solid, dark brown markings on the
medial part of each lamina form a central dark area that contrasts
sharply with the pale background (Pl. 24). The soft tissue of the
navel is pale yellow or cream; when the navel closes, the dark
central mark of the plastron is unbroken except for thin, pale lines
along the interlaminal seams.
When growth begins, the areas of newly formed epidermal tissue on the
anterior and medial borders of each areolar scute are pale. Wide, dark
radial marks, usually three per scute, appear on the newly formed
tissue. Subsequently, finer dark radiations appear between the three
original radiations. The wide radiations later bifurcate. By the time
adult or subadult size is reached, the plastron appears to have a
pattern of pale radiations on a _dark_ background. In general, the
markings of the plastron are less sharply defined than the markings of
the carapace (Pl. 24).
There is a tendency for the dark markings of the plastron to encroach
on the lighter markings, if no wear on the shell occurs. However, as
the plastron becomes worn, the pale areas become more extensive and
the dark markings become broken and rounded. Severely worn plastra of
some old individuals lack dark markings. Wear on the carapace produces
the same general effect; but markings of the carapace, although they
may become blotched, are never obliterated in _Terrapene o. ornata_.
The top of the head in most hatchlings is dark brown, approximately
the same shade as the ground color of the carapace; the part anterior
to the eyes is usually unmarked but a few individuals have a
semicircle of small pale spots over each eye or similar spots on much
of the head. The posterior part of the head is ordinarily flecked with
yellow. The skin on the top of the head, particularly between the
eyes, is roughened. The granular skin of the neck is grayish brown to
cream-yellow. There are one or two large pale spots behind the eye and
another pale spot at the corner of the mouth. Smaller, irregularly
arranged pale markings on the necks of some specimens form, with the
post-orbital and post-rictal spots, one or two short, ragged stripes.
The gular region is pale.
In juveniles, the yellow markings of the head and neck are larger and
contrast more sharply with the dark ground color than in hatchlings.
Markings above the eyes, if present, fuse to form two pale,
semicircular stripes. In some older juveniles yellow marks on top of
the head blend with the dark background to produce an amber color. The
top of the neck darkens or develops blotches of darker color that
produce a mottled effect. Spots and stripes on the side of the neck
remain well defined. The skin on top of the head becomes smooth and
shiny.
Adult females tend to retain the color and pattern of juveniles on the
head and neck although slight general darkening occurs with age. Many
adult females have the top of the head marked with bright yellow
spots. In adult males, the top and sides of the head, anterior to the
tympanum, are uniformly grayish green or bluish green; the mandibular
and maxillary beaks are brighter, yellowish green. Markings on the
head and neck of most adult males are obscure (Pl. 25) but the sides
of the neck remain mottled in some individuals.
The antebrachium has large imbricated scales and _is_ distinctly set
off from the proximal part of the foreleg which is covered with
granular skin. The antebrachial scales of hatchlings are pale yellow;
each scale is bordered with darker color. General darkening of the
antebrachium occurs at puberty. In adult females each scale on the
anterior surface of the antebrachium is dark brown and has a
contrasting yellow, amber, or pale orange center. The anterior
antebrachial scales of adult males are dark brown to nearly black and
have bright orange or red centers. Old males have thickened
antebrachial scales.
The iris of hatchlings and juveniles is flecked with yellow and brown;
the blending of these colors makes the eye appear yellow, golden, or
light brown when viewed without magnification. Adult females retain
the juvenal coloration of the eye; the iris of adult males is bright
orange or red. The work of Evans (1952) on _T. carolina_ suggests that
eye color in box turtles is under hormonal control.
Wear
Presence or absence of areolae on laminae of the shell indicated
degree and sequence of wear. The anterior edges of carapace and
plastron, and the slightly elevated middorsal line (Pl. 23) wear
smooth in some individuals before the first period of hibernation.
Subsequent wear on the carapace proceeds posteriorly. For example,
turtles that retained the areola of the third central lamina, retained
also the areolae of the fourth and fifth centrals; when only one
central areola remained, it was the fifth. Lateral laminae wear in the
same general sequence. The areola of the fifth central lamina, because
of its protected position, persists in adult turtles that are well
past the age of regular growth. Areolae that are retained in some
older turtles are shed along with the epidermal layers formed in the
first year or two of life. Wear on the shell is probably correlated
with the habits of the individual turtle; smoothly-worn specimens
varied in size and age but were usually larger, older individuals. No
smoothly worn individual was still growing.
Wear on the plastron is more evenly distributed than wear on the
carapace; wear is greatest on the lowest points of the plastron (the
gular laminae, the anterior portions of the anal laminae, and the
lateral edge of the tranverse hinge).
The claws and the horny covering of the jaws are subject to greater
wear than any other part of the epidermis; presumably they continue to
grow throughout life. The occasional examples of hypertrophied beaks
and claws that were observed, chiefly in juveniles, were thought to
result from a continuous diet of soft food or prolonged activity on a
soft substrate. Ditmars (1934:44, Fig. 41) illustrated a specimen of
_T. carolina_, with hypertrophied maxillary beak and abnormally
elongate claws, that had been kept in a house for 27 years.
The conformation of the maxillary beak in all species of _Terrapene_
is influenced to a large extent by wear and is of limited value as a
taxonomic character. The beak of _T. ornata_ is slightly notched in
most individuals at the time of hatching and remains so throughout
life. The underlying premaxillary bone is always notched or
bicuspidate. The sides of the beak are more heavily developed than the
relatively thin central part. Normal wear on the beak maintains the
notch (or deepens it) in the form of an inverted U or V, much in the
manner of the bicrenate cutting edge on the grooved incisors of
certain rodents. In a series of 34 specimens of _T. ornata_ from
Kansas, selected at random from the K. U. collections, 92 per cent had
beaks that were "notched" to varying degrees, four per cent had hooked
(unnotched) beaks, and four per cent had beaks that were flat at the
tip (neither hooked nor notched).
[Illustration: FIG. 21. Plantar views of right hind foot (male
at left, female at right) of _T. o. ornata_ (Ã 1), showing
sexual dimorphism in the shape and position of the first toe.
The widened, thickened, and inturned terminal phalanx on the
first toe of the male is used to grasp the female before and
during coitus.]
SEXUAL DIMORPHISM
Differences between adult males and females of _T. ornata_ have been
mentioned in several places in the preceding discussion of growth and
development. Several sexual characteristics--greater preanal length,
thickened base of the tail, slightly concave plastron, and smaller
bulk--are found also in males of many other kinds of emyid turtles.
From females, males of _T. ornata_ are most easily distinguished by
the bright colors of their eyes, heads, and antebrachial scales. An
additional, distinctive characteristic of males is the highly modified
hind foot. The first toe is greatly thickened and widened; when the
foot is extended, the first toe is held in a horizontal plane nearly
at right angles to the medial edge of the plantar surface (Fig. 21).
The hind foot of females is unmodified in this respect. Males tend to
have heavier, more muscular hind legs than females.
The bright colors of males are maintained throughout the year and do
not become more intense in the breeding season. Males of _T. o.
luteola_ become melanistic in old age whereas males of the subspecies
_ornata_ do not. In old males of _luteola_ the skin becomes dark gray,
bluish, or nearly black and much of the bright orange or red of the
antebrachial scales and the green of the head is obliterated; the iris
may also darken but in most specimens it retains some red. Females of
_luteola_ tend also to darken somewhat in old age but not so much as
males; females of _ornata_ do not. Table 4 summarizes the more
important secondary sexual characters of _T. ornata_.
TABLE 4.--A Summary of Sexual Dimorphism in _Terrapene ornata_.
============+============================+==============================
CHARACTER | MALES | FEMALES
------------+----------------------------+------------------------------
Head | Snout truncate in lateral | Snout relatively round in
| profile, top of head and | lateral profile; front of
| front of maxilliary beak | maxillary beak not forming
| forming an angle of nearly | right angle with top of head;
| 90°; head yellowish green | head dark brown, distinct
| to bluish green; markings | pale markings on head and
| on head and neck reduced; | neck; head commonly spotted
| head never spotted dorsally| dorsally (Pl. 25, Figs. 5
| (Pl. 11, Figs. 7 and 8). | and 6).
------------+----------------------------+------------------------------
Iris | Red | Yellowish brown
------------+----------------------------+------------------------------
Hind legs | Heavy and muscular; first | Not especially heavy or
| toe turned in, thickened, | muscular; first toe, if
| and widened (Fig. 21). | turned in, never thickened
| | or widened (Fig. 21).
------------+----------------------------+-----------------------------
Forelegs | Centers of antebrachial | Centers of antebrachial
| scales bright orange or | scales yellow, pale orange,
| red. | or brown.
------------+----------------------------+-----------------------------
Carapace | Relatively lower, length | Relatively higher, length
| contained in height (48 | contained in height (94
| specimens) .58 times | specimens) .50 times
| (± .005[sigma]m, range, | (± .005[sigma]m,
| .50 to .69). | range .44 to .60).
------------+----------------------------+------------------------------
Plastron | Ordinarily slightly | Flat or convex, never
(hind lobe)| concave. | concave.
------------+----------------------------+------------------------------
TEMPERATURE RELATIONSHIPS
Tolerances to environmental temperatures, and reactions to thermal
stimuli influence the behavior of ectothermal animals to a large
extent. _Terrapene ornata_, like other terrestrial reptiles
inhabitating open grassland, is especially subject to the vicissitudes
of environmental temperature. Other species of turtles living in the
same area are more nearly aquatic and therefore live in a microhabitat
that is more stable as regards temperature.
Approximately 500 temperature readings in the field and many others in
the laboratory were obtained from enough individuals to permit
interpretation of reactions involved in basking, in seeking cover, and
in emerging from temporary periods of quiescence at various times of
the day.
Box turtles commonly used open places such as cow paths, ravines, and
wallows, for basking as well as for feeding and as routes of travel.
Burrows, dens beneath rocks, and forms, were used as shelter from high
and low temperatures as well as from predators. Determining whether a
turtle was truly active (moving about freely, feeding, or copulating),
was basking, or was seeking shelter was difficult because the turtle
sometimes reacted to the observer; for instance, basking turtles,
whose body temperatures were still suboptimum, might take cover when
surprised, and truly active turtles might remain motionless and appear
to be basking. By scanning open areas from a distance with binoculars,
an observer frequently could determine what turtles were doing without
disturbing them. In the final analysis of data, temperature records
accompanied by data insufficient to determine correctly the state of
activity of the turtle, were discarded, as were temperature records of
injured turtles and turtles in livetraps.
Cowles and Bogert (1944:275-276) and Woodbury and Hardy (1948:177)
emphasized the influence of soil temperatures on body temperatures. It
is thought that air temperatures played a more important role than
soil temperatures in influencing body temperatures of _T. ornata_.
Soil temperatures were taken in the present study only when the turtle
was in a form, hibernaculum, or den.
Optimum Temperature
Cowles and Bogert (1944:277) determined optimum levels of body
temperature of desert reptiles by averaging body temperatures falling
within the range of normal activity; they defined this range as, "...
extending from the resumption of ordinary routine [activity] ... to
... a point just below the level at which high temperatures drive the
animal to shelter." Fitch (1956b:439) considered optimum body
temperature in the several species that he studied to be near the
temperature recorded most frequently for "active" individuals; he
found (_loc. cit._) that of body temperatures of 55 active _T.
ornata_, 66 per cent were between 24 and 30 degrees, and that the
temperatures 27 and 28 occurred most frequently. Fitch concluded (_op.
cit._:473) that the probable optimum body temperature of _T. ornata_
was 28 degrees and that temperatures from 24 to 30 degrees were
preferred. Although Fitch treated all non-torpid individuals that were
abroad in daytime as "active" and did not consider the phenomenon of
basking, his observations on optimum body temperature agree closely
with my own.
Body temperatures of 153 box turtles that were known definitely to be
active, ranged from 15.3 to 35.3 degrees. The mean body temperature
for active turtles was 28.8 degrees (± 3.78[sigma]) (Fig. 22).
Ninety-two per cent of the temperatures were between 24 and 30 degrees
and 50 per cent were between 28 and 32; temperatures of 29 and 30
degrees occurred most frequently (22 and 21 times, respectively). The
ten body temperatures below 24 degrees all were recorded before 9 A.
M. on overcast days when the air was cool and humid. It is noteworthy
that two of these low temperatures (18.8° and 19.0°) were from a
copulating pair of turtles; two others (21.8° and 22.0°) were from
individuals that were eating. The highest temperature (35.3°) was from
a large female that was feeding at mid-morning in a partly shaded
area.
The mean body temperature for active individuals (Fig. 22) is probably
somewhat below the ecological optimum, because a few temperatures were
abnormally low. The large number of body temperatures in the range of
29 to 31 degrees indicates an optimum closer to 30 degrees. Optimum
body temperatures may vary somewhat with the size, sex, or individual
preference of the turtle concerned.
Basking
Although basking is common in terrestrial turtles, only a few authors
have mentioned it. Woodbury and Hardy (1948:177-178) did not use the
term in their account of thermal relationships in _Gopherus agassizi_;
their discussion indicates, however, that the tortoises move
alternately from sunny to shady areas to regulate body temperature.
Desert tortoises removed from hibernacula and placed in the sun warmed
to approximately 29.5 degrees before they became active, although a
few did so at temperatures as low as 15 degrees. According to Cagle
(1950:45), Sergeev (1939) studied body temperature and activity in the
Asiatic tortoise, _Testudo horsefieldi_, and found that individuals
basked for as much as two hours in the morning before beginning the
first activity of the day (feeding), but that tortoises did not bask
after a period of quiescense from late morning to late afternoon,
during which body temperatures were seemingly maintained nearer the
optimum than they were during nocturnal rest; body temperatures rose
to approximately 30 degrees before the tortoises became active. Since
body temperatures of 23 to 24 degrees were maintained at night, the
basking range of _Testudo horsefieldi_ may be considered to be
approximately 23 to 32 degrees.
Ornate box turtles basked chiefly between sunrise and 10 or 11 A. M.
Body temperatures of 60 basking turtles ranged from 17.3 to 31.4
degrees (mean, 25.5 ± 3.08[sigma]). More than two-thirds (42) of these
body temperatures were higher than the air temperature near the
turtle, indicating probably that body temperature rises rapidly once
basking is begun. In the instances where body temperature was below
air temperature, the turtles had recently begun to bask (many were
known to have just emerged from forms or other cover where they had
spent the night) or were warming up more slowly because of reduced
sunlight. On cloudy days basking began later than on clear days and
body temperatures usually remained at a suboptimum level. Turtles that
basked on days that were cloudy and windy, or cold and windy, did so
in sheltered places, usually on the leeward sides of windbreaks such
as limestone rocks, rock fences, or ravine banks. It was evident in
these instances that the turtles either sought such shelter from the
wind or remained ensconced in the more complete shelter of a form or
burrow, not emerging at all.
Open areas of various kinds were used as basking sites. Level
ground--such as on roads, cattle pathways, and bare areas surrounding
farm ponds--having unobstructed morning sunlight, nearby dense
vegetation, and choice opportunities for feeding (cow dung, mulberry
trees) was preferred. Basking was frequently combined with feeding; in
several instances box turtles were noted early in the morning at
suboptimum body temperatures eating grasshoppers, berries, or dung
insects. The predilection of box turtles for open areas is probably
important in permitting extended activity at suboptimum temperatures.
_T. ornata_ probably carries on more nearly normal activity on cool
days than do reptilian species with more sharply delimited thermal
tolerances. Collared lizards (_Crotaphytus collaris_), for example,
are chiefly inactive on days when the sky is overcast, although a few
individuals having suboptimum body temperatures can be found in open
situations (Fitch, 1956a:229 and 1956b:442).
[Illustration: FIG. 22. The relationship of body temperature
(Centigrade) and kind of activity in _T. o. ornata_, compiled
from 355 field observations. Vertical and horizontal lines
represent, respectively, the range and mean. Open and solid
rectangles represent one standard deviation and two standard
errors of the mean, respectively.]
Toleration of Thermal Maxima and Minima
The foregoing remarks on basking indicate the approximate, normal,
thermal tolerances of ornate box turtles. Many additional records of
body temperature were taken from turtles that were found under cover.
Turtles under cover in daylight were usually seeking protection from
either below-optimum or above-optimum temperatures. In avoiding low
temperatures, turtles usually chose more complete and permanent cover
than in avoiding high temperatures.
Body temperatures of 64 box turtles that were seeking cover or that
were under cover because of high temperatures ranged from 28.9 to 35.8
degrees (mean, 31.9 ± 1.55[sigma]). Fifty-nine of these temperatures
(92 per cent) were 30 degrees or higher. Figure 22 shows this range to
overlap broadly with the temperature range of active turtles and the
means of the two groups are close to each other. Body temperatures
below 30 degrees (5) were all recorded late in the morning on hot
summer days when the air temperature was well above 30 degrees; they
are somewhat misleading because they are from turtles that were under
cover long enough to lower body temperature to the range of activity
although the turtles remained under cover because of hazardous
environmental temperatures.
The commonest retreats used by box turtles to escape heat were burrows
of other animals and small dens under thick limestone rocks, where the
air remained cool, even in late afternoon. Most of the burrows and
dens on the Damm Farm were known to me and could be checked each day.
Turtles seeking temporary refuge from high temperatures
characteristically rested just inside the opening of a den or burrow.
Less frequently, turtles burrowed into ravine banks or just under the
sod on level ground. A number of individuals with above-optimum body
temperatures were found in the shade of trees or high weeds in early
afternoon on hot days. Mulberry trees provided ample shade for such
activity and, in June and July, when ripe mulberries were abundant on
the ground, turtles frequently fed on them at times of the day when
temperatures were more hazardous in other areas.
Several turtles were found buried in mud or immersed in water at the
edges of ponds in the hottest part of the day; they were discovered at
first by accident and, on subsequent field trips by systematic
probing. Ordinarily the turtles were covered with mud or muddy water
and remained motionless, except for periodically raising the head to
the surface to breath. There was little vegetation near the edges of
ponds and by late morning on hot days the temperature of the
shallowest water was as high as the air temperature or higher.
Correspondingly, turtles found resting in mud and water had body
temperatures much higher than turtles in dens, burrows, or forms at
the same time of day. Box turtles that retreat to mud or shallow water
cool themselves less efficiently than they would in drier, better
protected microhabitats. I found no evidence that turtles went into
deeper water to cool themselves.
The length of time spent under cover varied; most turtles had two
daily periods of activity, the second beginning in late afternoon.
Some turtles moved from shelter to shelter in the time between periods
of activity. Several turtles were known to remain quiescent
continuously for several days in the hottest part of the summer.
The maximum temperature that a reptile can tolerate physiologically is
ordinarily higher than the maximum temperature tolerated voluntarily
(Cowles and Bogert, 1944:277); but, the two maxima may be separated by
only a few degrees. Most poikilothormous vertebrates neither tolerate
nor long survive body temperatures exceeding 40 degrees (Cowles and
Bogert, _op. cit._:269).
It is evident (Fig. 22) that ornate box turtles do not often tolerate
body temperatures above 33 degrees and that temperatures in excess of
35 degrees are probably never tolerated under natural conditions. At
9:15 A. M. on July 5, 1955, an adult female emerged from mud where she
had spent the night (body temperature 28.4°, mud 28.4°, air 30°).
After foraging for 40 minutes in bright sunlight on a grassy hillside
she had moved approximately 100 feet and her temperature had reached
34.6 degrees (air 33.0°). At 9:56 A. M. she moved rapidly and directly
to a den under a rock nearby; 15 minutes later her body temperature
had not changed but after 65 minutes it had dropped to 33.4 degrees.
The temperature of air in the den was 31 degrees. This female began
her activities at nearly optimum body temperature relatively late in
the morning and, by foraging intensively for less than one hour,
probably was able nearly to satisfy her daily food requirements; by
foraging near suitable cover she could remain active until her body
temperature reached a critical threshold, and she thereby saved time
otherwise required for finding cover or making a form.
The following observations, extracted from field notes, indicate that
body temperatures near 40 degrees are the approximate lethal maximum
and are well above those temperatures voluntarily tolerated by _T.
ornata_. On July 4, 1955, a subadult female was in the water at the
edge of a pond. The temperatures of the air, water, and turtle were
32.0, 30.6, and 30.2 degrees, respectively. At 11 A. M. the turtle was
tethered in direct sunlight on the hard-baked clay of the pond
embankment (temperature of air 33.4°). The turtle's response to
steadily rising body temperature over a period of 31 minutes is
illustrated by the following notes.
Body
Time (A. M.) temperature Remarks
11:00 33.0 Tethered on slope.
11:05 34.6 Strains at tether in several directions.
11:09 36.5 Tries frantically to get away; draws in limbs and
head rapidly and momentarily at any movement on
my part, and hisses loudly.
11:13 37.5 Mouth held open slightly; turtle overturns in effort
to escape; frantic scrambling resumed a few seconds
after I right turtle.
11:17 38.2 Mouth now held open most of the time; white
froth begins to appear around mouth.
11:20 38.6 Stops activities every 10 seconds or so, rests chin
on ground and gapes widely; will still pull into
shell when prodded with stick.
11:23 39.2 Still wildly active; continues to gape widely every
few seconds.
11:27 39.4 Frothing at mouth profusely.
11:30 39.6 Attempts to escape are now in short feeble bursts.
11:31 Turtle released; crawls toward me and immediately
seeks shade of my body; when I move off, turtle
seeks shade of small isolated weed on pond embankment;
turtle removed to damp earth at edge
of pond.
11:35 39.5 Attempts to burrow into mud at edge of pond.
