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Group Title: Natural history of the Alabama map turtle, Graptemys pulchra Baur, in Alabama (FLMNH Bulletin v.21, no.2)
Title: The Natural history of the Alabama map turtle, Graptemys pulchra Baur, in Alabama
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00095835/00001
 Material Information
Title: The Natural history of the Alabama map turtle, Graptemys pulchra Baur, in Alabama
Series Title: Bulletin of the Florida State Museum Biological sciences
Physical Description: p. 47-111 : ill. ; 23 cm.
Language: English
Creator: Shealy, Robert M
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1976
Copyright Date: 1976
Subject: Alabama map turtle   ( lcsh )
Reptiles -- Alabama   ( lcsh )
Genre: bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Bibliography: p. 110-111.
General Note: Cover title.
Statement of Responsibility: Robert M. Shealy.
 Record Information
Bibliographic ID: UF00095835
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 03656095
lccn - 77622059


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Table of Contents
    Front Cover
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Full Text

of the
Biological Sciences

Volume 21 1976 Number 2





are published at irregular intervals. Volumes contain about 300 pages and are not necessarily
completed in any one calendar year.

RHODA J. RYBAK, Managing Editor

Consultants for this issue:


Communications concerning purchase or exchange of the publications and all manuscripts
should be addressed to the Managing Editor of the Bulletin, Florida State Museum, Museum
Road, University of Florida, Gainesville, Florida 32611.

Publication date: December 30, 1976

This public document was promulgated at an annual cost of $2,067.54
or $2.068 per copy. It makes available to libraries, scholars, and all in-
terested persons the results of researches in the natural sciences, em-
phasizing the Circum-Caribbean region.

Price: $2.10



SYNOPSIS: From June 1969 until October 1972 the natural history of the Alabama map turtle,
Graptemys pulchra, was studied in southern Alabama. Over 500 specimens were collected, of
which 286 were measured, marked, and released, and 91 were autopsied for reproduction and
food studies.
Graptemys pulchra was the most abundant turtle in the study area and its primary food item,
the imported oriental mussel Corbicula maniliensis, was the most abundant macro-invertebrate.
Large, mature individuals of G. pulchra were more abundant than juveniles.
Home range was apparently more stable in males, but only females exhibited homing be-
havior. I found that females either returned to the home area or remained at the displacement
site. Those returning to their original localities moved distances of 24 river channel km (15 mi)
or more up- and downstream.
Growth is rapid in juveniles but declines sharply at maturity and approaches zero shortly
after maturity. Males reach sexual maturity in their third or fourth year, but females apparently
do not reach maturity until they are approximately 14 years old. Maximum size in females is
reached in about 23 years, and natural longevity probably exceeds 50 years.
Sexual dimorphism with respect to size is pronounced, the largest male studied being about
half the carapace length of the smallest female (120 mm vs 212 mm).
Although sperm were present in the male reproductive tract throughout the year, mating
behavior was observed only in autumn months, suggesting that sperm is stored in females. The
male courtship sequence is similar to that described for other aquatic emydines, except that
the "titillation tool" of the male is the snout, rather than elongate fore-claws. Elongate fore-
claws are not characteristic of adult males.
Predation probably resulted in the destruction of 95 percent of the natural nests during
the study period, although some reproductive seasons were much more successful than others.
The major diurnal predator on nests was the fish crow, and the major nocturnal predator was
the raccoon. The only significant enemies of adults are man and possibly the alligator snapping
turtle, Macroclemys temmincki.
Reproductive potential varied from 7 to 71, depending on the size of the female, and aver-
aged 29 eggs per season per female. An average of 4 (1-6) clutches were laid per season per fe-
male. Extra-uterine migration of ova was usual.

'The author is Associate Professor of Biology at Pensacola Junior College, Pensacola, Florida 32504. He completed most of this
research in conjunction with his doctoral dissertation while at Auburn University, Auburn, Alabama. Manuscript accepted
15 April 1975.