11:36 Enters shallow water and moves slowly back to
shore.
11:37 38.8 Turtle thrown into center of pond where it remains
motionless and drifts with wind to opposite
shore; remains inactive in mud and shallow water
at edge of pond; temperature of water near turtle
35.5.
11:57 35.0 Moves 50 ft. up slope to shade of low vegetation.
01:55 P. M. 32.5 Turtle has not moved.
The overheating may have incapacitated the turtle since it moved only
50 feet in the next two days; its body temperatures on the two days
subsequent to the experiment were 26.8 and 20.6, respectively.
The mentioned gaping, as in higher vertebrates generally, cools the
animal by evaporation from the moist surfaces of the mouth and
pharynx. By keeping the mouth open for more than a few minutes at a
time in hot dry weather, a turtle would surely lose body water in
amounts that could not always be easily replaced. Ornate box turtles
seem to utilize evaporation for cooling only in emergencies and rely
for the most part on radiation and conduction to lower body
temperature after reaching a relatively cool, dark retreat.
Box turtles were never active at body temperatures below 15 degrees
and were seldom active at temperatures below 24 degrees. The two
lowest temperatures (15.3° and 16.3°) were taken from individuals
crossing roads on overcast days in early May.
In 78 box turtles that were under cover because their environmental
temperatures were low, the body temperatures ranged from 2.7 to 30.6
degrees (mean 19.8 ± 6.38[sigma]). The range of body temperatures in
this group is greater than in the other groups shown in Figure 22
because low body temperatures were studied over a wide range of
conditions, including hibernation.
Box turtles actually seek cover because of low temperatures only in
fall and spring and on occasional unseasonable days in summer when
temperatures drop rapidly. Retreat to cover, in the normal cycle of
daily activity, is governed usually by high temperatures at mid-day or
by darkness at the end of the day. Turtles in dens, burrows, and grass
forms, tended to burrow if temperatures remained low for more than a
few hours.
Box turtles under cover where they cannot bask have little control
over the lower range of body temperatures. The freezing temperatures
of winter can be escaped by burrowing deeper into the ground.
Temperatures approaching the lethal minimum, however, seldom occur
during the season of normal activity. By remaining hidden in a burrow
or den therefore, box turtles are fairly well protected from predators
but are at a thermal disadvantage.
A number of turtles that had wet mud on their shells were found
basking in early morning near ditches, ponds, and marshy areas;
several others were partly buried in mud, shortly after daybreak, and
another was at the edge of a pond after dark.
Eight adults, located just as they emerged from cover in early morning
on sunny days, had body temperatures of 19.7, 21.9, 24.2, 24.5, 25.8,
26.6, 28.7, and 29.5 degrees. In five emerging from earth forms, body
temperatures were at least a degree or two below the temperature of
the air; the other three came from mud or shallow water and had body
temperatures higher than the air temperature.
Temperature is probably the primary stimulus governing emergence after
temporary periods of quiescence. Turtles in earthen forms are usually
completely covered or are head downward with only the hind quarters
exposed. Obviously, the more thoroughly a turtle protects itself
(beneath the insulating cover of a form, burrow, or den) against
unfavorable temperatures, the longer it will take for favorable
temperatures to bring about normal activity again. Turtles in forms
and deep burrows have a minimum of contact with the outer environment;
but in dens beneath rocks and in shallow burrows light and air can
enter freely. Turtles might be influenced in their activities to some
extent by the intensity of light at the opening of a burrow or den;
they are surely stimulated by changes in the temperature and humidity
of air coming through the opening. Shallow retreats that a turtle can
enter and leave with the least effort therefore seem most efficient
for purposes of thermocontrol, especially when they provide earthen
surfaces into which the turtles can burrow more deeply if more severe
environmental conditions develop.
In October, 1955, nine _T. ornata_ of various sizes, collected in
Douglas County, Kansas, were brought to the laboratory for observation
under conditions of controlled temperature. They were kept at room
temperature for several days and were fed regularly, with the
exception of one hatchling that was fed nothing in this period. On
October 22 the turtles were placed in a room where the temperature was
maintained constantly at zero degrees. One of the nine turtles, an
adult female, was killed with chloroform immediately prior to its
removal to the cold room. A list of the turtles used in this
experiment is given below.
Age Carapace Weight
class length in mm. in grams
1) Hatchling 33.1 8.4
2) Hatchling[A] 29.9 6.7
3) Juvenile 52.5 29.3
4) Juvenile 50.2 26.1
5) Adult [Male] 125 376
6) Adult [Female] 118 400
7) Adult [Male] 119 386
8) Adult [Female] 110 325
9) Adult [Female] 115 ----
[A] Starved.
Turtles were kept in the cold room for periods of 100 minutes
(hatchlings and juveniles) and 200 minutes (adults). The entire
experiment, including the time in which the turtles were allowed to
warm after they were taken from the cold room, covered a period of
nearly six hours (375 minutes) during which the turtles were under
constant observation. Individual body temperatures were taken
continuously in this period (39 for each juvenile and 24 for each
adult) in the order that the turtles were numbered; gaps between
records of the body temperature of a given individual therefore
represent the time required to record temperatures for the rest of the
turtles in the group. The rates of rise and fall of temperature for
each of the nine turtles considered are shown as a graph in Figure 23.
Rate of temperature change was inversely proportional to bulk;
hatchlings, for example, cooled and warmed a little more than twice as
rapidly as did adults. Rate of temperature change was intermediate in
juveniles but was more nearly like that of adults in the warming phase
and closer to that of hatchlings in the cooling phase (Table 5).
Considering that hatchling no. 2 was smaller than no. 1, the rate of
change in its temperature did not seem to be significantly altered by
starvation. The adult males showed a tendency to change temperature
faster than adult females even though both males were larger than any
of the females. The slight difference in rate of temperature change
between the sexes (Fig. 23) may have been fortuitous.
One hatchling (No. 1), when its temperature dropped below one degree,
fully extended all four limbs and the body was elevated and only the
anterior edge of the plastron was in contact with the confining glass
dish. Raising the body from an uncomfortably cold or hot substrate is
a well known phenomenon in many lizards and in crocodilians, but to my
knowledge has not been reported for turtles.
TABLE 5.--Average Rate of Change in Temperature (Expressed in Degrees
per minute) for four Groups of Turtles Subjected to Temperature
of Zero Degrees and then Allowed to Warm at 27 Degrees
(Centigrade).
==================+========+=========+=============
| | Cooling | Warming
GROUP | Number | phase | phase
| | | (to 25°)
------------------+--------+---------+-------------
Hatchlings | 2 | .282 | .310
| | |
Juveniles | 2 | .264 | .180
| | |
Adult [Male] | 2 | .122 | .152
| | |
Adult [Female] | 3 | .119 | .130[B]
| | |
Adult (all) | 5 | .120 | .138
------------------+--------+---------+-------------
[B] None of the females reached a temperature of 25° before
the experiment was terminated.
[Illustration: FIG. 23. Changes in temperature of the body of
four juvenal (nos. 1 to 4) and five adult individuals of
_T. o. ornata_ (nos. 5 to 9) exposed to a constant air
temperature of zero degrees Centigrade for periods of 100 and
200 minutes, respectively. The vertical arrows indicate when
the turtles were removed to an air temperature of 27 degrees.
Sizes and weights of the turtles used are given in the text.
Turtle number nine, a female, was killed by means of chloroform
before experiment began. Rate of change in temperature in
specimens was inversely proportional to size. All turtles
survived the experiment.]
Hibernating turtles and those experimentally chilled were usually
comatose but were almost never completely incapacitated even at
temperatures at or near zero degrees. Experimental pinching, probing,
and pulling revealed that muscles operating the neck, the limbs, and
the lobes of the plastron could be controlled by the turtle at low
temperatures; hissing, resulting from rapid expulsion of air through
the mouth and nostrils (when the head and limbs are drawn in
reflexively) occurred at all body temperatures but was sometimes
barely audible in the coldest turtles. Of all living turtles observed,
only two (hatchlings 1 and 2 in coldroom experiment) were completely
immobile at low temperatures, failing to respond even to pinpricks at
body temperatures of 0.8 and 1.7 degrees, respectively, although other
turtles, under the same experimental conditions, consistently gave at
least some response to the same stimulation.
Turtles chilled experimentally continued to move about voluntarily,
albeit sluggishly, at temperatures much lower (2.5° for each of four
adults; 10.0° and 6.2° for two juveniles) than those at which
locomotion was resumed in the warming phase (13° for the adults, 21.7°
and 20.1° for the juveniles). Hatchlings chilled so rapidly that it
was difficult to ascertain accurately the temperature at which
inactivity was induced. Juveniles became active gradually, moving
slowly about when the body temperature reached approximately 20
degrees but not attempting more strenuous activities such as climbing
the walls of enclosures, until body temperatures of 22 to 25 degrees
were attained. Adults, on the other hand, exhibited "normal" activity
as soon as they became voluntarily active.
The ability of ornate box turtles to move about when the body
temperature is near the lethal minimum probably enables those caught
in the open by a sudden drop in environmental temperature to find
cover that keeps them from freezing to death. Prolonged chilling, on
the other hand, seems to create a physiologically different situation;
the temperature at which activity is resumed is higher and subject to
less variation.
Juveniles were more rapidly affected by environmental temperatures,
were subject to different thresholds, and were inactive over a wider
range than were the adults. Indeed, the _rate_ of chilling, rather
than absolute body temperature alone, might in large measure influence
the reactions of turtles to environmental temperatures. If this be so,
smaller turtles, having a narrower thermal range of normal activity,
must lose at least some of the advantages gained by their ability to
warm up more rapidly.
Hatchlings and juveniles at the Damm Farm were always active on days
when at least some adults were also active. Fitch (1956b:466) found
that, in northeastern Kansas, species of small reptiles and amphibians
are active earlier in the season than larger species and that the
young of certain species become active earlier than adults. Fitch
stated, "... small size confers a distinct advantage in permitting
rapid rise in body temperature by contact with warmed soil, rock or
air, until the threshold of activity is attained"; he pointed out also
that young animals, if able to emerge earlier than adults, would
benefit from a longer growing season. Hatchlings and juveniles of _T.
ornata_ would benefit greatly from an extra period of activity of say,
one or two weeks in spring and a similar period in autumn, especially
if food were plentiful. The extra growth realized from such a "bonus"
period of feeding would significantly increase the chance of the
individual turtle to survive in the following season of growth and
activity.
Ornate box turtles are active within a narrower range of temperatures
than are aquatic turtles in nearby ponds and streams of the same
region. Observations by William R. Brecheisen and myself on winter
activity of aquatic turtles indicate that, in Anderson County, Kansas,
the commoner species (_Chelydra serpentina_, _Chrysemys picta_, and
_Pseudemys scripta_) are more or less active throughout the year;
although they usually do not eat in winter, they are able to swim
about slowly and in some instances (_P. scripta_) even to carry on
sexual activity at body temperatures only one or two degrees above
freezing. But, ornate box turtles hibernating in the ground a few
yards away are incapable of purposeful movement at such low body
temperatures.
HIBERNATION
In northeastern Kansas ornate box turtles are dormant from late
October to mid-April--approximately five and one half months of the
year. Individuals may be intermittently active for short periods at
the beginning and end of the season, however. Once a permanent
hibernaculum is selected dormancy continues until spring; unseasonably
warm weather between mid-November and March does not stimulate
temporary emergence. There is little movement during dormancy except
for the deepening or horizontal extension of the hibernaculum.
Woodbury and Hardy (1948:171) found desert tortoises (_Gopherus
agassizi_) in dormancy from mid-October to mid-April in southwestern
Utah; some tortoises became temporarily active on warm days in winter.
Cahn (1937:102) was able to compare hibernation in several individuals
each of _T. ornata_ and _T. carolina_, kept under the same conditions
in Illinois. Individuals of _T. ornata_ burrowed into the ground in
October, two weeks before those of _T. carolina_ did, and continued to
burrow to a maximum depth of 22½ inches. Some individuals of _T.
carolina_ spent the entire winter in the mud bottom of a puddle and
became semiactive on warm winter days. Other individuals of _T.
carolina_ burrowed nearly as deeply as did _T. ornata_. Individuals of
_T. ornata_ emerged from hibernation one or two weeks later in the
spring than did those of _T. carolina_. There are some indications
that populations of _T. carolina_ in eastern Kansas are dormant for a
shorter period of time than those of _T. ornata_ but comparative
studies are needed to verify this. Richard B. Loomis gave me a large
female of _T. carolina_ that he found active beside a highway in
Johnson County, Kansas, on November 23, 1954; on that date most
individuals of _T. ornata_ under my observation had already begun
permanent hibernation but a few at the Reservation were still
semiactive.
Fitch (1956b:438) listed earliest and latest dates on which box
turtles were active at the Reservation in the years 1950 to 1954; in
the five year period box turtles were active an average of 162 days
per year (range, 140-187) or approximately 5.3 months of the year. It
is significant that 1954, having the most days of activity was,
according to my studies of growth-rings, an exceptionally good year
for growth. Fitch's data indicate the approximate season of growth and
reproduction but not of total activity, since he did not take into
account the sporadic movements of box turtles in late fall and early
spring.
Activity in autumn is characterized by movement into ravines and low
areas; many turtles move into wooded strips along the edges of fields
or small streams. Sites protected from wind, providing places for
basking and for burrowing, are sought. Burrows of other animals, along
the banks of ravines, were often used for temporary shelter;
overhanging sod at the lips of ravine-banks provided cover beneath
which turtles could easily burrow. After mid-October progressively
fewer box turtles were found in open places and activity was
restricted to a few hours in the warmest part of the day.
Low air temperature probably is the primary stimulus for hibernation.
Autumn rains are usually followed by a decrease in general activity.
Rain probably hastens burrowing by softening the ground.
Ornate box turtles more often than not excavate their own hibernacula.
Digging begins with the excavation of a shallow form which is deepened
or extended horizontally over a period of days or weeks. Such
hibernacula are sometimes begun at the edges of rocks or logs; the
overhanging edge of an unyielding object acts as a fulcrum on the
shell and hastens digging. Ornate box turtles are slow but efficient
burrowers.
Forms in open grassy areas are begun at an angle of 30 to 40 degrees;
an adult box turtle requires approximately one hour to burrow far
enough beneath the sod to conceal itself but can dig into soft, bare
earth much more rapidly. Once a hibernaculum is begun, all four feet
are used for its excavation, the front feet doing most of the digging
and the hind feet pushing loose earth to the rear.
Several turtles were seen entering burrows and dens in late autumn and
trailing records showed that some individuals visited several of these
shelters in the course of a single day.
By means of systematic probing of known hibernacula it was found that
they are deepened gradually in the course of the winter. Depth seems
to be governed by the temperature of the soil. Hibernacula in wooded
or sheltered areas were ordinarily shallower than hibernacula in open
grassland.
In the autumn of 1953-54 two pens were constructed at the Reservation
in order to study hibernation; one pen was on a wooded hillside and
the other was on open grassland. Turtles in the grassland pen were in
newly excavated hibernacula, just beneath the sod, on October 25 and
did not emerge for the remainder of the winter, whereas turtles in the
woodland pen were intermittently active until November 10.
Correspondingly, turtles in the grassland pen descended to depths of
eight and one half and 11½ inches, respectively, whereas those in
the woodland pen were covered by a scant six inches of loose earth and
leaf litter. In 1954 four turtles were traced (by means of trailing
threads) to hibernacula on wooded slopes at the Reservation; two
entered permanent hibernacula on November 13 and two remained
semiactive until sometime after November 20. All four turtles spent
the winter in hibernacula that were not more than six inches deep.
Temperatures of the soil at a depth of nine inches were usually
slightly lower at the grassland pen than at the woodland pen on a
given date. It is probably significant that individuals with trailing
devices and individuals in experimental pens furnish the latest
records for autumn activity. The unnatural conditions created by
confining the turtles in pens restricted the number of hibernation
sites that were available to them; although trailing devices did not
affect the normal movements of box turtles on the surface of the
ground these devices certainly hampered the turtles somewhat in
digging. However, it is noteworthy that box turtles are able to move
about after mid-November, whether this is of general occurrence under
more natural conditions or not. Depths of hibernacula at the Damm Farm
were also influenced by amount of vegetation or other cover. Maximum
depth of hibernacula in more or less open situations ranged from seven
to 18 inches whereas a female hibernating in a ditch that was covered
with a thick mat of dead grasses was four inches beneath the surface
of the soil, and another female was only two and one half inches below
the floor of a den.
Several _T. ornata_ kept by William R. Brecheisen in a soil-filled
stock tank on his farm in the winter of 1955-56, burrowed to maximum
depths of seven to eight inches in the course of the winter. A layer
of straw covered the soil. All the turtles were alive the following
spring except for one juvenile, found frozen at a depth of one inch on
December 30 (the lowest air temperature up to this time was
approximately -12°). Three adult and 24 juvenal _T. ornata_
hibernating in the earth of an outdoor cage at the University of
Kansas in the winter of 1955-56, were all dead on December 3 after air
temperatures had reached a low of -12 degrees.
Ornate box turtles are usually solitary when hibernating; in the rare
instances in which more than one turtle is found in the same
hibernaculum, the association has no social significance and is simply
a reflection of the availability and suitability of the hibernaculum.
The only communal hibernaculum--the "Tree Den"--at the Damm Farm was
discovered on October 16, 1955, after a turtle was traced to it by
means of a trailing thread. The flask-shaped cavity, approximately two
and one-half feet deep, in the north-facing bank of a narrow ravine,
had an entrance one foot wide and nine inches high, nearly flush with
the bottom of the ravine. Grasses on the bank of the ravine hung over
the entrance and nearly concealed it. The steep sides of the ravine
protected the entrance from wind.
Seven turtles were in the den when it was discovered, and on each of
five subsequent visits from October 20, 1955, to March 6, 1956, fewer
turtles were found in the den. Figure 24 shows the approximate length
of stay of each known occupant of the den. Only one of the turtles
(an adult female) that left the den returned. Turtles found in the den
on three visits in October were more or less torpid and were seen
easily from the entrance but on November 6 the two remaining
individuals had burrowed into the sides and floor of the den.
Three turtles (one female, one male, and one juvenile) were found in
separate form-hibernacula within a few inches of one another on
November 6, 1955 (Pl. 21, Fig. 2). The common entrance to all three
hibernacula was a shallow depression that resulted from an old
post-hole. Soil in the depression was loose and moist and ideal for
burrowing. The three hibernating turtles were situated, in a vertical
plane, at depths of 18 ([Male]), 12 (juvenile), and seven ([Female])
inches. One of the turtles hibernating at this place on November 6 was
basking on October 30 in the shelter of some tall weeds a few feet
from the hibernaculum.
[Illustration: FIG. 24. The approximate length of stay of each
known occupant of a den that was examined six times in the
winter of 1955-1956 at the Damm Farm. Most of the occupants
used the den as a temporary shelter and sought permanent
hibernacula elsewhere. One turtle left the den for
approximately two weeks and then returned to it for the rest
of the winter. The temperature of the air outside the den (A)
and the average body temperature of turtles in the den (B) are
given at the bottom of the diagram for each date the den was
examined. The symbol "J" represents a juvenal turtle.]
In general, body temperatures approximated the temperature of the soil
around the turtle. Body temperatures tended to be slightly higher than
soil temperatures in November and December but were slightly lower
than soil temperatures in the months of February and March. The lowest
body temperature recorded for any turtle that survived a winter was
2.7 degrees, taken from an adult female on December 26, 1955. Body
temperatures one to three degrees higher were common in the coldest
part of the winter. Turtles in shallow hibernacula, like those
observed in wooded areas at the Reservation, are probably subjected to
freezing temperatures at least for short periods but I have no records
of body temperatures this low, except where they were induced
experimentally. Turtles exposed to temperatures of zero degrees or
slightly lower would retain enough heat to survive without freezing
for a period of several hours or even a day if well insulated. A
temperature gradient exists within the body; cloacal temperatures, for
example, differ from temperatures deep in the colon and temperatures
in the dorsal and ventral parts of the body cavity (taken by
manipulating the bulb of the thermometer while it was in the colon)
differ from one another. Probably, therefore, some parts of some
turtles--probably the top of the shell or the extremities--freeze in
winter without causing the death of the turtle. Ewing (1939:91) found
a female of _T. carolina_, just emerging from hibernation, that had
lost some scutes from its carapace; he found the missing scutes in the
hibernaculum and attributed their loss to severe temperatures in the
winter of 1933-34.
The incidence of mortality due to freezing is unknown for most species
of reptiles. The observations of Bailey (1948) on DeKay snakes
(_Storeria dekayi_) and Legler and Fitch (1957) on collared lizards
suggest that rates of mortality are high in dormant reptiles. Bailey
(_op. cit._) suggested that winter mortality might act as a natural
check on snake populations. Neill (1948a:114) thought more box turtles
(_T. carolina_) were killed in Georgia by cold weather in late autumn
than "... by all other factors together," and that this winter
mortality acted as an effective check on population levels. Neill
reported that many turtles left their burrows in late autumn and began
to forage; if the temperature dropped suddenly, the turtles became
"... too torpid to dig" and froze.
If ornate box turtles are occasionally caught in the open by a sudden
cooling of air temperature, it would occur at a time of year when
temperatures would approximate freezing but would drop not far below
this level; laboratory and field records show that adults could
probably survive these low temperatures overnight and warm up
sufficiently on the following day to seek adequate shelter. Box
turtles deepening their burrows in winter do so at body temperatures
somewhat lower than 10 degrees (near the minimum temperature at which
co-ordinated activity was observed in the laboratory); turtles found
in the open in late October were known to burrow into the ground at
body temperatures of approximately 15 degrees.
Emergence from hibernation usually occurs in April but in some years a
few turtles may emerge as early as the first week of March. Emergence
is stimulated by temperature and humidity. Fitch (1956b:438) stated
that emergence was delayed until "... the ground has been sufficiently
moistened and until air temperatures have reached at least 26°." Box
turtles at the Reservation emerged on April 21 in 1954 and from April
16 to 17 in 1955. William R. Brecheisen found recently emerged box
turtles in Anderson County on April 2, 1955, and March 6, 1956.
Turtles were found facing upward in their hibernacula in early March.
As the temperature of the soil rises, they move slowly upward, usually
following the route by which they entered. They remain just below the
surface of the soil for a week or two before actually emerging; this
final phase of emergence is probably hastened by spring rains that
soften the soil. Activity may be sporadic after emergence if the
weather is cold.
A number of box turtles at the Reservation emerged in a cold rain in
1954 when the temperatures of the air and ground were 16 and 13
degrees, respectively, but remained inactive for several days
afterward. In 1955 the air and ground temperatures were higher (28°
and 17°, respectively) on the day of emergence and box turtles became
active almost immediately.
DIET
Published information on the food of _T. ornata_ consists of a few
miscellaneous observations. Cahn (1937:103) opened five stomachs that
contained partly digested vegetable matter but no insects or other
animal food: Ortenburger and Freeman (1930:187) noted that
grasshoppers were a main part of the diet of _T. ornata_ in Oklahoma
and that turtles displayed unsuspected agility in catching them. Those
authors also saw turtles eating caterpillars and robber flies.
Strecker (1908:79) stated that "The natural diet of this species
consists of vegetable matter and earthworms." Norris and Zweifel
(1950:3) observed the feeding habits of captive _T. o. luteola_.
Coyote melon (_Cucurbita foetidissima_) was eaten with reluctance but
a collared lizard (_Crotaphytus collaris_) was quickly devoured.
Tadpoles of _Scaphiopus hammondi_ were caught in a small pool and
eaten. Adults of the same species were rejected after being caught;
box turtles were seen wiping their mouths after rejecting adult toads.
The authors suggested that _T. o. luteola_ is an important predator of
_Scaphiopus hammondi_, since the two species occur together in many
areas and the emergence of both is controlled to a large extent by
rainfall. One individual of _luteola_ was seen eating a dead box
turtle on a road.
Captive individuals of _T. ornata_, observed in the present study, ate
nearly every kind of animal and vegetable food given to them. Table
scraps, consisting chiefly of greens, various fruits and vegetables,
meat, and cooked potatoes, formed the main diet of turtles kept in
outdoor cages.
A number of persons have told me of ornate box turtles eating the
succulent stems and leaves, and the fruits of various garden plants;
similar incidents probably occur in areas of native vegetation. J.
Knox Jones told me he saw an individual of _T. ornata_ eating a
spiderwort (_Tradescantia_ sp.) in Cherry County, Nebraska.
Sight-records of foods eaten by box turtles at the Damm Farm
(excluding the many records of individuals foraging in dung or eating
mulberries) were for grasshoppers, caterpillars, and various kinds of
carrion. Box turtles were often seen eating grasshoppers on roads in
early morning; Sophia Damm told me of frequently seeing individuals
catching grasshoppers in her garden. Ralph J. Donahue told me that on
his farm in Bates County, Missouri, an individual of _T. ornata_ made
a circuit of the lawn each morning in summer and ate all the cicadas
(_Magicicada septendecim_) found.
Vertebrate remains found in the stomachs of box turtles seem to result
chiefly from the ingestion of carrion. One box turtle ate a white egg
(unidentified) that had fallen from a nest and another was seen with a
blue down feather clinging to its mouth. Several colleagues have told
me of box turtles eating small mammals caught in snap-traps and Marr
(1944:489) reported a similar incident. J. Knox Jones told me he once
found an ornate box turtle in the nest of a blue-winged teal in Cherry
County, Nebraska; the three eggs in the nest had been broken. The only
authentic record of an ornate box turtle preying on a vertebrate under
natural conditions was one supplied by Ralph J. Donahue who saw an
adult catch and eat one of a brood of bobwhite quail. In many areas
where box turtles are abundant, it is the opinion of local residents
that the turtles decimate populations of upland game birds by eating
the eggs and young of these birds; these opinions result probably from
rare encounters such as the one described by Donahue. I believe that
box turtles at the Damm Farm were sometimes able to catch young frogs
and tadpoles (chiefly _Rana catesbeiana_ and _R. pipiens_) at the
margins of ponds. In autumn literally thousands of young _Rana_ were
present in these places.
Ornate box turtles ordinarily attempt to catch and, without further
examination, to eat, small objects moving on the ground, but are more
critical of stationary objects. Captive turtles, for example, would
immediately chase and seize a grape that was pulled or rolled slowly
across a floor but a stationary grape was examined and then smelled
before it was eaten. Similar observations were made a number of times
with living and dead insects in the field and in the laboratory. A
turtle discovering an object that is of possible value as food,
approaches it closely, turns the head from side to side (presumably
using the eyes alternately to examine the object), and then, with head
cocked at a slight angle, momentarily presses the nostrils against the
object (Pl. 28, Fig. 4). If acceptable as food, the object is then
swallowed whole or taken into the mouth with a series of bites; large
insects are usually broken into several pieces in the process of being
bitten and swallowed. Larger objects, such as dead vertebrates, are
torn to pieces with the beak and forefeet before they are swallowed.
Hatchlings, when fed for the first time, ignored inanimate foods but
eagerly chased mealworms, catching them usually by the anterior end.
The tendency of the young of certain species of turtles (especially
captives) to be more carnivorous than adults is probably due to the
association of movement with food; recognition of inanimate objects as
food is presumably learned by older individuals.
Mulberries (_Morus rubra_), when they are abundant, constitute all or
an important part of the diet of ornate box turtles. On June 4, 1955,
William R. Brecheisen and I drove along a road in Anderson County,
Kansas, and stopped at each mulberry tree that we saw beside the road;
we found at least one specimen of _T. ornata_ under nearly every tree.
Approximately twenty box turtles were collected in this manner in a
little more than one hour. The heads and necks of most were stained
dark-red from the fruit and, in some, nearly the entire shell was
stained. Dissection of these turtles revealed that their stomachs were
distended to two or three times normal size with mulberries; no other
kinds of food were found in the stomachs. Some of the turtles voided
purplish-black fluid from the cloaca when we handled them; the color
of the fluid presumably resulted from mulberries.
Several turtles were observed through binoculars as they foraged.
Individuals snapped or lunged periodically at objects on the ground
along the route of travel. Upon reaching an area where cow dung was
abundant, a turtle would move directly to a pile of dung and begin
tearing it apart with the forelegs or burrowing into it. Turtles most
often foraged in cow dung that had a superficial, dried crust. The
invertebrate fauna of older dung was probably greater than that of
fresh dung. Adult and larval insects were eaten, along with quantities
of dung, as they were uncovered. Sometimes box turtles chased and
caught larger insects that ran a foot or more away from the pile of
dung; the turtles could cover the distance of one foot with three or
four quick steps. Depressions made by box turtles in cow dung, as well
as drier cow dung that had been more completely dissected, were
regarded as characteristic "sign" of _T. ornata_ at the Damm Farm and
in other areas studied (Pl. 26). Several persons have told me of box
turtles "eating cow dung"; these reports, most of them made by
competent observers, probably result from observations of box turtles
ingesting cow dung incidentally, along with some unseen item of food.
Contents of stomachs were analyzed. Scats and contents of lower
digestive tracts, although obtained in large quantity, were unsuitable
for analysis because of the fragmentary nature of the foods they
contained. Relative amounts of various kinds of foods in stomachs were
estimated; volume was determined by displacement of water or fine
shot.
Twenty-three stomachs of adults were selected at random (except for
the fact that empty stomachs were discarded) from more than a hundred
specimens collected in Douglas County, Kansas, in the period from
June, 1954, to June, 1957; the sample included stomachs obtained in
nearly all the months of the season of activity. Kinds of foods in
stomachs did not differ significantly in regard to the sex of the
turtles or to time of year. The stomach of each of two juveniles
(included in Table 6) contained a greater variety of animal food than
did the stomach of any adult, but no kind of animal was eaten by the
juveniles exclusively.
Each of the 23 stomachs contained animal matter and, in addition, all
but two contained at least some plant material from dung, which
constituted up to 20 per cent of total stomach contents.
Insects were present in each of the 23 stomachs and constituted the
bulk of the animal matter; beetles, caterpillars, and grasshoppers
(ranked in descending order) were the kinds occurring most frequently
and constituting the largest average percentages of total
stomach-contents. Most of the beetles were scarabaeids and carabids;
the bulk of the caterpillars were noctuids and arctiids. Grasshoppers,
with one exception, were of a single species, _Melanoplus
differentialis_. It is noteworthy that two of the kinds of insects
frequently eaten (differential grasshoppers and noctuid caterpillars)
are of economic importance in that they damage crops.
TABLE 6.--Kinds of Animals Found in the Stomachs of 25 _Terrapene o.
ornata_ of Both Sexes (23 adults, 2 juveniles) from Douglas
County, Kansas. Frequency of Occurrence (number of stomachs in
which found) is Given for Each Item Listed.
=======================================+=============================
| FREQUENCY OF OCCURRENCE
|--------+-----------+--------
| Adults | Larvae | Total
---------------------------------------+--------+-----------+--------
Gastropoda | | |
_Helisoma_ sp | 1 | | 1
_Succinia_ sp | 1 | | 1
_Polygyra_ sp | 1 | | 1
_Retinella_ sp | 1 | | 1
---------------------------------------+--------+-----------+--------
Crustacea | | |
_Procambaris gracilis_ | 1 | | 1
_Armadillidium vulgare_ | 4 | | 4
---------------------------------------+--------+-----------+--------
Orthoptera (Locustidae) | | |
Locustinae (_Melanoplus | | |
differentialis_) | 13 | | 13
Oedipodinae | 1 | | 1
| | |
Lepidoptera (unspecified) | | 1 | 1
Arctiidae | | 9 | 9
Noctuidae | | 10 | 10
Pyralidae | | 1 | 1
Sphingidae | | 1 | 1
| | |
Diptera (Sarcophagidae) | | 1 | 1
| | |
Coleoptera (unspecified) | 3 | | 3
Cantharidae | | 1 | 1
Carabidae (unspecified) | 6 | | 6
(_Eumolops colossus_) | 1 | | 1
Cerambycidae (_Prionus fissicornis_) | 1 | | 1
Chrysomelidae | | |
(_Diabotrica 12-punctata_) | 1 | | 1
Curculionidae (_Calendra parvulus_) | 3 | | 3
Lampyridae (_Photinus pyralis_) | 2 | | 2
(_Photuris sp._) | | 1 | 1
Phengodidae | | 1 | 1
Scarabaeidae | 11 | | 11
| | |
Hymenoptera (Formicidae) | 2 | | 2
---------------------------------------+--------+-----------+---------
Phalangida | 1 | | 1
| | |
Araneida (_Epeira_) | 1 | | 1
| | |
Diplopoda | 1 | | 1
---------------------------------------+--------+-----------+---------
Vertebrata (carrion) | | | 4
---------------------------------------+--------+-----------+---------
TABLE 7.--Occurrence of Insects, by Frequency and Volume, in Stomachs
of 23 _Terrapene ornata_ from Douglas County, Kansas. Relative
Volume is Based on Total Amount of Food Material Present, Excluding
Stones and Vegetable Material Contained in Dung.
===================+=========+=============+==============+==========
| Insects | Orthoptera | Lepidoptera |Coleoptera
| (all) | | (larvae) |
-------------------+---------+-------------+--------------+----------
Average | | | |
volumetric | | | |
percentage | 88.6 | 28.7 | 26.9 | 32.5
-------------------+---------+-------------+--------------+----------
Range | | | |
(volumetric | trace | | |
percentage) | to 100 | 0 to 100 | 0 to 100 | 0 to 100
-------------------+---------+-------------+--------------+----------
Frequency of | | | |
occurrence | | | |
(percentage | 100 | 52 | 65 | 74
of total stomachs | | | |
in which found) | | | |
-------------------+---------+-------------+--------------+----------
Snails, sowbugs, and the one individual of crayfish found in stomachs
were kinds that could be expected to occur in moist grassland or in
wooded stream courses. Mulberries were present in one stomach and
fragments of bird's-nest fungi (_Cyathus striatus_) were present in
another. Carrion consisted of remains of mammals and birds; the only
identifiable items were bones of the eastern cottontail (_Sylvilagus
floridanus_) and a chicken. Stones up to seven millimeters in diameter
were found in many stomachs; stones constituted as much as half of
total stomach-contents. Presumably the stones were accidentally
swallowed when food was taken from the ground.
The few adequate reports on dietary habits of _T. carolina_ (Allard,
1935:325-326; Carr, 1952:147, 150, 152, 153; Stickel, 1950:361;
Surface, 1908:175-177) indicate that the species is omnivorous but
that individuals tend to be herbivorous or carnivorous at certain
times. Ornate box turtles resemble _T. carolina_ in being
opportunistic feeders but rely on insects as a staple part of the
diet. In this respect the ornate box turtle seems to differ from all
other kinds of box turtles in the United States and it is probably
unique in its habitual utilization of dung communities as a source of
food.
POPULATIONS
Ornate box turtles were probably more numerous on the Damm Farm than
any other kinds of reptiles, excepting skinks (_Eumeces fasciatus_ and
_E. obsoletus_), and were by far the most conspicuous element of the
reptilian fauna.
The 194 box turtles that were marked at the Damm Farm were captured a
total of 437 times. Seventy-nine (41 per cent) individuals were
recaptured at least once, 49 (25 per cent) twice, 29 (15 per cent)
three times, and 20 (10 per cent) were recaptured at least four times.
Only three individuals were recaptured more than eight times. The
greatest number of recaptures for a single individual, an old female,
was 23.
In all, 185 turtles (95 per cent of total recorded at Damm Farm) were
captured on the pasture. Of these, 73 were in the northwest corner
area, 44 in the house pond area, and 35 in the southern ravine area.
The density of the population at the Damm Farm, considering the entire
area, was .88 turtles per acre; for the woodland area alone, density
was .41 turtles per acre and for the pasture alone, density was 1.49.
Acreage and population density in the northwest corner, house pond,
and southern ravine areas were respectively, 28 acres with 2.6 turtles
per acre, 7 acres with 6.3 turtles per acre, and, 17 acres with 2.6
turtles per acre. The densities noted above for the wooded area and
for the entire Damm Farm are low as a result of incomplete sampling in
the wooded area. Estimates of population density for the subdivisions
of the pasture seem more closely to approach the true population
density in areas of favorable habitat.
Fewer unmarked turtles were captured as the study progressed, but they
were still being captured occasionally when field work was terminated.
In order to estimate the number of turtles in the population at the
Damm Farm the "Lincoln Index" (Lincoln, 1930) was used to compare the
ratio of marked individuals to total number of individuals (17:56) in
collections for June, 1956, to the ratio of marked individuals as of
July 31, 1955 (87) to total individuals in the population; the result
was 286.
Fitch (1958:78) estimated the population of _T. ornata_ in one area of
the Reservation (including woodland and ungrazed pasture) to be .076
turtles per acre. Stickel (1950:373) estimated the population of adult
_T. carolina_ to be four to five turtles per acre in favorable habitat
at the Patuxent Research Refuge, Laurel, Maryland; juveniles comprised
less than ten per cent of the population.
Of the 194 turtles marked at the Damm Farm, 103 (53 per cent) were
adult or subadult females, 61 (31 per cent) were mature males, and 30
(16 per cent) were juveniles of undetermined sex. The ratio of males
to females was then, 1.00 to 1.69, and the ratio of juveniles to
adults was, 1.00 to 6.47. Eighteen of the 194 individuals were
juveniles less than 90 millimeters in plastral length and only six had
plastra less than 60 millimeters long (Fig. 25). The unbalanced ratio
between males and females may result, in part, from sexual differences
in habits. The studies of Carr (1952:9), Fitch (1954:140), Forbes
(1940:132), Legler (1954:138), and Risley (1933:690), have shown,
however, that unbalanced sex ratios, with females outnumbering males,
are found in several species of reptiles, especially in turtles.
Records for 540 adult _T. ornata_ collected at the Damm Farm, the
Reservation, and on roads in eastern Kansas, show that females
outnumber males just before and during the nesting season and again in
late autumn (Fig. 26). The high incidence of females in May, June, and
July, can be explained by their more extensive movements associated
with nesting in these months. I have no explanation for the increased
number of females captured in late autumn. In April and August, the
only two months in which males were more abundant than females, the
samples were small. The number of juveniles collected was too small to
allow any trustworthy conclusions concerning their seasonal incidence;
a few juveniles were taken in nearly all the periods in which adults
were active.
Risley (1933:690), studying _Sternotherus odoratus_ in Michigan, found
an over-all sex ratio of 1.0 male to 2.3 females; the percentage of
females in collections ranged from 50 to 71 per cent in April and most
of May and rose to 83 and 85 per cent in late May and mid-June,
respectively.
The infrequency with which hatchlings and small juveniles of ornate
box turtles are observed is well known to naturalists. Several of my
colleagues who are expert field observers and who have lived in areas
where ornate box turtles are abundant, have never seen hatchlings;
many other persons have seen only one or two. Rodeck (1949:33), noting
the abundance of coleopterous insects in the scats of captives and the
rarity of individuals of all age groups during dry periods in
Colorado, commented, "It is possible that the young are even more
subterranean than the adults. Perhaps they spend their early years in
rodent or other burrows where there is a fairly abundant insect fauna.
Increasing size might force them to the surface for feeding, with a
daily return to a burrow for resting and protection."
[Illustration: FIG. 25. Composition of the population of
_T. o. ornata_ at the Damm Farm based on the 194 individuals
marked there in the years 1954 to 1956. Individuals smaller
than 100 mm. ordinarily could not be sexed accurately and are
shown as open bars. Open bars in the groups larger than 100 mm.
are for females, whereas solid bars are for males.]
My own experience in the field has shown that small examples of _T.
ornata_ are not so rare as previous workers have believed. Small box
turtles occupy the same microhabitat as do the adults and seem not to
be more aquatic or subterranean in habits. Juveniles are found in
burrows, in marshy areas, and in other sheltered places, but so are
adults. Most of the juveniles that I found were in open situations
where adults were abundant, sometimes within several inches of a place
where an adult was feeding or basking. Nearly every one of the smaller
turtles was discovered when I was closely scrutinizing some other
object on the ground; sometimes juveniles were actually touched before
being seen. Most juveniles were covered with cow dung or mud and
blended so well with the substrate that they were detected only when
they moved. It is likely that only a small number of the young box
turtles present in an area is ever actually observed. Young are more
vulnerable to predation and injury because of their small size, soft
shells, and immovable plastra. They evidently rely, to a large extent,
on inconspicuousness for protection.
[Illustration: FIG. 26. The seasonal abundance of females of
_T. o. ornata_ based on 540 adults captured at the Damm Farm,
the Reservation, and on roads in eastern Kansas, in the years
1954 to 1956. Records are grouped in periods of 30 days, the
periods beginning with the dates shown at the bottoms of the
bars. Juveniles are not considered. Numbers at the top of each
bar indicate the size of the sample (both sexes) and give an
approximate indication of relative seasonal abundance of
adults, except for August, when little field work was done.]
MOVEMENTS
The only previous study of movements of _T. ornata_ is that of Fitch
(1958:99-101). He recovered 14 marked _T. ornata_ at the Reservation a
total of 30 times, the period between recaptures varying from one to
seven years. He reported that the average radius of home range was 274
feet (for an area of approximately 5.4 acres), excluding a single
(presumably gravid) female that moved 1830 feet in 53 days.
Although published information on _T. ornata_ is scant, a considerable
amount of information is available concerning its congener, _T.
carolina_. The classic studies of Stickel (1950) on it constitute the
most complete account of populations and movements for any reptile or
amphibian, and probably, for any vertebrate. She found the average
home range of adults to be 350 feet in diameter. Home ranges were not
defended as territories and nearly all individuals were socially
tolerant of one another. Movements (studied by means of a
thread-trailing device) were characterized by frequent travel over the
same routes within the home range. Some turtles concentrated their
activities in only one part of the home range, moving subsequently to
another part, and some turtles had two ranges between which they
traveled at varying intervals. Females ordinarily left their home
ranges to nest.
Other noteworthy, but less detailed, studies of populations of _T.
Carolina_ are those of Breder (1927) who found evidence of home range
and homing behavior, and of Nichols (1939b) who, after observing a
marked population on Long Island over a period of twenty years, found
evidence of homing behavior and estimated normal home range to be
approximately 250 yards in diameter. Numerous shorter papers such as
those of Schneck (1886) and Medsger (1919) document the tendency of
_T. carolina_ to remain in restricted areas over long periods.
Important studies that indicate the presence of home range and homing
behavior in other chelonians are those of Cagle (1944) on _Pseudemys
scripta_ and _Chrysemys picta_, and of Woodbury and Hardy (1948) on
_Gopherus agassizi_. Grant (1936) and Bogert (1937) have also
indicated that movements of individuals of _Gopherus agassizi_ are
restricted to limited areas.