SHEALY, ROBERT M. 1976. The Natural History of the Alabama Map Turtle, Graptemys pulchra
Bauer, in Alabama. Bull, Florida State Mus., Biol. Sci. 21(2):47-111.


Nests were located 1-20 m from the water's edge, usually on large, exposed sandbars. Coarse-
ness of the sand seemed to be the major criterion on which nest site selection was based.
Incubation required from 74 to 79 days at 290C, the average nest chamber temperature in
natural nests. Infertility of individual eggs and entire clutches was common.
Males and females under 100 mm carapace length were primarily insectivorous, whereas
juvenile and adult females in the study area subsisted almost entirely on Corbicula. Feeding
generally began in May and ended in October. Since growth ceased in early September, food
assimilated during September and October was probably stored for winter.
The most significant determinant of seasonal activity was water temperature. Activity and
feeding decreased sharply at water temperatures below 190C (660F). Complete inactivity (hiber-
nation) of the entire population during the winter was not observed. No significant interspecific
competition with other turtle species was found.


IN T R O D U C T IO N ................ ........ ........................... ... ................ ................ .. .. ....... ...... ........ 4 9
A C KN O W LED G EM ENT S .. ... ..... .................................................................................................... 54
M E T H O D S ......................... .. .................................................... ................................................. .. 5 4
D ISTRIBUTION AND V ARIATION .... ............................................................................................... 56
G R O W T H .............................................................................................................. 6 0
O ntogenetic G row th ........................................... ...... ............................................. 60
Seasonal G row th .... ................................................................................ ............... 62
Longe vity and Senility ........ ................................................................................................... 6
Longevity and Senility .................. 67
R E P R O D U C T IO N .............................. ........................................................................ ....... ..... 6 9
M aturity and Sexual D im orphism ...................................................................... ............. 69
Reproductive Cycles ................................. ............................. 71
Reproductive Potential and Eggs .................. ...................................................... 73
Mating ............................................................ 74
Sperm Storage .......................................... ..................................... 75
N e stin g ................................. ... ... ............................................. ......... 7 7
In cu b action .................. .... ....................... .......................... ...................... 80
H a tc h in g .............................. ............................ ............. ....................... .............................. 8 3
H atchlings ...................................... ................................. ............................... .. 86
P O PU LAT IO N D YN A M IC S ................................................................................................................ 86
P opu lation D ensity ....................................................... ................................................. 86
C o m p o sitio n ......................... .. ................................ ....... ................... .......... ........... 8 7
Mortality ......................... ......................... 90
Post-natal M ortality....................... ......................................................... 90
Hom e Range and H om ing ................................................................... ......... 91
F OO D AN D F EED ING ................... ............................................................................................. 94
AcTIvrrITY ............................................................................ ................... 99
Se aso n a l A c tiv ity .............................................................................. ........................ .... .. 9 9
D ie l A c tiv ity ....... ................................... .......................... ......................... .................. .... 10 1
PREDATORS AND PARASITES ...................................................................................................... 104
P re d a tio n ............................................................. ............................ 10 4
P arasites .................................. ............ ....... ...................................... 10 8
INTERSPECIFIC INTERACTIONS ................................ ................................................................ 108
L IM ITING F ACTORS .............................. ............ .............................................. ......... ........ 109
L ITERATURE C ITED .... .............................. ...... .......................... .............. ............ 110