Locomotion
Ornate box turtles moving forward over even terrain hold the plastron
a quarter to a half inch above the ground and keep the head and neck
lowered and extended. Each foreleg is brought forward and the humerus
points nearly straight ahead when the foot touches the ground. Nearly
all of the palmar surface is initially in contact with the ground but
as the body is brought forward and the humerus swings outward, only
the claws, and finally, only the two inner claws are in contact with
the ground. Of the hind feet, the medial surfaces are the principal
parts that touch the ground but some traction is derived from the hind
claws at the beginning of each cycle of the hind leg. Under normal
conditions, box turtles move slowly and pause to rest and examine
their surroundings every few feet. When resting, the plastron is in
contact with the ground, the legs relaxed, and the head and neck are
extended upward. Some turtles seeking shelter from the heat of
sunshine walk rapidly for a hundred feet or more without pausing.
Turtles seen feeding under natural conditions displayed remarkable
agility in making lunges, consisting of one or two short steps and a
thrust of the head, at moving objects. Turtles kept in my home were
able, after being conditioned to hand-feeding, quickly to intercept a
grape rolled slowly across a linoleum-covered floor.
Frederick R. Gehlbach told me that, of several species of captive
turtles observed by him, _T. ornata_ characteristically walked with
the plastron held well above the substrate, as did _Gopherus
berlandieri_, but that _T. carolina_ (specimens from the northeastern
U. S.) dragged their shells as they walked. Apparently _T. carolina_
in Kansas (currently referred to the subspecies _triunguis_) differs
somewhat in gait from populations in the eastern part of the range;
several individuals of _T. carolina_ from Kansas that I observed in
captivity, kept their plastra raised well above the smooth, hard
substrate over which they walked.
Box turtles at the Damm Farm were able easily to climb ravine banks
that sloped at an angle of 45 degrees and, with some difficulty, could
climb banks as steep as 65 degrees. Most individuals, however, were
reluctant to walk directly downward on banks as steep as 45 degrees.
Several individuals were seen to lose footing when climbing up or down
a steep bank and to roll or slide to the bottom. Ordinarily, _T.
ornata_ is able to climb over a sheer surface as high as its shell is
long, provided the surface is rough enough to give some traction to
the foreclaws. The claws of first one, then the other forefoot are
placed over the top of the barrier and then a hind foot, extended as
far forward as possible, secures a hold as the turtle goes over the
barrier.
A number of observations on speed were made in the field where
distance traveled and time elapsed were known approximately. Speeds
ranged from 20 to 100 feet per hour in the course of foraging. Higher
speeds (400 or more feet in one hour) were for turtles moving along
pathways or seeking shelter. Gould (1957:346) observed somewhat faster
speeds in _T. carolina_ (192 feet per hour in cloudy weather and 348
feet per hour in sunny weather); he observed individuals that had been
removed from their normal home ranges.
Individuals of _T. ornata_ that were placed in water swam moderately
well but were clumsy in comparison to individuals of more aquatic
emyids such as _Pseudemys_ and _Chrysemys_. Box turtles were never
observed to swim voluntarily, although they were frequently found in
shallow water. On several occasions I confronted individuals at the
edge of a pond so that the only unblocked route for their escape was
through deeper water; nearly always these individuals attempted to
crawl past me, to crawl away in shallow water parallel to the shore,
or to hide in soft mud at the edge of the water. Box turtles floated
high in the water with the dorsal side upward and had little
difficulty in righting themselves when turned over. The head and neck
are extended and submerged when the turtle is swimming; forward
progress is interrupted every few moments to elevate the head,
presumably for purposes of breathing and orientation. The shell is
never submerged. The swimming of _T. ornata_ is in general like that
of _Pseudemys_ or _Chrysemys_ that have become dehydrated after long
periods out of water and cannot submerge. These more aquatic turtles,
however, quickly overcome their bouyancy, whereas examples of _T.
ornata_, even if left in water for several days, are unable to
submerge. Clarke (1950) saw an ornate box turtle swim a 60-foot-wide
stream in Osage County, Kansas; his description of swimming agrees
with that given above.
The meager swimming ability of _T. ornata_ is of apparent survival
value under unusual conditions and enables _T. ornata_ to traverse
bodies of water that would act as geographic barriers to completely
terrestrial reptiles; however, swimming is a mode of locomotion seldom
used under ordinary circumstances.
Gehlbach (1956:366) and Norris and Zweifel (1950:2) observed
individuals of _T. o. luteola_ swimming in temporary rain pools and
small ponds in New Mexico; the two authors last named saw an
individual quickly enter a pond and dive beneath the water after being
startled on the bank. Several of my colleagues, in conversation, have
also reported seeing _T. o. luteola_ in small bodies of water in the
southwestern United States.
Daily Cycle of Activity
The daily cycle of _T. ornata_ consists basically of periods of
basking, foraging, and rest that vary in length depending upon
environmental conditions. Turtles emerge from burrows, forms, and
other places of concealment soon after dawn and ordinarily bask for at
least a few minutes before beginning to forage; foraging is combined
sometimes with basking, especially in open areas that are suitable for
both kinds of activity. Foraging usually continues until shelter is
sought sometime between mid-morning and noon. Turtles remain under
cover (or continue to forage in shaded areas) until mid-afternoon or
late afternoon when they again become active. They forage in both
morning and afternoon. Study of travel records of a few of the turtles
equipped with trailers suggests that, under normal conditions,
activity is slightly greater in forenoon than in afternoon, but that
the converse is true of gravid females seeking nesting sites. Strecker
(1908:79) reported that captive _T. ornata_, after developing a
feeding reflex, ate and retired until feeding time next day.
As environmental temperatures rise in summer, the period of mid-day
quiescence is lengthened. In the hottest part of the year, some
turtles remain under cover for several days at a time. In periods of
clear, cool weather at the beginning and end of the growing season,
some turtles remain abroad and bask for most of the day.
Examination of thread trails showed that activity of all individuals
except nesting females was terminated at dusk. Breder (1927:236),
Allard (1935:336), and Stickel (1950:358) reported a corresponding
lack of nocturnal activity in _T. carolina_. _Terrapene o. ornata_ in
Kansas, and _T. o. luteola_ in New Mexico (Norris and Zweifel,
1950:2)--unlike desert tortoises, _Gopherus agassizi_, which are
active at night in hot weather (Woodbury and Hardy, 1948:186)--do not
utilize the hours of darkness for foraging, even in the hottest part
of the year.
Seasonal Cycle of Activity
Data obtained by mapping the movements of turtles that were equipped
with trailing devices made it possible to compare distances traveled
in the course of daily activities at different times of the year. Some
of these data are expressed graphically in Figure 27. It should be
noted that movement at all times in the season of activity was uneven;
that is to say, an individual would move several hundred feet each day
for a period of several days, and then, for an interval of one to
several days, move only a few feet from one shelter to another, or not
move at all. Such periods of rest could not be correlated definitely
with environmental conditions; some individuals were inactive on days
that were probably ideal (in terms of moderately warm temperatures and
high humidity) for activity of box turtles. Analagous rest periods
were noted in _T. carolina_ by Stickel (1950:358).
Two males of _T. ornata_ that had been removed by me from their normal
home ranges traveled the longest average distance per day (429 feet).
Gravid females in June traveled the next longest average distance per
day (363 feet). The average distances traveled per day by non-gravid
females in June (226 feet) and July (260 feet) and by males (within
their known home ranges) in June (289 feet) were thought to
approximate normal amount of movement under average environmental
conditions. Average distance traveled per day by females in October
(152 feet) was shortest because of frequent and extended rest periods.
Nevertheless, in October actual distances traveled on days of activity
tended to be longer than in any other month. A gravid female traveled
farther in a single day than any other individual of _T. ornata_
observed; she moved along a rock fence for approximately 700 feet,
then left the study area and moved, in a nearly straight line, 1,200
feet across a cultivated field. Then the thread on her trailer was
expended. The total distance moved, therefore, was at least 1,900 feet
and probably more.
[Illustration: FIG. 27. Average distances traveled per day by
males and females at different times of the year, determined by
mapping of thread trails at the Damm Farm. The diagram for
"homing males" represents the distances traveled by two males
removed from their normal home ranges to test homing ability.
The data presented are for an aggregate of 136 days of
trailing. Vertical and horizontal lines represent,
respectively, the range and mean. Open and solid rectangles
represent one standard deviation and two standard errors of the
mean, respectively.]
An adult male at the Reservation traveled 2,240 feet in the 36-day
period from October 16 to November 20, 1954, mostly on a wooded
hillside. Eleven forms found along the route of the turtle's travels
indicated that movement took place on roughly one out of three days in
the elapsed period and demonstrated the sporadic nature of movements
in autumn. The turtle remained active for an undetermined time after
November 20.
Home Range
Data obtained from trailing and various methods of recapture at the
Damm Farm indicated that each individual used only a small part of the
total study area in the course of daily activities and tended to
remain within a restricted area for a long time.
The number of recaptures of no individual was great enough to permit
application of refined calculations of size of home range as described
by Odum and Kuenzler (1955). For individuals that were recaptured six
or more times, or individuals for which adequate trailing records were
available, the area enclosed by a line joining the peripheral points
of capture was considered adequately representative of the home range
of that individual, unless recaptures were all within a few feet of
each other or lay in an approximately straight line. If less than six
records of recapture were available, home range was estimated, in the
manner described by Fitch (1958:73), by averaging the distance between
successive points of recapture and letting this average represent the
radius of home range; the actual area of home range was determined by
the formula, [pi](R)², for the area of a circle.
Size of home ranges of males and females did not differ significantly
and data for the two sexes were combined in the final analysis. The
average radius of the home ranges of 44 adults (captured a total of
146 times) was 278 feet (extremes, 71 to 913) when computed by
measuring the distance between successive captures; the average area
of these home ranges was 5.6 acres. Data from 10 turtles that had been
recaptured only once were combined with data from 34 turtles that had
been recaptured more than once when it was found that the average size
of home range in these two groups did not differ significantly. Data
concerning the home ranges of eight of the 44 individuals were
sufficient to permit actual measurement of home ranges with a
planimeter; home ranges of these eight individuals had an average area
of five acres (extremes, 1.2 to 10.2).
A minimum home range could theoretically consist of the smallest area
in which adequate food and shelter were available. Under favorable
conditions a turtle could stay in an area ten to twenty feet in
diameter. Although several such favorable small areas existed on the
Damm Farm, box turtles seldom stayed in one for more than a day or
two. Seemingly, therefore, factors additional to food and shelter
influence size of home range. At the Damm Farm these additional
factors seemed to be: rock fences that acted as physical barriers;
areas that were cultivated, barren, or otherwise unfavorable, acting
as ecological barriers; and, cowpaths and ravines that offered
relatively unobstructed routes along which box turtles tended to move.
One subdivision of the main pasture, the northwest corner area, is an
example of a relatively small natural area in which many individual
box turtles had home ranges. This tract of 28 acres was roughly
triangular and was bordered on two sides by rock fences that contained
no gates or other passageways. On its third (southeastern) side the
area sloped into a deep ravine. Habitat in this subdivision of the
pasture (as well as in the other two subdivisions) was especially
favorable for box turtles because of permanent water, rocky slopes,
ravines, and several fruit trees. Box turtles usually foraged near the
rock fences and the ravine (where dung was more abundant than in other
parts of the area), and tended, as they foraged, to move parallel to
these barriers. Turtles crossing the area eventually came either to
one of the fences or the ravine. Therefore, most of the turtles in the
northwest corner area eventually completed a circuit of the area.
Turtles that came to the ravine tended to move along its bottom or
sides. Several turtles were known to cross the ravine and to forage in
the grassy area on its southeastern side. These turtles usually
re-entered the ravine by way of smaller side-ravines. Of 22 box
turtles known to have home ranges in the northwest corner area, only
two individuals (both gravid females) were known to leave the area in
the period in which observations were made.
Two other subdivisions of the main pasture--the house pond area and
the southern ravine area--although not so distinct as the northwest
corner area in terms of limiting barriers, nevertheless constituted
separate areas of favorable habitat, each of which contained a number
of individual home ranges. Although the two areas were not far apart,
but little movement was observed of turtles from one area to the
other. The home range of only one turtle, an adult female, was known
to include parts of both areas.
Unbroken expanses of tall grass seem not to be optimum habitat. The
crest of the hill at the Damm Farm (Pl. 17, Fig. 1) was an area of
more or less homogeneous grassy habitat. Turtles were seldom found on
the crest of the hill although this area was as thoroughly searched
for turtles as any other area. Known home ranges of nearly every
individual observed were on either one of the sides of the hill but
not on both sides.
At several places on the border of the pasture, turtles were able to
move freely into cultivated areas but seldom did so except for
nesting. Trailing records show that most of the turtles that entered
one of the cultivated areas returned again to the pasture.
Ornate box turtles seem to find places of shelter by trial and error
along regularly used routes of travel in their home ranges. The
individuals that I studied never returned to the same forms, and
seldom returned to the same natural burrows and dens. Probably
foraging, basking, and watering sites are found also by trial and
error.
Stickel (1950:375) placed considerable importance on the occurrence of
transient turtles in populations of _T. carolina_; in estimating
population density, she added to her study area a peripheral strip,
half as wide as the average, estimated home range, to account for
turtles that had home ranges only partly within the study area. The
study area used by Stickel had no natural boundaries, as habitat
conditions on all sides were essentially the same as those of the
study area itself. The pasture at the Damm Farm, on the contrary, is a
relatively isolated area of natural grassland, bordered by rock
fences and cultivated fields. I believe that most of the box turtles
found on the pasture were permanent residents there. Individual box
turtles at the Damm Farm seemingly occupied but one home range and it
did not change from year to year. Populations of _T. ornata_ in areas
less isolated than the Damm Farm, like the populations of _T.
carolina_ studied by Stickel (_loc. cit._), could be expected to have
a higher percentage of transient individuals and individuals with
multiple or changing home ranges. Henry S. Fitch told me that he
considered most of the individuals of _T. ornata_ that were captured
only once at the Reservation were transients.
Several females at the Damm Farm traveled long distances from their
home ranges to nest but other females nested within their known or
estimated home ranges. Seemingly a complex of environmental factors,
including soil texture, weather, availability of water, and possibly
the urge for random wandering in the breeding season, governs the
distances traveled by gravid females and the ultimate selection of a
satisfactory nesting site. Females, because of their more extensive
travels in the nesting season, seem more likely than males to have
multiple or changing home ranges. Males of _T. ornata_ did not
noticeably alter the extent or pattern of their movements in the
breeding season. Hibernacula, unlike nesting sites, were within the
known or estimated home ranges of all individuals studied.
[Illustration: FIG. 28. The movements of an adult (non-gravid)
female of _T. o. ornata_ in the house pond area at the Damm
Farm during a period of 24 days in July, 1955 (solid line), and
a period of three days (broken line) in July, 1956. Solid dots
represent the points where the turtle was found as her thread
trail was mapped; hollow symbols represent points of recapture
when no trailing thread was attached to the turtle.]
The actual home range of almost every individual studied, even
of those individuals for which the most data were available, probably
differed at least slightly from the observed or estimated home
range. One adult female, for example, was captured six times in
two years within a radius of approximately 50 feet. Another female
was found 2780 feet from her last point of capture. These last
two records were regarded as unusual; when they were grouped
with records of the 44 individuals mentioned above, the average
radius of home range for the entire group was much larger (327
feet).
[Illustration: FIG. 29. The movements of a gravid female of
_T. o. ornata_ in the southern ravine area at the Damm Farm in
a period of ten days in June, 1956. Her movements were, for the
most part, in and around several ravines (shown on map by
broken lines) where she was searching for a nesting site. For
explanation of symbols see legend for Fig. 28.]
Homing Behavior
Gould (1957) reported that 22 of 43 _T. carolina_ moved in a homeward
direction when they were released in open fields up to 5.8 miles from
their original points of capture. Turtles oriented themselves by the
sun; homeward headings were inaccurate or lacking on overcast days
and, light reflected from a mirror caused turtles to alter their
courses. Seven of ten turtles released more than 150 miles from home
headed in directions that corresponded most nearly to the headings
last taken (at release-points near home base) and did not necessarily
correspond to the direction of home. Gould's studies point out that
box turtles perhaps practice a kind of "solar navigation." His work
raises the question of whether the movements of box turtles are guided
by the sighting of local landmarks or whether such landmarks alter the
course of movement only when acting as barriers.
In the present study two experiments were made to determine the homing
ability of _T. ornata_. An adult male, taken from his normal home
range in the house pond area and released 1200 feet away in the
southern ravine area, traveled a generally northward course (not
northeastward in the direction of home) for five days, moving a
distance of approximately 1900 feet. His detached trailer was
recovered several days later 740 feet southeast of the last known
point in his travels (a distance that could have been covered in two
days) and 150 feet from the point of original capture; he had returned
to his home range by a circuitous route in a period of approximately
seven days. Another adult male, captured in the southern ravine area,
and released in the house pond area 1900 feet away, traveled on a
course that bore approximately 25 degrees north of true homeward
direction; after five days he was approximately 600 feet north of the
original capture point. He then began a northeastward course that took
him back to the house pond area where he remained for several days; no
further data are available for this individual. It is significant that
the homing males discussed above traveled greater average distances
per day (based on records for nine days of trailing) than any of the
other turtles studied (Fig. 27). Fitch (1958:101) released an
individual one half mile from where he captured it and, one year
later, recovered the turtle near the point of release.
Social Relationships
Ornate box turtles are solitary except during periods of mating.
Meetings with other individuals in the course of foraging, basking, or
seeking shelter, are fortuitous and have no social significance. A
broad overlapping of home ranges of both sexes at the Damm Farm
suggests that box turtles do not intimidate other individuals in the
home range or exclude them from it. No instances of fighting were
observed.
Allard (1935:336), Perm and Pottharst (1940:26), and Latham (1917)
recorded instances of fights between individuals of _T. carolina_; in
the latter two instances fights were between males. Stickel (1950:362)
observed an incident between two males that may have been a fight;
however, she was of the opinion that fights rarely occur in nature and
that box turtles do not defend territories. Evans (1954:23-25)
considered the behavior of _T. carolina_ reported by Perm and
Pottharst (_loc. cit._) to represent "territoriality." He found "... a
true hierarchy...." existing between four captive males of _T.
carolina_ and another between three captive females of the same
species; young individuals in the group raised their social level in
the hierarchy after receiving experimental doses of male hormone.
Evans (_op. cit._:25) pointed out that true tortoises (family
Testudinidae) have a more complex pattern of social behavior than do
emyid turtles.
Observations made with binoculars from the vantage point of a blind
provide the only information that I have concerning the reactions of
box turtles to one another under natural conditions. Turtles foraging
in a bare area were not startled by the approach of other turtles, and
turtles moving across the area seemed to take no notice of turtles
already there, regardless of whether these turtles were moving or not.
Adults and subadults behaved in approximately the same manner.
Individuals traveling or foraging in rough terrain or in grassy areas
probably are unable to see each other even when they are close to one
another. Conversely, box turtles can see each other and are surely
aware of each other's presence in bare, flat areas. These facts
suggest that no social hierarchy exists in _T. ornata_. On one
occasion an adult male and a juvenile (hatched the previous autumn)
were found foraging next to one another on the same pile of cow dung.
When an individual became motionless in an attitude of wariness after
having detected me in my blind, its behavior evoked no response on the
part of other turtles, a few feet away.
INJURIES
Fire, freezing, molestation by predators, and trampling by cattle or
native ungulates are only a few natural sources of injury to which box
turtles have always been exposed. Man's civilization in the Great
Plains, chiefly his automobile and other machines, have compounded the
total of environmental hazards. Automobiles now constitute a major
cause of death and serious injury to box turtles. Each year thousands
are struck on Kansas highways alone, not to mention the many
casualties resulting from mowing machines, combines, and other farm
machinery.
Although grass fires usually occur in early spring or late fall when
box turtles are underground, some turtles are surely killed by fires
and many are injured. In early April of 1955 the pasture at the Damm
Farm was burned. Similar burnings, I discovered, had occurred both
intentionally and accidently in past years at irregular intervals. No
deaths or injuries, attributable to fire were discovered in the course
of intensive field work in the spring and summer of 1955, when the new
grass was short and conditions for finding and marking box turtles
were ideal. Badly burned individuals, if any, may have secreted
themselves until their wounds had healed. In June, 1957, an adult
female, that had been burned severely, was taken from a small puddle
in a ravine on the Damm Farm. The soft parts of her body, excepting
her head and neck, were a nearly solid mass of smooth scar tissue, the
scales and rugosities of the skin being practically obliterated. The
tail was reduced to a mere knob surrounding the anus and dead, exposed
bone was visible on most of the dorsal part of the carapace. Possibly
this female was burned in the fire of 1955. Lack of injury to the head
and neck can probably be accounted for by the additional protection
afforded these parts by the folded forelegs when the turtle was
withdrawn in the shell.
Turtles that are smashed flat on the highway, of course, have no
chance of survival. Highway fatalities are usually the result either
of "direct hits," where the tire of a vehicle passes directly over the
turtle, or of repeated pummeling by subsequently passing vehicles. The
writer, while driving behind other cars that struck turtles or by
sitting beside roads, has observed numerous turtle casualties. Most
are struck a glancing blow by a tire and are propelled some distance
through the air or on the surface of the pavement, often to the side
of the road. Such a blow is usually sufficient to crack or chip the
shell, or at least to scuff away parts of the epidermal covering.
Turtles, so injured, usually survive.