The genus Graptemys is confined to eastern North America and includes
nine species of strongly aquatic turtles. It belongs to the family Emydidae,
a nearly cosmopolitan and mostly aquatic group. Graptemys pulchra was
described by Baur in 1893 from a lake near Montgomery, Alabama.
From June 1969 until October 1972 studies were conducted on the natural
history of the Alabama map turtle, Graptemys pulchra in Alabama. Emphasis
was placed on field observations of behavior, studies of movements, and
growth (using mark and release techniques), and on laboratory studies of the
reproductive cycle and food habits. Over 500 specimens were collected, of
which 91 were autopsied and 286 were measured, marked, and released.
The population selected for most intensive study inhabits a 30-mile seg-
ment of the Conecuh River, Escambia County, extreme southern Alabama
(87000'W, 31005'N; R11E, T1N). The upstream limit of the study area
was the U. S. highway 29 bridge (McGowan's Bridge). Downstream, the limit
was state highway 41 at East Brewton, Alabama. The segment is bisected by
Escambia County road 4, approximately 13 km due east of East Brewton. Col-
lections were confined to the 24 km of channel between U.S. 29 and county
road 4 and to a kilometer stretch immediately downstream from state road 41.
No collections or observations were made between Escambia 4 and Ala-
bama 41.
The 8 km of river channel immediately downstream from U.S. 29 is com-
paratively straight, with very few large, exposed sandbars (Fig. 1). The banks
consist mostly of exposed limestone and stabilized sand deposits, with over-
hanging hardwood canopy. The banks erode very slowly, probably because
of the limestone bed. Thus, few trees are undercut to be added to the supply
of natural basking sites and hiding places. The channel in this area consists
of straight stretches up to 2 km long with water 2 to 3 m in depth, alternating
with occasional holes up to 10 m deep (during low water). The bottom sub-
strate is quite stable and consists of coarse sand, bare limestone, or occasion-
ally silt and detritus.
Exposed limestone diminishes and large bare sandbars are increasingly
frequent downstream from this area. Long straight stretches are infrequent,
and sinuous undulations of the unstable channel result in a nearly continuous
alternating series of sandbars (Fig. 2). The channel in these areas is charac-
teristically shallow (1 m) between sandbars but deep (3 to 8 m) and narrow
(5 to 10 m) opposite the sandbars. Banks across from the sandbars are rapidly
undercut (up to 6 m per year), and the channel is often choked with fallen
trees. Such places offer ideal sites for basking turtles and underwater hiding
places for many aquatic vertebrates. The associated unstable and bare sand-
bars are preferred nesting sites for Graptemys pulchra, Trionyx spinifer, and
T. muticus. During low water levels, the current velocity is approximately




Figure 1. The Conecuh River near U. S. Highway 29, Escambia County, Alabama. Left,
downstream view in April; Right, aerial view.


~crLi` .ti. 1 'LI"
li~cl J
""' L ~ '-~
Ec. -q .~
--i -

Figure 2. The Conecuh River near Escambia County Highway 4, Alabama. Upper, large sandbar used extensively by nesting Graptemys
pulchra from May to July, 1971 (see Fig. 20). Fallen trees offer preferred basking sites over areas of deep water. The only alligator encountered
during the study was observed on the bottom near the undercut bank. Lower, aerial view.


dI~ ":



3 kmph in straight stretches and in shallow areas between sandbars and 1
kmph in, deep areas across from sandbars. During periods of high water,
current velocity is 1-6 kmph in all areas. The water level at East Brewton
fluctuates about 5 m seasonally. At Century, Florida, a 30-year record of
Escambia River discharges shows a variation from a low of 596 cfs (cubic feet/
second) to a high of 77,200 cfs (mean = 5,460 cfs), according to U.S. Geological
Survey records.
Several major studies of the natural history of emydine turtles have ap-
peared during the past 22 years. Pseudemys scripta, a widely distributed and
very generalized emydine, has been subjected to the most intensive studies,
including both North Temperate and Tropical zone populations (Cagle 1950,
Moll and Legler 1971). Legler (1960) studied the natural history of Terrapene
ornata, a terrestrial emydine, in detail. Studies by Cagle (1954), Gibbons
(1968), Sexton (1959, 1965), Ernst (1971), Christiansen and Moll (1973), and
Moll (1973) provide a thorough natural history of Chrysenmys picta.
Published information on species of the genus Graptemys consists mostly
of general notes on behavior and ecology. The most detailed accounts are
found in Webb's (1961) work on G. pseudogeographica ouachitensis and
Cahn's (1937) observations on G. geographic and G. pseudogeographica. The
apparent dissimilarities in ecology and life histories between these species
and G. pulchra make these observations of little value in the interpretation
of the natural history of G. pulchra.
Information on C. pulchra in the literature is likewise scant, consisting
mostly of brief notes on basking behavior (Boyer 1965) and food preferences
(Conant 1958). The most significant treatment of reproduction and growth is
found in Cagle's (1952) work comparing G. pulchra with G. barbouri.

For assistance in the field I am indebted to Thomas W. Foster, Edward P. Simonds, and Kelly
Thomas. For advice and encouragement during the study, I wish to thank George W. Folkerts
and James L. Dobie. Others who contributed their time and services include William T.
Washington, Hiram Smith, Earl Berry, Kirby L. Hays, John D. Freeman, James Lazear, and
my wife, Arla W. Shealy. For financial support I am grateful to the Department of Zoology-
Entomology, Agricultural Experiment Station, Auburn University. I am especially indebted to
my major professor, Robert H. Mount, for his encouragement during the study and for many
valuable suggestions in the preparation of the manuscript.


Two collecting techniques were used. When water clarity permitted, collecting was done
with a mask and snorkel. During periods of high and turbid water this was accomplished by drift-
ing downstream with only the collector's head exposed, netting turtles as they basked. Both tech-
niques varied greatly in effectiveness, yielding from 0-30 specimens/hr. Generally, diving
yielded mostly large mature individuals and few juveniles, whereas surface netting yielded a
greater diversity of sizes. Night collecting, both by diving and by surface efforts, was attempted
on several occasions but was unsuccessful. Submerged baited traps and basking traps used early
in the study were also unsuccessful.

Vol. 21, No. 2


Behavior was studied during the nesting season from tree platforms or from banks across
from nesting beaches. Field behavioral observations made at other times of the year were inci-
dental to the regular collecting. However, turtles were also regularly observed in laboratory
tanks and outdoor pools.
Measurements were taken on all specimens that were marked and released, autopsied, or
preserved. Linear measurements to the nearest millimeter were made with a vernier or outside
caliper. Measurements include carapace length (CL) (the distance from the anterior edge of
the carapace to the posterior edge of the carapace), plastron length (PL) (the distance from the
most proximal point of the anterior plastral notch to the most proximal point of the posterior
notch), width (measured at the widest point of the carapace, usually at the level of the fifth or
sixth marginal scutes), and height (the distance from the anterior edge of the second central
scute to the nearest ventral point on the plastron). In males pre-anal tail length was measured
from the posterior edge of the plastron to the anterior border of the vent. In females skull width
was measured at the widest point. In some females the average length of the pectoral scutes at
the medial seam was measured with calipers, and the total length of the medial seam was mea-
sured with a curvimeter. Weight was determined to the nearest gram for some individuals by
means of a triple-beam balance.
Inter-annulus width, defined as the distance between annuli (growth rings) on the frontal
plane of the femoral scutes, was measured to the nearest millimeter with vernier calipers (Fig. 3);
this measurement was taken near the middle of the medial seam of the femoral scute. Normally,
all visible inter-annulus widths were measured, as was the band in process of formation. Annulus
lengths were not used because of the difficulty in discerning ends of the annuli. The abdominal
scute was not used because it exhibited greater erosion and loss of annuli.


Figure 3. Ventral view of the posterior half of a plastron of Graptemys pulchra from the
Conecuh River, Escambia County, Alabama, showing annuli on femoral scutes. Inter-annulus
width "a" shows growth since the previous winter. Width "b" shows growth during the previous