Parts of the shell do not break away easily, even when several deep
cracks are present, and only a little bleeding occurs. A common injury
inflicted on the highway is the wrenching and subsequent dislocation
of the carapaco-plastral articulation. In such instances the
ligamentous tissue joining the two parts is torn extensively. Under
these circumstances the movable shell parts seem to act as a safety
device, giving way under pressure that would crack the shell of a
turtle with rigid, fixed buttresses. Dislocations of the
carapaco-plastral articulation that have healed are characterized by
abnormally heavy development of ligamentous tissue, which may
elaborate a horny, scutelike substance on its outer surface.
The extent to which serious injury incapacitates a turtle is not
known. Surely open wounds are susceptible to infection and to various
kinds of secondary injury; normal activity is probably interrupted by
a period of quiescence, at least in the period of initial healing.
An injured female had a hole, slightly more than one inch in diameter,
in the right side of the carapace at the level of the second lateral
lamina. A tight, thin membrane stretched between the broken edges of
the opening; this membrane contained no bone and was covered
externally by scar tissue. It was obvious that this turtle had
recovered, at least in part, from a serious injury (inflicted probably
by a piece of heavy farm machinery).
Minor chips, scratches, and abrasions on the shell result from a
variety of sources, some of them mentioned above. Small rounded pits
in the bony shell (shell pitting) due to causes other than mechanical
injury, are found in nearly all kinds of turtles according to
Carpenter (1956), Hunt (1957), and my personal observation. In _T.
ornata_, however, the condition is less common than in the specimens
of _T. carolina_ described by Carpenter and in the remaining species
of _Terrapene_ that I have examined.
Carpenter (1956:86) came to no conclusion as to the cause of shell
pitting in _Terrapene carolina_ but suggested that a variety of
factors including parasitic fungi, parasitic invertebrates, and simple
shell erosion, might be responsible.
According to my own observations on turtles in the University of
Kansas collections, shell pits range in size and shape from shallow,
barely discernible depressions to deep borings; I suspect that shell
pitting for turtles in general has many causes, some of which may be
of more frequent occurrence in one species than in another.
Hunt (1957:20) presumably was referring to shell pitting by a more
suitable name when he wrote of, "... necrosis ... of mycotic origin."
Hunt (_loc. cit._) stated that "Of those cases which have been
recently examined, the author found all were due to the invasion of
Mucorales beneath the plates of the epidermal laminae. This disease is
of extremely common occurrence and has been found in all members of
the order but is seldom found in marine species. Mycosis more
frequently occurs on the plastron than on the carapace." Hunt
presented no evidence to support his statement regarding invasion of
the shell by Mucorales.
Evidence that injury to the soft parts of the body is also fairly
common is seen in the many _T. ornata_ with missing feet and legs.
Stumps resulting from amputations are covered with tough, calloused
skin and sometimes by horny tissue similar to that of the antebrachial
scales. Amputees are incapacitated only slightly in normal locomotion
if a functional stump remains; probably a cripple is somewhat
handicapped in other functions, such as burrowing, nest digging
(females), and copulation (males). Causes of amputation are discussed
in the section on predators.
Fractures of the limb bones are common. A female from Stafford County,
Kansas (Pl. 29, Fig. 4), showed a typical case of fracture and
subsequent repair; the right fibula had been broken and the ends
dislocated; a great mass of bone joined the repaired break to the
middle of the tibia, giving the entire skeleton of the leg the
appearance of the letter "H." The fibula, shortened by the
dislocation, no longer articulated by its proximal end with the femur;
the tibia probably bore the entire load in the period of repair and
the transverse connection that formed between the bones later took
over the function of the fibula.
There is little doubt that ornate box turtles are stepped on or
trampled by cattle, at least occasionally, but I never observed such
an incident; the predilection of ornate turtles for dung insects and
for moving along cattle pathways brings them to close quarters with
cattle and probably did likewise with native ungulates. A steer,
stepping on a box turtle, could inflict superficial damage to the
shell or cause broken limbs but would probably not crush the turtle
unless on a hard substrate.
REPAIR OF INJURIES TO THE SHELL
Most adults and a few juveniles examined in the field and laboratory
had one or more small injuries on the carapace that had healed or were
undergoing repair. Such injuries almost never occurred on the
plastron. In an injury that was undergoing repair, a small piece of
smooth, whitened bone was exposed where a piece of epidermis was
missing from the shell. One or more edges of the exposed bone
characteristically projected over the surrounding epidermis, making
the bone appear as though it had been driven forcefully, like a
splinter, into the shell (Pl. 29, Figs. 1 and 2). Because of their
curious appearance, small areas of repair were referred to in my notes
as "splinter scars." The position and number of splinter scars were
often recorded as supplementary means of individualizing turtles in
the field.
Splinter scars result from minor abrasions that damage a few square
millimeters of the shell. Larger areas of exposed bone were noted in
only a few specimens. Two turtles at the Damm Farm had bone exposed on
more than one-half the surface area of the carapace; both of these
turtles were probably burned in the grass fire of 1955. Ordinarily, a
break in the shell does not induce extensive regeneration of tissues;
when shells are damaged by crushing or cracking, regeneration of
epidermis and bone occurs only along the lines of fracture, unless the
broken parts have been dislocated. Ligamentous tissue develops in some
breaks on the plastron, the broken area remaining slightly movable
after healing is completed (Pl. 24).
Dissection of injured shells revealed the mode of shell regeneration
to be the same whether a large or small portion of the shell had been
damaged. An abrasion may gouge out a small portion of the shell;
burning, freezing, or concussion may kill a portion of the epidermis
and a corresponding portion of bone beneath it without actually
disfiguring the shell. Dead bone and epidermis become loosened at the
margin of the wound. The epidermis sloughs off soon afterward but the
bone adheres to the wound. New epidermis and new bone, growing from
undamaged tissues at the edges of the wound, encroach on the wound
beneath the layer of dead bone. The piece of dead bone is thereby
gradually isolated from the rest of the shell and is sloughed off when
healing is complete. The dead bone may come off in one piece or slough
off gradually at its edges as healing proceeds toward the center of
the wound. The layer of dead bone protects the wound during the
process of regeneration (Pl. 30). Areas of exposed bone become white
and shiny, nearly enamellike in appearance, as a result of wear on the
shell.
The above conclusions, in regard to _T. ornata_, agree basically with
the findings of Woodbury and Hardy (1948:161-162) and Miller
(1955:116) on regeneration of the shell in desert tortoises (_Gopherus
agassizi_). Danini (1946:592-4, English summary) made histological
studies on regeneration of the shell in specimens of _Emys
orbicularis_; he found that new bone trabeculae formed on the surfaces
of undamaged trabeculae at the edge of the wound and formed also in
connective tissue at the center of the wound. Regeneration of bone was
incomplete in some instances where total extirpation of a portion of
the shell had occurred. Regenerated epidermis was usually thicker than
the original scute.
Exposed bone on the shells of turtles that have been injured in fires,
although dead, is unmarked and shows no evidence of being burned.
Exposure to fire kills the growing portions of both the epidermis and
the bone but seemingly does not actually char or disfigure the bone
(although the epidermis may be so affected) (Pl. 29, Fig. 3). Injuries
from fire result probably from brief encounter with the fire itself or
from more prolonged contact with some surface heated by the fire. A
turtle that remained in a fire long enough to have its shell charred
would presumably have little chance of survival. Grossly disfigured
shells therefore do not result directly from burns but are due to the
gnarled texture of the regenerated bone and epidermis remaining after
the dead portions of the shell have been sloughed off. Information on
injuries from fire was supplemented by examination of several badly
burned specimens of _T. carolina_. Their shells were nearly covered
with exposed bone and regenerated epidermis. One specimen was so badly
damaged that the entire anterior rim of its carapace was loose and
could be pulled away easily to disclose a gnarled mass of regenerating
bone beneath it (Pl. 29, Fig. 3). There were areas near the posterior
margin of the carapace of each specimen where regenerated epidermis
was evident but where the bone was seemingly uninjured; the
regenerated epidermis was nearly transparent.
Areas of regenerated epidermis on specimens of _T. ornata_ were rough
in texture and slightly paler than the surrounding scutes.
Color-pattern is not reproduced in the process of regeneration but
irregularly shaped light blotches sometimes occur in the places where
radiations or other distinct markings formerly were present. A slight
depression remains on the shell after regeneration is completed. I
suspect that small injuries may be repaired in the course of a single
growing season but that injuries involving a large part of the shell
may take several years to heal completely. Cagle (1945:45) reported
that a bullet wound in the shell of a painted turtle (_Chrysemys
picta_) healed completely in approximately 23 months. Danini (_loc.
cit._) found that regeneration of the shell in _Emys orbicularis_ was
complete in as short a time as 225 days. Woodbury and Hardy (_loc.
cit._) stated that small injuries to the shell of _Gopherus agassizi_
may take as long as seven years to heal.
ECTOPARASITES
Two kinds of ectoparasites were found on ornate box turtles in the
course of the present study; larvae of chigger mites (_Trombicula
alfreddugesi_) were abundant on specimens collected in summer and,
larvae of the bot fly (_Sarcophaga cistudinis_) were found on
specimens throughout the season of activity, and, in a few instances,
on hibernating turtles. In general, these ectoparasites do little or
no harm to ornate box turtles, although heavy infestations may cause
temporary interruption of normal activity or may even cause occasional
death.
Concerning the larvae of _T. alfreddugesi_, Loomis (1956:1260) wrote,
"In northeastern Kansas, larvae become numerous in early June (shortly
after they first appear), increase in numbers to greatest abundance
throughout late June and July, decrease slightly in August, become
markedly reduced in September, and only a few larvae (mostly on hosts)
remain in October and early November." He considered _T. alfreddugesi_
to be the most abundant chigger mite in Kansas and stated (_op.
cit._:1265) that it is most common "... in open fields supporting good
stands of grasses, weeds and shrubs, and where moderate to large
populations of vertebrates are present." Loomis listed ornate box
turtles (_op. cit._:1261-2) as important hosts of _Trombicula
alfreddugesi_ but noted that box turtles are not so heavily infested
as are certain other reptiles. The two other species of chigger mites
that Loomis (_op. cit._:1368) found on _T. ornata_ in Kansas (_T.
lipovskyana_ and _T. montanensis_) were not found in the present
study.
Box turtles were considered to have chigger infestations when the
reddish larvae could be detected with the unaided eye. No chiggers
were seen on turtles in the period from spring emergence until June
13, 1955. On the latter date a few scattered chiggers were noted on
several individuals and it was on this same date that the writer
received his first "chigger bites" of the year. Numbers of chiggers
increased in the latter half of June and heavily infested turtles were
noted throughout July. No chiggers were seen on box turtles after
mid-September in 1955.
Chiggers were ordinarily found only on the soft parts of the turtles'
bodies. Early in the season infestations were chiefly on the head and
neck. Favorite sites of attachment were the point where the skin of
the neck joins the carapace and on the skin around the eyes. Later in
the season some chiggers could be found on nearly every part of the
body where soft skin was present; concealed areas of skin, such as the
axillary and inguinal pockets, the anal region, and the inner rim of
the carapace (where it joins the skin of the body), harbored
concentrations of chiggers. Juveniles were relatively more heavily
infested than adults and, even early in the season, had chiggers
attached along many of the interlaminal seams of the shell. Broad
areas of soft, newly-formed epidermis on the shells of juveniles
probably afforded a better place of attachment to chiggers than did
the interlaminal seams of adults. The interlaminal seams and
transverse hinges of adults were not infested until the height of the
season of chigger activity. Heavily infested adults, observed in early
July, were literally covered with chiggers; red larvae outlined nearly
all the scutes of the shell, the anus, the mouth, and the eyes. When
turtles were picked up for examination, chiggers could be seen moving
rapidly from one interlaminal seam to another.
Box turtles kept in outdoor pens and in the laboratory did not long
maintain visible infestations of chiggers, even during the time in
summer when turtles found in the field were heavily infested.
A four-year-old juvenile was found nearly immersed in the shallow
water of a pond on July 4, 1955; its right eye had been damaged by an
especially heavy concentration of chiggers. When I released the
turtle, some 50 feet from the pond, it returned to the water and spent
the next four days there. The turtle was probably in a period of
quiescence induced by the eye injury and the heavy infestation of
chiggers; immersion in water could be expected to help free the turtle
of chiggers and to relieve trauma resulting from the injured eye.
Richard B. Loomis told me that larval chiggers are able to survive
under water for several days but that warm water will hasten their
demise.
Infestations of larval bot flies (_Sarcophaga cistudinis_) were noted
in several turtles at the Damm Farm and, upon closer scrutiny, were
found to be common in preserved specimens from other areas. Larvae
were always found in flask-shaped pockets (Pl. 27, Fig. 2) beneath the
skin; the pockets opened to the outside by a small hole, the edges of
which were dried and discolored. One larva sometimes protruded from
the opening. The inside of the pocket is lined with smooth, skinlike
tissue. Heavily infested box turtles may have four or five such
pockets, each containing one to many larvae. The most frequent sites
of the pockets are the skin of the axillary and inguinal regions, and
the skin of the limbs and neck, especially near the bases of these
members. Subadults were more heavily infested than older adults; no
infestations of hatchlings or small juveniles were noted.
An adult female, infested with bot fly larvae when she was removed
from her hibernaculum in late October, 1955, bore no trace of larvae
or of the pocket that had contained them when she was recaptured the
following June. According to Rokosky (1948), the larvae eventually
fall to earth and pupate. The individuals of _T. carolina_ studied by
him were not re-infested by adult bot flies; one turtle ate some of
the larvae that dropped from its body.
The manner in which box turtles are infested by bot fly larvae is
uncertain. Possibly the eggs are picked up accidentally or laid on the
skin while box turtles are foraging in dung. Belding (1952:841)
classifies the genus _Scarophaga_ as semi-host-specific, depositing
eggs in open wounds.
McMullen (1940), Rodeck (1949), and Rainey (1953), described
individuals of _T. ornata_ parasitized by _S. cistudinis_. Rokosky
(1948) and Peters (1948:473) reported infestations in _T. carolina_.
Infestations were the cause of death in the instances noted by Rainey
and Rokosky.
PREDATORS
Few first-hand observations on predators of _T. ornata_ are available
and I have found little direct evidence of predation in the course of
this study. In general, adults of the species seem to have few natural
enemies other than man. Several of my colleagues at the University of
Kansas have observed dogs carrying box turtles in their mouths or
chewing on them. Frank B. Cross told me his dog caught and ate young
_T. ornata_ in Payne County, Oklahoma, and A. B. Leonard once saw a
badger carrying one in Dewy County, Oklahoma. At the Reservation, a
freshly killed juvenile was found beneath the nest of a crow (_Corvus
brachyrhynchos_) and remains of a hatchling were found in a scat of a
copperhead (_Agkistrodon contortrix_).
Dr. Fred H. Dale, Director of the Patuxent Research Refuge, Laurel,
Maryland, kindly furnished photostatic copies of cards, from the
Division of Food Habits Research of the U. S. Fish and Wildlife
Service, recording the instances in which _Terrapene ornata_ was
listed as a food-item. In one instance the stomach of each of two
nestlings, in the same nest, of the White-necked Raven (_Corvus
cryptoleucus_) in Terry County, Texas, contained remains of recently
hatched ornate box turtles; the remains of one turtle made up 64 per
cent of the contents of one stomach, and parts of three turtles made
up 80 per cent of the contents of the other stomach. Each of two
stomachs of the coyote (_Canis latrans_) from Quay County, New Mexico,
contained a "trace" of ornate box turtle.
Wild carnivores known to occur on the Damm Farm were raccoons
(_Procyon lotor_), striped skunks (_Mephitis mephitis_), badgers
(_Taxidea taxus_), and coyotes (_Canis latrans_); all were suspect as
predators of ornate box turtles.
On December 10, 1953, ten dead box turtles (eight adults and two
juveniles) were discovered at the top of a cut bank on the Damm Farm,
within a few feet of a burrow that was used at least part of the time
by a striped skunk. The condition of the turtles suggested that they
had lain in the open for several weeks. The heads and legs were
missing from most of the turtles and tooth marks were discernible on
several of the shells. A logical explanation of this occurrence is
that the turtles, using the burrow as a hibernaculum, were ousted by a
predator that also inhabited the burrow. Turtles moving about
sporadically in late autumn may be quickly chilled by a sudden drop in
temperature and therefore be more susceptible to predation than at
other times of the year. Two of my colleagues at the Museum of Natural
History informed me that they had observed similar concentrations of
dead _T. ornata_ in winter.
In July, 1952, H. B. Tordoff collected eight shells of juvenile _T.
ornata_ in a dry creek bed near Sharon, Barber County, Kansas. Some of
the shells had small tooth-punctures. The stream bed habitat and the
appearance of the tooth punctures tended to incriminate raccoons as
predators. Raccoons, more than any other carnivore mentioned above,
possess the manual dexterity necessary to pry open the shell of a box
turtle and bite away the soft parts. Badgers and possibly coyotes are
probably the only local carnivores (excluding large dogs) that could
crack open the shell of an adult turtle by sheer force.
Adults of _T. ornata_, since they occasionally molest small juveniles,
must be considered in the category of predators. When captive adults
and juveniles were fed from the same container in the laboratory, the
turtles occasionally bit one another accidently. Serious injury to the
young was prevented by watching the adults closely and moving them
away when they caught a smaller turtle by the leg or head. Similar
accidents presumably occur in nature; juveniles and adults were
sometimes found feeding side by side. William R. Brecheisen told me
that adults kept in a stock tank at his farm in the summer of 1955
regularly and purposefully chased and bit small juveniles in the same
tank. Brecheisen gave me a juvenile that had been so bitten; the right
side of its head was badly damaged (the eye gone and a portion of the
bony orbit broken) but was partly healed. Ralph J. Donahue told me
that he saw an adult _T. ornata_ attack a juvenal _T. carolina_, and
provided a photograph of the incident. The juvenile was not injured.
Although small box turtles may occasionally be caught and killed by
adults in nature, this seems not to constitute a major source of
predation on the young.
Other animals that may prey upon young box turtles occasionally (and
that were known to occur at the Damm Farm) are bullsnakes (_Pituophis
catenifer_), red-tailed hawks (_Buteo jamaicensis_), marsh hawks
(_Circus cyaneus_), crows (_Corvus brachyrhynchos_), and opossums
(_Didelphis marsupialis_), and domestic cats.
Nest predators probably have greater effect on populations of _T.
ornata_ than do predators of hatchlings, juveniles, and adults. Four
robbed nests were found at the Damm Farm; in each instance, striped
skunks were thought to be the predators. E. H. Taylor told me that he
once saw a bullsnake swallow an entire clutch of newly laid eggs
before the female turtle could cover the nest.
DEFENSE
Box turtles rely for protection on the closable shell and on
inconspicuousness; defense reactions, except in the rare instances
that biting is provoked, are purely passive.
Box turtles handled in the course of field work varied widely in their
reactions. Many struggled violently when being measured or marked
whereas others were completely passive, closing the shell tightly and
making it difficult for me to examine the soft parts of the body.
These differences in behavior did not seem to be correlated either
with sex or with age; generally lessened activity was associated with
suboptimum body temperatures. All box turtles found in the field were
extremely wary. As soon as one sighted me (sometimes at a distance of
200 feet or more), it became motionless with shell raised from the
ground and neck extended (Pl. 28, Fig. 5). Some turtles remained in
this motionless stance for half an hour or more, finally moving slowly
away if I remained motionless. Turtles made no attempt to escape until
I approached them closely or until they were in danger of being
trampled by my horse; they would then move away with remarkable
rapidity. Box turtles seemed unaware of an intruder until he could be
seen or until he touched the turtle. When a turtle was approached from
the rear, whistling, finger snapping, and normal footfalls did not
attract its attention. Latham (1917:16) observed corresponding
behavior in _T. carolina_. Wever and Vernon (1956) found the ear of
_T. carolina_ to be keenly sensitive to sounds in the range of 100-600
cycles per second but progressively less sensitive to sounds of higher
and lower frequencies. Surely a predator as stealthy as a coyote could
approach a box turtle unseen and could quickly bite off at least one
of the turtle's legs. Many of the mutilated box turtles that I
observed may have survived such encounters with carnivores. The
tendency of some individuals, when handled, to over-extend the limbs
and neck (rather than closing the shell) in an attempt to escape,
would make them easy victims for any predator.
Ornate box turtles were kept in my home, along with several cats.
Initial behavior was characterized by mutual wariness; subsequently
the cats would follow a turtle about the house for a time,
occasionally pawing at an exposed limb. The turtles withdrew only when
touched or when approached from the front. After a day or two the cats
and turtles ignored each other, often eating and drinking from the
same dishes without incident. Under these circumstances the cats, I
believe, could easily have killed or injured the turtles. A turtle
would occasionally gain the respect of a cat by biting it.
The strong odor sometimes given off by box turtles is produced by the
secretions of four musk glands, two situated anteriorly on each side
and opening by small, nearly invisible apertures beneath the fourth
marginal scute. According to Hoffman (1890:9), two other musk glands,
opening beneath the eighth marginal scute on each side, are also
present in _Terrapene_; these posterior glands were not found in the
several specimens of _T. ornata_ that I dissected.
Strong odors were produced by nearly all small juveniles until they
became accustomed to being handled. Older juveniles and adults
produced strong odors only in response to pain or injury, as, for
example, when they were killed in the laboratory prior to preservation
or when they were being marked in the field. Young box turtles were
capable of producing strong odors as soon as they hatched.
Norris and Zweifel (1950:3) considered the odor produced by _T. o.
luteola_ to issue from the "... concentrated, highly pungent
urine...." voided by individuals when they were disturbed, and thought
the production of odor to be a defense mechanism. Neill (1948b:130)
reported that hatchlings of _T. carolina_ with unhealed umbilical
scars emitted a musky odor comparable to that of the stinkpot,
_Sternotherus odoratus_; he thought the capacity to produce this odor
was lost at about the time that the plastral hinge became functional.