Routine field data included determinations of air and water temperatures with an alcohol
thermometer, notes on water level and clarity, and weather conditions. Observations associated
with nests encountered in the field included chamber temperature, distance from the water,
elevation above the water, and substrate qualities.
Specimens that were captured and released were marked by notching the marginal scutes,
using the following numbering system: units (1 to 9) were assigned to the right marginals 2
through 10, tens (10 to 90) to left marginals 2 through 10, number 100 to the first left marginal,
and number 200 to the first right marginal. Thus, number 263, for example, would have notches
on the first right marginal, seventh left marginal, and the fourth right marginal. Notches normally
were clearly visible three years after release, even in rapidly growing individuals (Fig. 4).
In order to determine reproductive condition, food items, and parasites, autopsies were made
at monthly intervals (weekly during critical months). Reproductive and digestive organs were
removed from larger individuals through the inguinal pocket in order to avoid disrupting the
Ova were measured at their greatest diameter and oviducal eggs at their greatest length and
width. The number of corpora lutea was recorded when present. Testes were measured to the
nearest millimeter at their greatest and smallest diameters and the values averaged. Notes were
taken on the condition of the males' epididymides and on sperm presence and condition.
Intestinal food items and fecal samples were analyzed. The latter were collected by placing
individuals in separate containers having sufficient water to cover the carapace, where they
were retained from 2 to 4 days. The water was then decanted, and identifiable material picked
out and preserved in 70% ethyl alcohol.
Eggs collected from oviducts or natural nests were incubated by one of two methods. One
method involved placing the eggs in a plastic bag along with a paper towel saturated with water,
sealing the bag, and storing it in a constant temperature chamber at temperatures close to those
of natural nests (280-30C). No eggs hatched using this method, and all developed heavy fungal
infestations. A second method utilized gallon containers or cinder blocks filled with clean,
moist sand similar to that of natural nests. The eggs were buried in the sand at depths of from
10 to 15 mm. Some containers were kept indoors and others outdoors, under both shaded and
sun-lighted conditions. Hatching success was high using this method.


Graptemys pulchra is found in major drainage systems entering the Gulf
of Mexico from the Pearl River in Louisiana and Mississippi to the Yellow
River in Florida and Alabama (Conant 1958) (Fig. 5). It occurs in the Pasca-
goula, Mobile, and Escambia systems but is absent from the smaller Perdido,
Blackwater, and Escatawpa drainages (the last river actually flows into the
lowermost part of the Pascagoula system).
Ecologically, the species shows fairly broad requirements, occurring in all
sizeable streams within its range that support reasonably large populations
of aquatic molluscs. The heaviest populations in Alabama, and presumably
elsewhere, are found in large Coastal Plain streams. The species is strongly
aquatic, and specimens have never been seen on land except while basking
under stress or nesting.
Although primarily a stream form, the species has evidently held its own
in artificial impoundments, such as the Gantt Reservoir at Andalusia, Ala-
bama. The species was originally described from two specimens captured in
a "lake" near Montgomery, Alabama (Baur 1893). This lake was probably
either an artificial impoundment or an oxbow of the Alabama River, since

Vol. 21, No. 2


Figure 4. Marked specimens of Graptemys pulchra from the Conecuh River near East Brew-
ton, Alabama, four years after release. Above, old female, tenth marginal notched. Below, young
male, seventh marginal notched. On rapidly growing individuals, notches tend to be obscured
within a few years after release. (Specimens photographed on mirror surface).


....... .....




Figure 5. Geographical distribution of Graptemys pulchra. Known area of occurrence is indicated by stippling. z
Unknown areas are indicated by question marks. Major drainages, from west to east, include: Pearl River, Pascagoula
River, Mobile Bay, and Escambia-Yellow Rivers.


G. pulchra has not been observed in any other type of lake. The comparative
degree of success of the species in lentic versus lotic situations has not been
The species comprises at least four geographical variants: one in the Pearl
River drainage, a second in the Pascagoula drainage, a third in the Mobile
Bay drainage, and a fourth in the Escambia and Yellow River drainages. Shell
proportions separate members of the Mobile Bay drainage from all others, the
adults having proportionately much flatter shells than adults from other
drainages (Fig. 6). The adaptive significance of this shape is unknown, but
may possibly be linked with adaptations to greater turbulence of streams
above the Fall Line. The Mobile Bay drainage has the most extensive drain-
age area above the Fall Line of all the systems in which G. pulchra occurs.
Gene flow from such a large area of selective pressure could account for the
flattened body form in Coastal Plain individuals within the drainage.