The function of musk glands in _Terrapene_ and, in all other turtles,
is unknown. Since biting and nuzzling of the edges of the shell is an
integral part of the courtship of many turtles, odor produced by the
musk glands may well be a means of social recognition or of sexual
stimulation. Repellant odor may have a protective value in young box
turtles but it is unlikely that larger predators would be frightened
away or even discouraged by odor alone. In this respect Neill (_loc.
cit._) and I concur.
DISCUSSION OF ADAPTATIONS
Most of the morphological characteristics distinguishing box turtles
from other North American emyid turtles, the most notable of which is
the movable plastron, are modifications that have evolved as a result
of selectional pressures favoring adaptation to more or less
terrestrial existence. Similar adaptations have arisen independently
in several branches of the emyid stock (see introduction). The genus
_Terrapene_ seems to have departed farther from a generalized emyid
form than have other kinds of box-turtle-like chelonians. In a
morphological sense, _Terrapene ornata_ is clearly the most
specialized member of its genus now occurring in the United States
(my own studies have revealed that populations in western Mexico now
referred to as _T. klauberi_ and _T. nelsoni_ are as specialized as
_T. ornata_ in some respects but more generalized in others). The
present ecological study has demonstrated that _T. ornata_ is
specialized in habits as well as in structure. It is concluded that
these specializations (of more generalized and perhaps more primitive
conditions as, for example in _T. carolina_) constitute adaptation for
terrestrial existence in open, semiarid habitats. These adaptations in
_T. ornata_ have resulted, in a few instances, in unique habits and
structures; however, in most instances the adaptations have produced
slight but recognizable changes that are definable only by degree of
difference from other species of box turtles.
The closable shell of box turtles is of obvious survival value in
providing protection for the soft parts of the body. In most of the
species of _Terrapene_, the lobes of the plastron completely close the
openings of the shell; closure is so tightly effected in some
individuals that it is difficult to insert the blade of a knife
between the adpressed margins of carapace and plastron. In _T. ornata_
nevertheless, both lobes of the plastron are deficient on their
lateral margins; four narrow openings remain when the lobes are drawn
shut. Emargination of the plastron has occurred at the places where
the limbs rub against it during locomotion. This reduction of the
plastron permits the body to be held off the ground during forward
locomotion and seemingly permits a generally freer range of movement
for the limbs. The possible disadvantages of an imperfectly closable
shell seem to be compensated for by increased mobility. Reduction of
the plastron is correlated with a general lightening of the shell,
probably associated with the increased vagility of this species.
Lightening of the shell is evident also in the relatively thin,
loosely articulated bony elements. Shells of adult _T. ornata_ that
are old and weathered, or macerated (unless they are partly
co-ossified because of injury), can nearly always be disarticulated
with ease, whereas the bony elements in the shells of adult _T.
carolina_ (all races) are nearly always co-ossified or separable only
after prolonged maceration.
The relatively low, flattened shell of _T. ornata_ is an adaptation
associated with the tendency to seek shelter in the limited space of
earthen forms, burrows, or small natural cavities in the course of the
warm season and to burrow more deeply into the ground in winter.
_Terrapene ornata_ is, in fact, the only species of the genus that may
be considered an habitual burrower. Individuals of _T. carolina_ tend
to seek shelter in the warm season by making forms in dense vegetation
or by digging into yielding substrata such as mud or humus, although
they may burrow deeply into the earth in winter. Extreme weakness or
absence of the middorsal keel of _T. ornata_ seems to be a
modification associated with burrowing habits and general adaptation
to terrestrial life; the keel is similarly reduced in testudinids.
Retention of epidermal laminae (as opposed to regular exfoliation of
the older parts of scutes) occurs in all box turtles, in several other
groups of terrestrial emyids, and in testudinids. The phenomenon is
here considered to be a specialization of scute shedding--developed in
terrestrial and semiterrestrial chelonians--that provides additional
protection to the shell against wear and minor injuries.
General shortening of digits--the result of reduction in number of
phalanges as well as in their length, and to a lesser degree the
shortening of metapodial elements--has occurred in several groups of
chelonians with terrestrial tendencies (the opposite--lengthening of
phalanges and metapodials, and hyperphalangy--has occurred in certain
groups that are highly aquatic). The pes of box turtles has remained
relatively unchanged in this respect; a few phalanges on the lateral
digit have been lost (especially in three-toed forms), but little
reduction in length has occurred. The chief modification of the pes is
a general narrowing brought about by the tendency of the digits to be
crowded together, one on top of the other, rather than spread in a
horizontal plane. Considerably more modification is seen in the manus
of _Terrapene_. Phalangeal formulae (expressing the number of
phalanges from the first digit outward) range from 2-3-3-3-2
(primitive in _Terrapene_) to 2-3-3-2-2 in the races of _carolina_ and
have the same range in the species of eastern Mexico. Extreme
reduction in number (2-2-2-2-2) as well as general shortening of
phalanges occurs in _T. ornata_. The formula is the same in the one
specimen of _T. klauberi_ that has been skeletonized. This
modification of the forelimb in _T. ornata_ has produced a more rigid,
stronger manus that is well adapted to the requirements of burrowing
and to locomotion over unyielding substrata. Shortening of the manus
(and, to a lesser extent, the pes) has been accompanied by reduction
and loss of interdigital webbing. It is noteworthy that _T. ornata_
has achieved the same reduction in number of phalanges as _Gopherus_,
which displays the extreme of specialization in this respect among
North American turtles. The manus in _T. ornata_ is not shortened so
much as in _Gopherus_.
The first toe in males of _T. ornata_ is uniquely widened, thickened,
and inturned. Males of some other species of _Terrapene_ have greatly
enlarged rear claws, some of which turn slightly inward, but none has
the flexed first toe hooklike as it is in _ornata_ (a modified first
toe, resembling that described for _T. ornata_, has been observed in a
live male of _T. klauberi_ [now KU 51430] since the preparation of
this manuscript). In males of _T. ornata_ the penultimate phalanx of
the first toe has a normal, vertical articular surface on its proximal
end. However, the distal articular surface (when viewed from the
distal end of the phalanx) has its axis rotated away from the vertical
plane approximately 45 degrees in a counterclockwise direction. As the
foot is pronated and extended, and as the digits are flexed, there is
a concomitant inward rotation of the first metatarsal at its proximal
joint; this rotation, combined with the divergent planes of the
articulating surfaces on the penultimate phalanx, cause the ungual
phalanx to be flexed at right angles to the inner side of foot, in a
plane perpendicular to that of the other toes (Fig. 21).
The precise function of the modified first toe of males is unknown,
although it is reasonably safe to assume that the modification is
closely associated with clasping during coition. In the matings that I
observed, the inturned first claw of the male secured a hold on the
female's rump or just beneath her legs, whereas the remaining three
toes gripped the edge of her plastron. The combined hold, on shell and
skin, clearly affords the male a more secure position during coitus
(whether the female clasps his legs with hers or not) than would a
hold on skin or shell alone. Possibly intromission can be maintained
in this position even when the female is attempting to escape. In
males the plastron is less concave in _T. ornata_ than in _T.
carolina_. Furthermore, males of _T. ornata_ are, on the average,
smaller than females, whereas the reverse is true in _T. carolina_.
Possibly the ability of the male to secure an especially firm grip on
the female enhances the probability of small males mounting and
inseminating larger females, whereas successful matings might
otherwise be limited to pairs in which the male was the larger member.
It is worthy of note that turtles of the genus _Terrapene_ are
seemingly the only North American emyids that carry out the entire
process of mating on land; other, semiterrestrial emyids (for example,
_Clemmys insculpta_ and _Emydoidea blandingi_) return to water for
actual coition, although the precoital behavior sometimes occurs on
land.
Nearly all gradations from a fully developed zygomatic arch to a
greatly reduced arch can be observed in skulls of the various species
of _Terrapene_ (Fig. 2) (Taylor, 1895:586, Figs. 2-7). The highest
degree of reduction is achieved in _T. ornata_ and _T. klauberi_, both
of which lack the quadratojugal bone and have no zygomatic arch
whatever (except for an occasional, poorly defined anterior vestige
formed by the postfrontal, the jugal, or both). Reduction of the
zygoma clearly represents modification of a more generalized, complete
arch. As yet there is no clear evidence that reduction of the
zygomatic arch is of adaptive value. It is noteworthy, however, that
similar reduction of the arch has occurred independently in a number
of emyid and testudinid groups, nearly all of which have terrestrial
or semiterrestrial habits. Although discussion of phyletic lines in
_Terrapene_ is beyond the scope of this report, I tentatively suggest
that reduced zygomatic arches have arisen independently in more than
one group of _Terrapene_ and that similar reduction of the arch in two
species of the genus does not necessarily indicate an especially close
relationship of such species.
In a recent survey of cloacal bursae in chelonians, Smith and James
(1958:88) reported _T. ornata_ and _T. mexicana_ to be among the few
emyids that lacked these structures; in the opinion of the authors
(_op. cit._:94) cloacal bursae evolved in chelonians that required an
accessory respiratory organ for long periods of quiescence
(hibernation or aestivation) under water, and were secondarily lost in
terrestrial forms that hibernated on land. The assumption is a
reasonable one, at least in regard to emyids and testudinids. Lack of
cloacal bursae in _T. ornata_ and in all testudinids, can be
correlated with the completely terrestrial habits of those turtles.
Cloacal bursae seem to be vestigial in the species of _Terrapene_
possessing them and to be of little or no use as respiratory
structures (except perhaps in _T. coahuila_).
In most of the species of _Terrapene_ the carapace has a pattern of
pale markings on a darker background; however, unicolored individuals
are the rule in certain populations (for example, at the western edge
of the range of _T. carolina_ and in _T. ornata luteola_) and occur as
occasional variations in other populations (in _T. yucatana_, _T.
mexicana_, and, throughout the range of _T. carolina_, albeit more
commonly in the southeastern part of the range). Personal observation
of interspecific and ontogenetic variation of color patterns of box
turtles has convinced me that a basic pattern of more or less linear
radiations is the one from which all other patterns (including spots,
blotches, rosettes, and the unicolored condition) can be derived, and,
that the radial pattern is generalized and primitive for _Terrapene_
(possibly for all emyids and testudinids as well). In the light of
this conclusion, the radial pattern of _T. ornata_ may be considered
generalized. I suspect, however, that the pattern of a living species
most closely approaching that of the primitive ancestral stock of
_Terrapene_ is the pattern of fine, wavy, dark radiations (on a paler
background) present in young examples of _T. coahuila_.
Box turtles in general have lower reproductive potentials (as
indicated by fewer eggs and longer prepuberal period) than do most
aquatic emyids. This low potential seems to be compensated for by a
lower rate of postnatal mortality (especially in adults) due to the
protection afforded by the closable shell and the ability to recover
from serious injury. _Terrapene o. ornata_ and _T. c. carolina_ are
the only box turtles the life histories of which are known well enough
to permit significant comparison. The reproductive potentials of _T.
o. ornata_ and _T. c. carolina_ seem to be much the same.
[Illustration: PLATE 15]
Aerial photograph of Damm Farm (July, 1954).
Numbers and letters on photograph denote the following:
1. Main pasture with subdivisions
a to c, respectively, northwest corner area,
house pond area, and southern ravine area;
2. Wooded area; and,
3. Cultivated area.
[Illustration: PLATE 16]
FIG. 1. A water-filled ravine in the northern part of the
pasture at the Damm Farm (June 28, 1958). The subdivision of
the pasture referred to in text as "northwest corner area" can
be seen sloping into the ravine from the west (left
background).
FIG. 2. A cow path leading southward away from a ravine, at the
Damm Farm (June 28, 1958). Ornate box turtles used such paths
as routes of travel in the course of their daily activities.
[Illustration: PLATE 17]
FIG. 1. Grassland on crest of hill at Damm Farm with
northeastern corner of main pasture in background (June 29,
1958).
FIG. 2. A bare area along the rock fence at northern edge of
pasture at Damm Farm. Ornate box turtles could nearly always be
found foraging in cow dung here and in similar areas along
other fences (June 28, 1958).
[Illustration: PLATE 18]
FIG. 1. A ravine in the southern part of the pasture at the
Damm Farm (June 28, 1958). Small springs at the heads of such
ravines produced marshy conditions at their bottoms and
provided drinking water, in the form of shallow pools, for box
turtles for at least part of the year. Banks of ravines
provided suitable sites for the construction of nests and
forms.
FIG. 2. A mulberry tree on the bank of a ravine near northern
edge of Damm pasture (June 28, 1958). Box turtles frequented
the area beneath the tree when fruit fell to the ground in June
and July. The ravine shown here filled with water after being
dammed in June, 1956.
[Illustration: PLATE 19]
Representative stages in the spermatogenic cycle of
_T. o. ornata_ (all specimens obtained in Douglas County,
Kansas, 1955).
FIGS. 1 to 5, respectively, are sections of seminiferous tubules
obtained on May 17, June 14, July 15, Aug. 31, and Oct. 4.
FIG. 6: seminiferous tubule of immature male (plastral length,
88 mm.), six years old, obtained on June 30.
FIG. 7: section of epididymis from mature male obtained on
April 17, three days after turtle emerged from hibernation;
mature sperm form a continuous dark mass in center of
epididymis.
FIG. 8: sperm in uterine portion of oviduct of female obtained on
April 18, 1954.
Figs. 1 to 6 and 8 were photographed à 430, and were enlarged
1.4 times. Fig. 7 was photographed à 35, and was enlarged
1.4 times.
[Illustration: PLATE 20]
FIG. 1. Left ovary of mature female, prior to ovulation,
May 15, 1956 (Ã 1).
FIG. 2. Fresh corpus luteum, June 2, 1956 (à 4½).
FIG. 3. Testes of mature male, August 31, 1955 (Ã 1).
FIG. 4. Testes of mature male, April 14, 1956 (Ã 2).
FIG. 5. Left ovary of subadult female (seven years old, plastral
length, 114 mm.) that would have matured in approximately one
year (à 1½).
FIG. 6. Left ovary of juvenal female (11 years old, plastral length,
95 mm., à 1½).
[Illustration: PLATE 21]
FIG. 1. A trial nest cavity excavated by a gravid _T. o. ornata_
at the Damm Farm on June 8, 1956. The cavity was situated at
the edge of a grassy area on the upper rim of a ravine
embankment. Twelve-inch ruler shows scale.
FIG. 2. A depression, resulting from an old post-hole, showing
the openings made by three box turtles as they left their
hibernacula in April, 1956 (photographed May 15, 1956).
Twelve-inch ruler shows scale.
[Illustration: PLATE 22]
FIG. 1. Right abdominal lamina (à 2½) of a four-year-old
juvenal male showing method of measuring growth-rings. The
last growth-ring (4) was formed at the end of the 1954 growing
season. The first growth-ring (H) marks the end of the season
of hatching (1950). The umbilical scar (U) is faintly visible.
The growth-zone for 1955 (specimen captured June 23) is just
beginning to show in interlaminal seam.
FIG. 2.
_Left_--Right abdominal lamina (Ã 2) of subadult female, eight
years old. The last growth-zone was formed in 1954. Note
the relatively small growth increments in 1952 and 1953.
The growth-zone for 1955 (date of capture, May 8) is not
yet visible. This specimen grew more in the season of
hatching (1946) than the specimen shown above in Fig. 1.
_Right_--Interpectoral seam (Ã 3) of adult male showing
slowness of growth in later life. The widest growth-zone
seen here was formed in the tenth year and is followed by
four zones too narrow to measure accurately. It is uncertain
whether this specimen was still growing in the year it was
captured (1923).
[Illustration: PLATE 23]
Ontogenetic change in color and markings of carapace. Radial
markings begin to develop at the onset of epidermal growth.
Markings are sharply defined in juveniles and young adults but
may be obscured in later life by the encroachment of dark
ground color or by wear on the shell.
Figures are as follows:
_Upper left_--Hatchling (à 1½);
_Upper right_--Juvenile (Ã 1), one year old;
_Lower left_--Juvenile (Ã 1), one year old;
_Lower left_--Female (Ã 7/16) showing typical adult markings;
_Lower right_--Adult male (à ½showing blotched pattern
resulting from wear on shell.
[Illustration: PLATE 24]
Ontogenetic change in color and markings of plastron. Dark
markings on plastra of hatchlings are unbroken. Dark radiations
appear when epidermal growth begins.
Figures are as follows:
_Upper left_--Hatchling (à 1½);
_Upper right_--Juvenile (Ã 1);
_Lower left_--Female (Ã 7/16) showing typical adult markings;
_Lower right_--Adult male (à ½) showing the effect of wear
on markings. Plastra of old individuals are sometimes solid
yellow. Note the break in the plastron that has healed and
filled with ligamentous tissue.
[Illustration: PLATE 25]
Ontogenetic change and sexual dimorphism in shape, color, and
markings of head and neck. Females retain much of the juvenal
pattern of spots and blotches. In males, the top and sides of
the head become greenish or bluish and markings are obscured.
FIGS. 1 and 3. Lateral and dorsal views of hatchling (à 3½);
FIGS. 2 and 4. Lateral and dorsal views of juvenile (Ã 2);
FIGS. 5 and 6. Adult female (Ã 1);
FIGS. 7 and 8. Adult male (Ã 1) showing relatively wider and more
truncated snout in this sex.
[Illustration: PLATE 26]
FIG. 1. A foraging station next to a rock fence at the Damm
Farm (June 28, 1958). The box turtle in foreground was in the
act of tearing apart a pile of partially dried cow dung to
obtain dung insects.
FIG. 2. A depression (à ½) made by a foraging box turtle in a
pile of partially dried cow dung (June 28, 1958). Similar
"sign" of box turtles was found in cow dung everywhere on the
pasture at the Damm Farm.
[Illustration: PLATE 27]
FIG. 1. Thread-laying device ("trailer") taped to the carapace
of an adult female _T. o. ornata_. The squares of tape on the
sides are to keep the bent-over ends of the wire axle from
catching on vegetation (à ½).
FIG. 2. A dermal pocket ("cyst") removed from an adult
_T. ornata_ and cut open to show two larval bot flies
(_Sarcophaga cistudinis_) (Ã 2, May 15, 1956).
[Illustration: PLATE 28]
FIGS. 1-3. Stages in courtship of _T. o. ornata_: male pursuing
female and biting her shell; male lunging at female in attempt
to mount; and, male just after mounting female (à ¼).
FIG. 4. _T. o. ornata_ smelling food (Ã 1).
FIG. 5. _T. o. ornata_ in attitude of alertness after detecting
intruder (Ã 3/8).
FIG. 6. Tracks of _T. o. ornata_ in muddy ravine (Ã 1/8) (June 5,
1956).
[Illustration: PLATE 29]
FIG. 1. A small, nearly-healed, injury on the carapace of an
adult _T. o. ornata_ (Ã 2). Note regenerated epidermis at
bottom of depression and two pieces of dead bone ("splinter
scars") at upper right margin of depression.
FIG. 2. Injured area on the carapace of a juvenal _T. o. ornata_
(Ã 3) with dead bone removed and laid to the right, exposing
regenerating epidermis in its early stages.
FIG. 3. Anterior edge of carapace (held away with forceps) of
specimen of _T. carolina_ (KU 51461, Gulf Co., Florida) that
had been badly burned (Ã 8/9). Nearly all the scutes of the
shell had fallen off and large pieces of dead bone could be
pulled away, exposing a gnarled mass of regenerating bone and
epidermis.
FIG. 4. A fracture that has healed and joined the tibia (upper bone)
to the fibula in a specimen of _T. o. ornata_ (KU 1877, à 3½).
[Illustration: PLATE 30]
_Top_: A shell of _T. o. ornata_ (à ½) as it was found at the
Damm Farm June 1, 1956. A serious injury (probably resulting
from burns) had exposed a large area of dead bone on the
carapace.
_Center_: Same shell with some of scutes removed.
_Bottom_: Same shell with dead bone removed to expose
regenerating epidermis and bone. Note that the injury involved
several of the neural bones; the turtle probably died as a
result of this injury but not before regeneration was
approximately one-half completed.
_Terrapene ornata_ seems to concentrate its breeding season (laying,
incubation, and hatching of eggs) more nearly in the middle of the
warm season than does _T. c. carolina_. This concentration probably is
an adaptation for breeding in open habitats where, under environmental
temperatures less equable than in forest, eggs would develop more
rapidly and hatch sooner but would be less able to survive winter
temperatures.
Males of _T. o. ornata_ become sexually mature when younger and
smaller than females and rarely grow as large as females. Nichols
(1939a:20) indicated the reverse to be true of _T. c. carolina_;
Nichols further indicated that growth continued some six to eight
years after puberty. Most individuals of _T. o. ornata_ attain maximum
size within two to three years after puberty.
Although it is difficult to be certain about the adaptive value of
color and pattern, it seems that in box turtles, as in many other
kinds of animals, patterns and colors most nearly blending with those
of the habitat have some selective value in providing concealment from
enemies. The pattern of linear radiations in _T. o. ornata_ closely
resembles the patterns formed by light passing through grasses and
associated vegetation and camouflages the turtle. In a similar manner,
partial or complete loss of radial markings in _T. o. luteola_ seems
to provide concealment in habitats where vegetation is sparse and
where blending with the substrate is of survival value. The patterns
of blotches and broken radiations in most of the subspecies of _T.
carolina_ likewise provide camouflage by tending to match patterns
formed by the light passing through a leafy canopy.
Although ornate box turtles are omnivorous, they probably depend on
insects as a dietary staple. In years when preferred kinds of insects
were unusually abundant, the turtles grew more than in other years. A
large proportion of the insects eaten is obtained by foraging in or
near dung. Alteration of the dung community--at least in a physical
sense, but presumably also by influencing the successional stages of
the dung biota--is one of the few evident effects of box turtles on
the environment. Although certain kinosternids (Carr, 1952:93), emyids
(Deraniyagala, 1939:257; Loveridge and Williams, 1957:198), and
testudinids (Loveridge and Williams, _op. cit._:247) eat mammalian
feces, _T. ornata_ is seemingly the only chelonian that habitually
seeks its staple diet in dung. The habit seems to be yet another
specialization for terrestrial existence. The carnivorous habits of
_T. ornata_ reverse the general trend toward omnivorous and
herbivorous habits in other turtles that have become partly (emyids)
or wholly (testudinids) terrestrial.
It seems remarkable that none of the species of true tortoises
occurring in the grasslands of the world has developed insectivorous
habits or utilized the unique food niche (in regard to dung-foraging)
filled by ornate box turtles in the Great Plains; tortoises are, as
far as is known, strictly herbivorous. The ranges of _Gopherus_ and
_Terrapene_ are now almost mutually exclusive and the two kinds do not
compete with each other for food in the few places where they occur
together. It is known, however, that box turtles (_T. longinsulae_,
_ornata_-like, earliest known box turtle) and true tortoises (genera
_Testudo_ and _Gopherus_, see Williams, 1950:25-26, Fig. 2) occurred
together in what is now the Great Plains in early Pliocene times and
probably for some time before and after this. Assuming that food
habits of fossil representatives of these genera were somewhat like
the habits of recent representatives, ornate box turtles may have
developed insectivorous habits at a time when other food niches were
filled by herbivorous tortoises. Box turtles possibly survived
subsequent changes in habitat that made it impossible for populations
of large tortoises to exist in the Great Plains.
SUMMARY
Box turtles of the genus _Terrapene_ are emyid turtles that are
specialized for terrestrial existence. Two of the seven species now
recognized--_T. ornata_ and _T. carolina_--occur in the United States.
_Terrapene carolina_ inhabits forested areas in the east whereas _T.
ornata_ is characteristic of open grassy areas in the west; the ranges
of the two species overlap in the broad belt of prairie-forest ecotone
in the central United States. _Terrapene ornata_ is considered to be
the most specialized of living box turtles.
The natural history of _T. o. ornata_ Agassiz was studied in the
period, 1953 to 1957. Intensive field studies were made in Douglas
County, northeastern Kansas, on a small area of prairie and on the
University of Kansas Natural History Reservation. Field observations
were made also in a number of other places in eastern Kansas.
Laboratory studies supplemented field studies.
Habitats occupied are chiefly open areas; they vary in regard to food
supply, temperature, moisture, and kind of soil. The grassy prairies
of Nebraska, Kansas, Oklahoma, and northern Texas seem to provide
optimum habitat for ornate box turtles; in these areas box turtles are
active on a majority of days from April to October. The subspecies
_luteola_ is adapted to the more rigorous and arid environment of the
southwestern United States, where activity may be possible for only a
few weeks in the year. The remainder of the year is spent in a state
of quiescence. Factors limiting the distribution of _T. ornata_ are:
1) the presence of a substrate too hard to permit digging of nests and
forms (altitudinal distribution in southwestern United States and
distribution at western edge of the range); 2) temperatures causing
the ground to freeze deep enough (approximately 30 inches) to kill
turtles in hibernacula (northern edge of range); and, 3) the lack of
one or more relatively wet periods in the course of the warm season,
preventing at least temporary emergence from quiescence (southwestern
part of range). The activities of man probably have affected
population density in local areas but limit the geographic range only
in the north (Blanchard, 1923:19-20, 24) where intensive cultivation
probably has excluded the species.
Preferred habitat in northeastern Kansas is open rolling grassland
grazed by cattle; populations are most dense near natural breaks in
the grassy vegetation such as fences, scattered rocks on hillsides,
ravines, and stream-beds.
Mating occurs most commonly in spring and autumn; courtship behavior
includes pushing and biting on the part of the male. In coitus the
hind legs of the male are held tightly by the female; the male falls
backward after coitus, still clasped by the female. A few sperm are
stored in the oviducts; fertilization without reinsemination can
occur. The spermatogenic cycle begins in May and reaches its peak in
September, when large numbers of sperm and spermatids are present in
the testes; the cycle is completed in October, when sperm pass into
the epididymides. The testes are smallest in spring and largest in
September. Females are inseminated with sperm produced in the
preceding year. The ovarian cycle begins in midsummer, soon after
ovulation, and continues up to the time of the next ovulation.
Follicular growth is rapid in the period from spring emergence to
ovulation. Large follicles remaining after ovulation represent, in
many instances, eggs that will be laid later in the same season.
Follicular atresia is never great enough to account for the
destruction of all large follicles remaining after ovulation. All
mature females lay at least one clutch of eggs per year. It is
estimated that one-third of the females produces two clutches of eggs
in a single season. Second clutches contain fewer eggs than first
clutches. An alternation of ovarian activity occurs, whereby one ovary
is more active than its partner in one season and less active in the
next season. Alternating activity of ovaries accounts in part for the
reduced number of eggs in young females, breeding for the first time,
and in older, nearly senile females. Extrauterine migration of ova
results usually in a more even distribution of eggs in the oviducts.
Corpora lutea constitute an accurate record of the number of eggs
produced by the ovary as well as the number of eggs laid.
Nesting occurs from May through July but is most common in mid-June;
some of the females nesting early in the season lay a second clutch of
eggs in July. Nests are dug in the earth by the female using her hind
legs. Preferred nesting sites are open, well-drained places with a
soft substrate. The nesting site is selected after a period of
wandering, in which the female tests the substrate at a number of
places; some females search for a nest site for more than a week. Nest
digging begins in the evening and is usually completed after dark.
Captive females dug a preliminary cavity in which the body rested
during the digging of the main nest cavity. The entire clutch of eggs
is laid in one nest. The average number of eggs in 23 clutches was 4.7
(range, 2 to 8). The average size of eggs tends to be inversely
proportional to the number of eggs in a clutch. Eggs increase in bulk
by absorption of water in the course of incubation. Immersion in water
for short periods does not harm eggs. The incubation period under
favorable environmental conditions is approximately 65 days; cool,
damp conditions prolong the incubation period and probably constitute
an important factor of prenatal mortality in certain years. Eggs that
do not hatch before winter probably do not survive. Emergence of
hatchlings from the nest may, however, be delayed until spring if the
soil is dry in autumn. Hatchlings can probably escape freezing by
burrowing into the walls of the nest. Infertility and prenatal
mortality account for at least 40 per cent of the eggs laid, according
to laboratory findings. Progeny of a single adult female (considering
factors of mortality, multiple layings, and average age of puberty)
would number approximately 300 after 20 years. Reproductive processes
probably continue throughout life, although possibly at a somewhat
reduced rate in later life.
Young box turtles are active soon after hatching but become quiescent
if allowed to burrow in soil or if they are covered with damp cotton.
Some captive hatchlings take live food in the first days of life but
others do not eat until the following spring; initiation of growth is
coincident with initiation of regular feeding. The yolk sac retracts
mainly during hatching; it sometimes ruptures after hatching. The
caruncle remains on the beak for a variable length of time, but never
is present in the spring following hatching.
Major growth-rings on the epidermal laminae are formed regularly, one
after each season of growth, in the first 10 to 14 years of life.
Minor growth-rings occur between major rings and are shallower. Growth
of epidermal laminae results from the formation, in spring, of a new
layer of epidermis beneath the existing scute. The peripheral
projection of the new layer is distinct in texture and color from the
older part of the scute and is separated from it by a major
growth-ring. Minor growth-rings form when growth slows or temporarily
stops during periods of quiescence; no new layer of epidermis is
formed. Growth-rings constitute an accurate record of growth that can
be studied at any time in the life of the turtle; they are accurate
indicators of age only as long as regular annual growth persists.
Growth in the season of hatching depends on early hatching and early
emergence from the nest. Turtles that remain in the nest until spring
probably do not grow. Slightly less than half of the free-living
individuals studied grew in the season of hatching. Precociousness in
early life often results in the attainment of sexual maturity at an
earlier than average age.
Growth is rapid at first (increments in plastral length average 68,
29, and 18 per cent, respectively, in the first three years) and then
slows gradually until puberty. Attainment of sexual maturity is more
closely correlated with size than with age. Males mature when smaller
(76 per cent were mature when plastron 100 to 109 mm. long) and
younger (average age, eight to nine years) than females (66 per cent
were mature when plastron 110 to 119 mm. long, average age at
maturity, ten to eleven years) but females grow larger than males. A
few individuals of each sex reach puberty three to four years sooner
than average.
The average number of growing days per season is approximately 160.
Amount of growth in any season depends on climatic factors that
influence food supply and foraging conditions. Growth rate is directly
correlated with precipitation, being highest when large populations of
grasshoppers and long periods of favorable weather occur in the same
year. Zones of epidermis formed in years when growth was especially
slow or especially fast constituted landmarks that were helpful in
interpreting growth-histories. Growth stops two to three years after
puberty. The total growing period is estimated to be not more than 15
to 20 years. Longevity is estimated to be approximately 50 years.
A number of changes in structure and appearance occur in the period
from hatching to puberty. Fontanelles of the bony shell close at or
before puberty. Movable parts of the plastron are not functional until
the fourth year. Markings on the carapace change from a series of dots
to distinct, straight-sided radiations, and a similar pattern develops
on the plastron. Markings on the heads of females resemble those of
juveniles but males have greenish heads. Males further differ from
females in having a red iris, more brightly colored antebrachial
scales, and a turned in first toe.
Analysis of some 500 body temperatures (Centigrade) obtained under
natural conditions revealed the following: the optimum temperature for
activity is near 30 degrees; box turtles emerge from cover usually
when body temperature is 24 degrees or higher, and almost never when
the body temperature is below 15 degrees; body temperature is raised
to optimum by basking in open areas although activity begins at
suboptimum temperatures if basking is impossible; cover of dens,
burrows, or forms is sought when the body temperature rises above 30
degrees; and, maximum and minimum body temperatures that would be
lethal to box turtles (for prolonged periods) are approximately 40 and
zero degrees, respectively. Laboratory experiments showed speed of
response to environmental temperature to be inversely proportional to
bulk; hatchlings could be chilled or warmed more than twice as fast as
adults and were active within a narrower range of temperature. Ornate
box turtles in general are subject to a narrower range of thermal
activity than are aquatic turtles that occur in the same areas.
Box turtles are dormant approximately five and one-half months of the
year--from late October to mid-April. Warm weather in November and
late March sometimes stimulates temporary activity but dormancy is
uninterrupted from mid-November to early March. Forms, dens, and
burrows are used as hibernacula. Depth of hibernacula is dependent on
severity of temperatures and amount of vegetational cover; hibernacula
in open grassland were seven to 18 inches deep whereas those in wooded
areas were six inches or shallower. Box turtles are ordinarily
solitary when hibernating. Injuries and deaths due to freezing
probably occur in the coldest part of the winter. The lowest body
temperature of a turtle that survived a winter was 2.7 degrees; an
individual, the temperature of which was nearly zero for several days,
subsequently died. Turtles burrow upward at the end of hibernation and
remain just below the surface for a week or two before emerging. The
primary stimulus for emergence seems to be a period of warm moist
weather.
Populations of _T. ornata_ observed under natural conditions were
chiefly carnivorous, although captives ate a variety of animal and
vegetable matter. Insects, consisting chiefly of beetles,
caterpillars, and one species of grasshopper, comprised approximately
89 per cent (by volume) of the food present in stomachs. Beetles
(chiefly scarabaeids and carabids) are obtained in or near dung and
seem to constitute the most important staple element of the diet.
Piles of dung, disturbed by turtles in the course of their foragings,
were characteristic "sign" of _T. ornata_ in the areas studied.
Insects form the bulk of the diet for most of the year, although
certain other foods, when especially abundant for short periods
(mulberries for example), are eaten in large quantity or eaten to the
exclusion of all other foods. Ornate box turtles occasionally eat the
eggs and young of ground-nesting birds and slightly damage vegetables,
but in no instance do these feeding habits significantly affect the
economy of man. Box turtles probably benefit man by destroying large
numbers of crop-damaging insects (locustids and noctuid caterpillars).
Box turtles were more numerous than most kinds of reptiles at the Damm
Farm and were the most conspicuous of any kind of reptile. One hundred
and ninety-four turtles were marked; one-fourth of these were
recaptured at least twice. Population density in certain areas of
favorable habitat ranged from 2.6 to 6.3 turtles per acre. The total
number of individuals on the study area was estimated to be 286. The
marked population consisted of 53 per cent adult or subadult females,
31 per cent adult males, and 16 per cent juveniles of undetermined
sex. Only six individuals had plastra shorter than 60 millimeters.
Small box turtles are not so rare as these samples indicate; they are
infrequently obtained because their smallness and ability to blend
with the substrate make them difficult to see. More females than males
were found in all months of the season of activity, excepting April
and August when more males were found; the preponderance of females
was greatest in the nesting season (June and July).
Ornate box turtles walk with the shell held off the substrate. They
are able to climb steep embankments or low barriers with some
facility. Swimming ability is sufficient to permit survival in water
and traversal of water-barriers but ornate box turtles almost never
swim voluntarily.
Daily activity consists of periods of basking, foraging, and rest, the
durations of which are influenced by temperature and humidity. There
is no activity after dark except that of nesting females. After
several days of activity there is a period of rest; rest periods
seemed not to be correlated with climatic conditions. The average
distance traveled per day in summer is 200 to 300 feet. Movements of
gravid females are more extensive (average, 363 feet per day) than
those of other members of the population; one individual traveled
approximately one-fourth of a mile in a single day. Turtles removed
from their normal home ranges traveled farther per day than any other
group. Movements in autumn are less extensive (average, 152 feet per
day) than at other times in the season of activity.
Individual box turtles tended to remain in small areas for long
periods; these areas were interpreted as home ranges. The estimated
average radius of 44 home ranges was 278 feet (average area, 5.6
acres). The average area of eight home ranges that were actually
measured was five acres. General suitability of habitat and certain
physical features of terrain (rock fences, ravines, barren fields)
that acted as barriers were thought to be the most important factors
governing size of home range. Of two turtles removed more than
one-fourth of a mile from their home ranges, one homed and one did
not. Home ranges of turtles of all ages and sexes overlap broadly.
There was no indication that territoriality or social hierarchy
existed in the population studied.
Box turtles are subject to injury from natural causes that include
fire, cold, molestation by predators, and trampling by cattle.
Automobiles and farm machinery now constitute major causes of
mortality and serious injury. Capacity to recover after serious injury
is great but there is increased chance for secondary injury,
infection, and predation in the period of recovery. Pits on the shell
from unknown causes ("shell pitting") are less common in ornate box
turtles than in other kinds of turtles.
Ectoparasites infesting _T. ornata_ are larvae of chigger mites (genus
_Trombicula_) and larvae of bot flies (_Sarcophaga cistudinis_).
Ectoparasites usually have little adverse effect on the turtles,
although heavy infestations cause occasional injury or death.
Few natural enemies other than man are known; however most wild
carnivores as well as opossums, large birds, and domestic dogs and
cats are suspect as predators. The incidence of predation on eggs and
small juveniles is far greater than on older juveniles and adults.
Adults of _T. ornata_ occasionally attack smaller individuals.
Ornate box turtles are able to detect the presence of intruders, by
sight, from a distance of several hundred feet in open country;
apparently, intruders are not detected until seen. Defensive behavior
is passive; the shell is closed tightly in response to painful stimuli
and, in some instances, at the sight of an intruder. Juveniles usually
void odoriferous fluid from the musk glands when handled but adults do
so only in response to pain or injury. The function of the musk glands
is unknown; possibly the odor of musk is a means of sexual
identification or stimulation. Although the musk is probably
distasteful to predators, repellent odor alone seems to be of doubtful
value as a defense mechanism.
LITERATURE CITED
AGASSIZ, L.
1857. Embryology of the turtle. Contributions to the natural
history of the United States, 2(3):451-643, 27 pls.,
12 wood-cuts in text, tables. Little, Brown and Co.,
Boston.
ALLARD, H. A.
1935. The natural history of the box turtle. Sci. Monthly,
41:325-338.
1939. Mating of the box-turtle ending in death of the male.
Copeia, 1939(2):109.
ALTLAND, P. D.
1951. Observations on the structure of the reproductive organs of
the box turtle. Journ. Morph., 89:599-621, 16 figs.
AUFFENBERG, W.
1958. Fossil turtles of the genus _Terrapene_ in Florida.
Bull. Florida State Mus., Biol. Sci., 3(2):53-92, 15 figs.,
5 tables.
BAILEY, R. M.
1948. Winter mortality in the snake _Storeria dekayi_. Copeia,
1948 (3):215.
BELDING, D. L.
1952. Textbook of clinical parasitology. Appleton-Century-Crofts,
Inc., New York, viii + 1139 pp., 283 figs.
BLANCHARD, F. N.
1923. The amphibians and reptiles of Dickinson County, Iowa. Univ.
Iowa, Studies Nat. Hist., 10:19-26.
BOGERT, C. M.
1937. Note on the growth rate of the desert tortoise, _Gopherus
agassizi_. Copeia, 1937(3):191-192.
BOOTH, K.
1958. Development of eggs and young of desert tortoise.
Herpetologica, 13(4):261-263.
BREDER, R. B.
1927. Turtle trailing: a new technique for studying the life habits
of certain Testudinata. Zoologica, 9(4):231-243.
BRENNAN, L. A.
1937. A study of the habitat of the reptiles and amphibians of
Ellis County, Kansas. Trans. Kansas Acad. Sci., 40:341-347,
1 table.
BRUMWELL, M. J.
1940. Notes on the courtship of the turtle, _Terrapene ornata_.
Trans. Kansas Acad. Sci., 43:391-392.
CAGLE, F. R.
1939. A system of marking turtles for future identification.
Copeia, 1939(3):170-173, 5 figs.
1944. Home range, homing behavior, and migration in turtles. Misc.
Publ., Mus. Zool., Univ. Michigan, No. 61, 34 pp., 2 pls.,
4 figs., 5 tables.
1945. Recovery from serious injury in the painted turtle. Copeia,
1945(1):45.
1946. The growth of the slider turtle, _Pseudemys scripta elegans_.
Amer. Midl. Nat., 36(3):685-729, 8 figs., 3 pls., 13 tables.
1948. The growth of turtles in Lake Glendale, Illinois. Copeia,
1948(3):197-203.
1950. The life history of the slider turtle, _Pseudemys scripta
troostii_ (Holbrook). Ecol. Monogr., 20(l):31-54, 18 figs.,
4 tables.
1954. Observations on the life cycles of painted turtles (genus
_Chrysemys_). Amer. Midl. Nat., 52(l):225-235, 2 figs.,
1 table.
CAGLE, F. R., and TIHEN, J.
1948. Retention of eggs by the turtle _Deirochelys reticularia_.
Copeia, 1948(1):66.
CAHN, A. R.
1937. The turtles of Illinois. Illinois Biol. Monogr.,
16(1-2):1-218, 31 pls., 15 figs., 20 maps, 20 tables.
CAHN, A. R., and CONDER, E.
1932. Mating of the box turtles. Copeia, 1932(2):86-88, 2 figs.
CARPENTER, C. C.
1956. Carapace pits in the three-toed box turtle, _Terrapene
carolina triunguis_ (Chelonia-Emydidae). Southwestern
Naturalist, 1(2):83-86, 1 fig., 1 table.
CARPENTER, J. R.
1940. The grassland biome. Ecol. Monogr., 10(4):617-684, 7 figs.,
7 tables.
CARR, A.
1952. Handbook of-turtles: the turtles of the United States, Canada,
and Baja California. Cornell Univ. Press, xv + 542 pp.,
37 figs., 82 pis., 15 tables, 23 maps.
CLARKE, R. F.
1950. Notes on the ornate box turtle. Herpetologica, 6(2):54.
1958. An ecological study of reptiles and amphibians in Osage
County, Kansas. Emporia St. Res. Stud., 7(1):52 pp.,
15 figs., 4 tables.
COWLES, R. B., and BOGERT, C. M.
1944. A preliminary study of the thermal requirements of desert
reptiles. Bull. Amer. Mus. Nat. Hist., 83(5):261-296,
figs. 1-3, pls. 19-29, 1 table.
CUNNINGHAM, B.
1939. Effect of temperature upon the developmental rate of the
embryo of the diamond back terrapin (_Malaclemys centrata_
Lat). Amer. Nat., 73:381-384.
DANINI, E. S.
1946. Histological processes as observed in the regeneration of
the carapace of the tortoise _Emys orbicularis_ L. Bull.
Acad. Sci. U. S. S. R., Biol., 5:581-594.
DERANIYAGALA, P. E. P.
1939. The tetrapod reptiles of Ceylon. Vol. 1, Testudinates and
Crocodilians. Columbo, ix-xxii + 412 pp., 137 figs.,
24 pls., 62 tables.
DITMARS, R. L.
1934. A review of the box turtles. Zoologica, 17(1):1-44, 41 figs.
DRIVER, E. C.
1946. Delayed hatching in the box turtle. Copeia, 1946(3):173-174.
EVANS, L. T.
1952. Endocrine relationships in turtles III. Some effects of male
hormone in turtles. Herpetologica, 8(2):11-14.
1953. The courtship pattern of the box turtle, _Terrapene c.
carolina_. Herpetologica, 9(4):189-192, 6 figs.
1954. Courtship and territorial behavior of lower vertebrates (A
review). Mimeographed, 50 pp.
EWING, H. E.
1939. Growth in the eastern box-turtle with special reference to
the dermal shields of the carapace. Copeia, 1939(2):87-92,
3 figs.
1943. Continued fertility in female box turtles following mating.
Copeia, 1943(2):112-114.
FINNERAN, L. C.
1948. Reptiles at Branford, Connecticut. Herpetologica,
4(4):123-126.
FITCH, H. S.
1952. The University of Kansas Natural History Reservation. Univ.
Kansas Mus. Nat. Hist., Misc. Publ., No. 4, 38 pp., 4 pls.,
3 figs.
1954. Life history and ecology of the five-lined skink, _Eumeces
fasciatus_. Univ. Kansas Publ., Mus. Nat. Hist.,
8(1):1-156, 2 pls., 26 figs, in text, 17 tables.
1955. Habits and adaptations of the Great Plains skink (_Eumeces
obsoletus_). Ecol. Monogr., 25:59-83, 11 figs., 10 tables.
1956a. An ecological study of the collared lizard (_Crotaphytus
collaris_). Univ. Kansas Publ., Mus. Nat. Hist.,
8(3):213-274, pls. 3-6, figs. 1-10, 9 tables.
1956b. Temperature responses in free-living amphibians and reptiles
of northeastern Kansas. Univ. Kansas Publ., Mus. Nat.
Hist., 8(7):417-476, 10 figs. in text, 6 tables.
1958. Home ranges, territories, and seasonal movements of
vertebrates of the University of Kansas Natural History
Reservation. Univ. Kansas Publ., Mus. Nat. Hist.,
11(3):63-326, 6 pls., 24 figs., 3 tables.
FORBES, T. R.
1940. A note on reptilian sex ratios. Copeia, 1940(2):132.
FOX, W.
1952. Seasonal variation in the male reproductive systems of
Pacific Coast garter snakes. Journ. Morph., 90(3):481-553,
5 pls., 13 figs., 3 tables.
1956. Seminal receptacles of snakes. Anat. Rec., 124(3):519-540,
3 pls., 1 table.
GEHLBACH, F. R.
1956. Annotated records of southwestern amphibians and reptiles.
Trans. Kansas Acad. Sci., 59(3):364-372.
GOULD, E.
1957. Orientation in box turtles, _Terrapene c. carolina_
(Linnaeus). Biol. Bull., 112(3):336-348, 5 figs.
GRANT, C.
1936. The southwestern desert tortoise _Gopherus agassizii_.
Zoologica, 21:225-229.
HAY, O. P.
1908a. Description of five species of North American fossil turtles,
four of which are new. Proc. U. S. Nat. Mus.,
35(1640):161-169, pls. 26-27, 3 figs.
1908b. The fossil turtles of North America. Carnegie Inst.
Washington, Publ. no. 75, iii-iv + 568 pp., 113 pls.,
704 figs.
HILDEBRAND, S. F., and PRYTHERCH, H. F.
1947. Diamond-back terrapin culture. U. S. Dept. Int., Fishery
leaflet no. 216, 3 pp., mimeographed.
HOFFMANN, C. K.
1890. Klassen und Ordnungen des Thier-Reichs. Bd. 6, Ab. 3,
Reptilien. I. Schildkröten. Winter, Leipzig, 442 pp.,
48 pls., 1 woodcut.
HUNT, T. J.
1957. Notes on diseases and mortality in Testudines. Herpetologica,
13(1):19-23, 1 table.
LATHAM, R.
1917. Studying the box turtle. Copeia, 1917(39):15-16.
LEGLER, J. M.
1954. Nesting habits of the western painted turtle, _Chrysemys
picta bellii_ (Gray). Herpetologica, 10(3):137-144.
1956. A simple and practical method of artificially incubating
reptile eggs. Herpetologica, 12(4):290.
1958. Extra-uterine migration of ova in turtles. Herpetologica,
14(1):49-52, 1 fig.
LEGLER, J. M., and FITCH, H. S.
1957. Observations on hibernation and nests of the collared lizard,
_Crotaphytus collaris_. Copeia, 1957(4):305-307, 1 pl.
LEWIS, T. H.
1950. The herpetofauna of the Tularosa Basin and Organ Mountains
of New Mexico with notes on some ecological features of
the Chihuahuan desert. Herpetologica, 6(1):1-10, 8 figs.
LINCOLN, F. C.
1930. Calculating waterfowl abundance on the basis of banding
returns. U. S. Dept. Agri., Circ. 118, 4 pp., 1 fig.,
2 tables.
LOOMIS, R. B.
1956. The chigger mites of Kansas (Acarina, Trombiculidae). Univ.
Kansas Sci. Bull., 37, pt. II, no. 19:1195-1443, 49 figs.,
29 maps, 3 tables.
LOVERIDGE, A., and WILLIAMS, E.
1957. Revision of the African tortoises and turtles of the suborder
Cryptodira. Bull. Mus. Comp. Zool., 115(6):165-557, 18 pls.,
62 figs., 10 tables.
LYNN, W. G., and ULLRICH, M. C.
1950. Experimental production of shell abnormalities in turtles.
Copeia, 1950(4):253-262, 2 pls., 2 figs.
MARR, J. C.
1944. Notes on amphibians and reptiles from the central United
States. Amer. Midl. Nat., 32(2):478-490, 1 table.
MATTOX, N. T.
1936. Annular rings in the long bones of turtles and their
correlation with size. Trans. Illinois State Acad. Sci.,
28:225-226.
MEDSGER, O. P.
1919. Notes on the first turtle I ever saw. (Abstract of a paper
presented Nov. 15, 1918) Copeia, 1919(69):29.
MCMULLEN, D. B.
1940. Cutaneous myiasis in a box turtle. Proc. Oklahoma Acad. Sci.,
20:23-25, 2 figs.
MILLER, L.
1955. Further observations on the desert tortoise, _Gopherus
agassizi_, of California. Copeia, 1955(2):113-118, 1 pl.,
2 figs., 2 tables.
MILLER, M. R.
1948. The seasonal histological changes occurring in the ovary,
corpus luteum, and testis of the viviparous lizard,
_Xantusia vigilis_. Univ. California Publ. Zool.,
47:197-224.
MITSUKURI, K.
1895. How many times does the snapping turtle lay eggs in one
season? Zool. Mag. Tokyo, 7 (85):143-147.
NEILL, W. T.
1948a. Hibernation habits of amphibians and reptiles in Richmond
County, Georgia. Herpetologica, 4(3):107-114.
1948b. Odor of young box turtles. Copeia, 1948(2):130.
NICHOLS, J. T.
1939a. Data on size, growth and age in the box turtle, _Terrapene
carolina_. Copeia, 1939(1):14-20, 2 figs., 2 tables.
1939b. Range and homing of individual box turtles. Copeia,
1939(3):125-127.
NORRIS, K. S., and ZWEIFEL, R. G.
1950. Observations on the habits of the ornate box turtle,
_Terrapene ornata_ (Agassiz). Nat. Hist. Misc., no. 58,
4 pp.
ODUM, E. P., and KUENZLER, E. J.
1955. Measurement of territory and home range size in birds. Auk,
72(2):128-137, 3 figs., 2 tables.
OLIVER, J. A.
1955. The natural history of North American amphibians and reptiles.
Van Nostrand, xi + 359 pp., 74 figs., 14 tables.
ORTENBURGER, A. I., and FREEMAN, B.
1930. Notes on some reptiles and amphibians from western Oklahoma.
Publ. Univ. Oklahoma Biol. Surv., 2(4):175-188, 2 maps.
PACKARD, R. L.
1956. The tree squirrels of Kansas. Univ. Kansas Mus. Nat. Hist.,
Misc. Publ., no. 11, 67 pp., 2 pls., 10 figs.
PENN, G. H., JR., and POTTHARST, K. E.
1940. The reproduction and dormancy of _Terrapene major_ in New
Orleans. Herpetologica, 2(2):25-29.
PETERS, J. A.
1948. The box turtle as a host for dipterous parasites. Amer. Midl.
Nat., 40(2):472-474.
RAINEY, D. G.
1953. Death of an ornate box turtle parasitized by dipterous larvae.
Herpetologica, 9(2):109.
RISLEY, P. L.
1933. Observations on the natural history of the common musk turtle,
_Sternotherus odoratus_ (Latreille). Pap. Michigan Acad.
Sci., Arts and Letters, 17:685-711, figs. 78-79, 1 table.
1938. Seasonal changes in the testis of the musk turtle,
_Sternotherus odoratus_ L. Journ. Morph., 63(2):301-317,
2 pls., 1 fig.
RODECK, H. G.
1949. Notes on box turtles in Colorado. Copeia, 1949(1):32-34.
ROKOSKY, E. J.
1948. A bot-fly parasitic in box turtles. Nat. Hist. Misc., no. 32,
2 pp.
SCHNECK, J.
1886. Longevity of turtles. Amer. Nat., 20(9):897.
SERGEEV, A.
1937. Some materials to the problem of the reptilian post-embryonic
growth. Zool. Journ. Moscow, 16:723-735.
1939. The body temperature of reptiles in natural surroundings.
Comptes Rendus (Doklady) de l'Acad. des Sci. de l'USSR,
22:49-52.
SMITH, H. M., and JAMES, L. F.
1958. The taxonomic significance of cloacal bursae in turtles.
Trans. Kansas Acad. Sci., 61(1):86-96.
SMITH, H. M., and RAMSEY, L. W.
1952. A new turtle from Texas. Wasmann Journ. Biol., 10(1):45-54,
1 pl., 1 table.
SMITH, R. C.
1954. An analysis of 100 years of grasshopper populations in Kansas
(1854-1954). Trans. Kansas Acad. Sci., 57(4):397-433,
1 pl., 5 figs.
STICKEL, L. F.
1950. Populations and home range relationships of the box turtle,
_Terrapene c. carolina_. Ecol. Monogr., 20:351-378,
15 figs., 5 tables.
STOCK, C., and BODE, F. D.
1936. The occurrence of flints and extinct animals in pluvial
deposits near Clovis, New Mexico. Part III,--Geology and
vertebrate paleontology of the late Quaternary near Clovis,
New Mexico. Acad. Nat. Sci. Philadelphia, 88:219-241,
pls. 5-10, 6 figs. in text.
STRECKER, J. K., JR.
1908. The reptiles and batrachians of McLennan County, Texas. Proc.
Biol. Soc. Washington, 21:69-84.
SURFACE, H. A.
1908. First report on the economic features of turtles of
Pennsylvania. Zool. Bull., Pennsylvania Dept. Agr.,
6(4-5):105-195, pls. 4-12, 16 figs., tables.
TAYLOR, W. E.
1895. The box tortoises of North America. Proc. U. S. Nat. Mus.,
17 (1019):573-588, 7 figs.
WEVER, E. G., and VERNON, J. A.
1956. Auditory responses in the common box turtle. Proc. Nat. Acad.
Sci., 42(12):962-965.
WILLIAMS, E.
1950. _Testudo cubensis_ and the evolution of western hemisphere
tortoises. Bull. Amer. Mus. Nat. Hist., 95(1):1-36,
pls. 1-8, 2 figs.
WOODBURY, A. M., and HARDY, R.
1948. Studies of the desert tortoise _Gopherus agassizii_. Ecol.
Monogr., 18:145-200, 25 figs., 4 tables.
_Transmitted August 27, 1959._
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15. The pigmy woodrat, Neotoma goldmani, its distribution
and systematic position. By Dennis G. Rainey and Rollin
H. Baker. Pp. 619-624, 2 figures in text. June 10,
1955.
Index. Pp. 625-651.
Vol. 8. 1. Life history and ecology of the five-lined skink, Eumeces
fasciatus. By Henry S. Fitch. Pp. 1-156, 26 figures in
text. September 1, 1954.
2. Myology and serology of the Avian Family Fringillidae,
a taxonomic study. By William B. Stallcup. Pp. 157-211,
23 figures in text, 4 tables. November 15, 1954.
3. An ecological study of the collared lizard (Crotaphytus
collaris). By Henry S. Fitch. Pp. 213-274, 10 figures
in text. February 10, 1956.
4. A field study of the Kansas ant-eating frog, Gastrophryne
olivacea. By Henry S. Fitch. Pp. 275-306, 9 figures in
text. February 10, 1956.
5. Check-list of the birds of Kansas. By Harrison B.
Tordoff. Pp. 307-359, 1 figure in text. March 10, 1956.
6. A population study of the prairie vole (Microtus
ochrogaster) in northeastern Kansas. By Edwin P.
Martin. Pp. 361-416, 19 figures in text. April 2, 1956.
7. Temperature responses in free-living amphibians and
reptiles of northeastern Kansas. By Henry S. Fitch.
Pp. 417-476, 10 figures in text, 6 tables.
June 1, 1956.
8. Food of the crow, Corvus brachyrhynchos Brehm, in
south-central Kansas. By Dwight Platt. Pp. 477-498,
4 tables. June 8, 1956.
9. Ecological observations on the woodrat, Neotoma
floridana. By Henry S. Fitch and Dennis G. Rainey.
Pp. 499-533, 3 figures in text. June 12, 1956.
10. Eastern woodrat, Neotoma floridana: Life history and
ecology. By Dennis G. Rainey. Pp. 535-646, 12 plates,
13 figures in text. August 15, 1956.
Index. Pp. 647-675.
Vol. 9. 1. Speciation of the wandering shrew. By James S. Findley.
Pp. 1-68, 18 figures in text. December 10, 1955.
2. Additional records and extensions of ranges of mammals
from Utah. By Stephen D. Durrant, M. Raymond Lee, and
Richard M. Hansen. Pp. 69-80. December 10, 1955.
3. A new long-eared myotis (Myotis evotis) from northeastern
Mexico. By Rollin H. Baker and Howard J. Stains.
Pp. 81-84. December 10, 1955.
4. Subspeciation in the meadow mouse, Microtus
pennsylvanicus, in Wyoming. By Sydney Anderson.
Pp. 85-104, 2 figures in text. May 10, 1956.
5. The condylarth genus Ellipsodon. By Robert W. Wilson.
Pp. 105-116, 6 figures in text. May 19, 1956.
6. Additional remains of the multituberculate genus
Eucosmodon. By Robert W. Wilson. Pp. 117-123,
10 figures in text. May 19, 1956.
7. Mammals of Coáhuila, Mexico. By Rollin H. Baker.
Pp. 125-335, 75 figures in text. June 15, 1956.
8. Comments on the taxonomic status of Apodemus peninsulae,
with description of a new subspecies from North China.
By J. Knox Jones, Jr. Pp. 337-346, 1 figure in text,
1 table. August 15, 1956.
9. Extensions of known ranges of Mexican bats. By Sydney
Anderson. Pp. 347-351. August 15, 1956.
10. A new bat (Genus Leptonycteris) from Coahuila. By Howard
J. Stains. Pp. 353-356. January 21, 1957.
11. A new species of pocket gopher (Genus Pappogeomys) from
Jalisco, Mexico. By Robert J. Russell. Pp. 357-361.
January 21, 1957.
12. Geographic variation in the pocket gopher, Thomomys
bottae, in Colorado. By Phillip M. Youngman.
Pp. 363-387, 7 figures in text. February 21, 1958.
13. New bog lemming (genus Synaptomys) from Nebraska.
By J. Knox Jones, Jr. Pp. 385-388. May 12, 1958.
14. Pleistocene bats from San Josecito Cave, Nuevo Leon,
Mexico. By J. Knox Jones, Jr. Pp. 389-396.
December 19, 1958.
15. New Subspecies of the rodent Baiomys from Central
America. By Robert L. Packard. Pp. 397-404.
December 19, 1958.
16. Mammals of the Grand Mesa, Colorado. By Sydney Anderson.
Pp. 405-414, 1 figure in text. May 20, 1959.
17. Distribution, variation, and relationships of the montane
vole, Microtus montanus. By Sydney Anderson.
Pp. 415-511. 12 figures in text, 2 tables.
August 1, 1959.
18. Conspecificity of two pocket mice, Perognathus goldmani
and P. artus. By E. Raymond Hall and Marilyn Bailey
Ogilvie. Pp. 513-518, 1 map. January 14, 1960.
19. Records of harvest mice, Reithrodontomys, from Central
America, with description of a new subspecies from
Nicaragua. By Sydney Anderson and J. Knox Jones, Jr.
Pp. 519-529. January 14, 1960.
20. Small carnivores from San Josecito Cave (Pleistocene),
Nuevo León, México. By E. Raymond Hall. Pp. 531-538,
1 figure in text. January 14, 1960.
21. Pleistocene pocket gophers from San Josecito Cave, Nuevo
León, México. By Robert J. Russell. Pp. 539-548,
1 figure in text. January 14, 1960.
22. Review of the insectivores of Korea. By J. Knox Jones,
Jr., and David H. Johnson. Pp. 549-578.
February 23, 1960.
More numbers will appear in volume 9.
Vol. 10. 1. Studies of birds killed in nocturnal migration.
By Harrison B. Tordoff and Robert M. Mengel, Pp. 1-44,
6 figures in text, 2 tables. September 12, 1956.
2. Comparative breeding behavior of Ammospiza caudacuta
and A. maritima. By Glen E. Woolfenden. Pp. 45-75,
6 plates, 1 figure. December 20, 1956.
3. The forest habitat of the University of Kansas Natural
History Reservation. By Henry S. Fitch and Ronald R.
McGregor. Pp. 77-127, 2 plates, 7 figures in text,
4 tables. December 31, 1956.
4. Aspects of reproduction and development in the prairie
vole (Miorotus ochrogaster). By Henry S. Fitch.
Pp. 129-161, 8 figures in text, 4 tables.
December 19, 1957.
5. Birds found on the Arctic slope of northern Alaska.
By James W. Bee. Pp. 163-211, pls. 9-10, 1 figure in
text. March 12, 1958.
6. The wood rats of Colorado: distribution and ecology.
By Robert B. Finley, Jr. Pp. 213-552, 34 plates,
8 figures in text, 35 tables. November 7, 1958.
7. Home ranges and movements of the eastern cottontail in
Kansas. By Donald W. Janes. Pp. 553-572, 4 plates,
3 figures in text. May 4, 1959.
8. Natural history of the salamander, Aneides hardyi.
By Richard F. Johnston and Schad Gerhard. Pp. 573-585.
October 8, 1959.
More numbers will appear in volume 10.
Vol. 11. 1. The systematic status of the colubrid snake, Leptodeira
discolor Günther. By William E. Duellman. Pp. 1-9,
4 figs. July 14, 1958.
2. Natural history of the six-lined racerunner,
Cnemidophorus sexlineatus. By Henry S. Fitch.
Pp. 11-62, 9 figs., 9 tables. September 19, 1958.
3. Home ranges, territories, and seasonal movements of
vertebrates of the Natural History Reservation.
By Henry S. Fitch. Pp. 63-326, 6 plates, 24 figures
in text, 3 tables. December 12, 1958.
4. A new snake of the genus Geophis from Chihuahua, Mexico.
By John M. Legler. Pp. 327-334, 2 figures in text.
January 28, 1959.
5. A new tortoise, genus Gopherus, from north-central
Mexico. By John M. Legler. Pp. 335-343.
April 24, 1959.
6. Fishes of Chautauqua, Cowley and Elk counties, Kansas.
By Artie L. Metcalf. Pp. 345-400, 2 plates, 2 figures
in text, 10 tables. May 6, 1959.
7. Fishes of the Big Blue River Basin, Kansas. By W. L.
Minakley. Pp. 401-442, 2 plates, 4 figures in text,
5 tables. May 8, 1959.
8. Birds from Coahuila, Mexico. By Emil K. Urban.
Pp. 443-516. August 1, 1959.
9. Description of a new softshell turtle from the
southeastern United States. By Robert G. Webb.
Pp. 517-525, 2 pls., 1 figure in text. August 14, 1959.
10. Natural history of the ornate box turtle, Terrapene
ornata ornata Agassiz. By John M. Legler. Pp. 527-669,
16 pls., 29 figures in text. March 7, 1960.
Index will follow.
Vol. 12. 1. Functional morphology of three bats: Eumops, Myotis,
Macrotus. By Terry A. Vaughan. Pp. 1-153, 4 plates,
24 figures in text. July 8, 1959.
2. The ancestry of modern Amphibia: a review of the
evidence. By Theodore H. Eaton, Jr. Pp. 155-180,
10 figures in text. July 10, 1959.
3. The baculum in microtine rodents. By Sydney Anderson.
Pp. 181-216, 49 figures in text. February 19, 1960.
More numbers will appear in volume 12.
Transcriber's Notes
Except for the typographical corrections listed below, the following
changes were made. The section label (Color and Markings) on page 593
was changed from italics as those were used to delimit the subsections.
Based on the formatting used for other text in this publication, other
minor typographica changes may also have been made where periods,
commas, etc. were left out or inserted erroneously.
Typographical Corrections
Page Correction
==== =========================
542 Plate 1 â Plate 15
568 hiberation â hibernation
580 expresssed â expressed
582 rail â rain
590 spical â apical
597 Pl. 11 â Plate 19
601 mullberry â mulberry
603 an â and
604 monentarily â momentarily
614 detph â depth
640 presssure â pressure
667 retpiles â reptiles
Text Emphasis
_Text_ - Italics
=Text= - Bold + Italics
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