Figure 6. Geographical variation in Graptemys pulchra in Alabama. The individual at left
shows flattening of the shell characteristic of Mobile Bay drainage specimens. The individual at
right shows higher shell characteristic of the Escambia-Yellow River drainage form. Carapace
lengths are similar.

The Pascagoula form has more light pigmentation on the head and cara-
pace marginals than does the Escambia River form. Also, a grayish hue tints
the basic green ground color in the Pascagoula form.
Specimens from the Pearl River appear to be intermediate in coloration
between the Pascagoula and Escambia River forms, although resembling the
Escambia River form more closely. Cagle (1952) remarked that females from
the Pearl River differ from those of the Escambia River in that "the markings
of the lower jaw tend to be broken into erratic lines that constitute a longi-
tudinal pattern in some and a transverse one in others." Tinkle (1961) showed
that, with respect to laminal seam arrangements, specimens from the Pearl
River more closely resemble those from the Escambia River than from the
Pascagoula River. Variation among the forms also occurs with respect to
other head patterns, plastral and carapacial markings, and shell width to
length ratios. The extent and consistency of such differences, however, are yet
to be evaluated. An intensive study of variation between populations in the
four drainages will probably reveal distinctiveness requiring several sub-
specific designations.





Data on growth were derived in part from 257 individuals that were
captured, marked, and released in the Conecuh River between U.S. 29 and
East Brewton from August 1969 to September 1971. Between May 1970 and
October 1972, 59 were recaptured. To distinguish slight growth increments
and to minimize the effects of measurement error, the product of length,
width, and height measurements was used as a size index. Cessation of growth
during winter months was discounted by using only the number of months
of growth (from inter-annulus data) between release and recapture. Growth
rate was variable among females (Fig. 7). If rates among size classes are aver-
aged, however, a significant trend may be seen. The first level includes fe-
males of less than 160 mm carapace length. Although molluscivorous (see
pp. 94-95), this group fed only on smaller bivalves, which were observed to
be much scarcer and much more seasonal in abundance than larger ones.
Thus, limited food resources may have resulted in less than maximal growth.




60 *

0 03544
Z 0-
o 3 *
20. *


60 80 100 120 140 160 180 200 220 240 260 280
Figure 7. Growth in juvenile and female Graptemys pulchra from the Conecuh River,
Escambia County, Alabama, based on release and recapture data. Numbers are averages over
the ranges indicated. Size=carapace length X width X height X 10-' (mm). Only months in
which growth occurred were counted.


The second level includes individuals from 160 to 220 mm in length. Members
of this size class comprise sub-adults and young adults which were able to
utilize a nearly "unlimited" bivalve resource and thus to show maximum
growth. Growth surges at puberty have been observed in Pseudemys rubri-
ventris, and hypothetically correlated with dietary shift (Graham 1971).
Patterson and Brattstrom (1972) found growth surges in the desert tortoise,
Gopherus agassizi.
The third and lowest level includes large females which are also able to
utilize the bivalve resource, but presumably because of redirection of energy
to reproductive output show a minimal growth rate. Moll and Legler (1971)
attributed cessation of growth in adult P. scripta to redirection of energy to-
ward gametogenesis.
Growth in mature males (Fig. 8) showed a marked decline after maturity.
This is consistent with data illustrated in Figure 25, showing that there was
less variation in size among mature males than among mature females. The
existence of selective forces in this direction is probable, but the cause and
mechanism of such selection is not apparent.
Using space between annual growth rings annulii) as indicators of growth
rate essentially confirms the above interpretations of growth in both males
and females. The last complete inter-annulus width as a function of carapace




I 4-

0 2- 0
0 *

70 80 90 100 110 120
Figure 8. Growth in adult male Graptemys pulchra from the Conecuh River, Escambia
County, Alabama, based on release and recapture data. Size carapace length X width X height
X 10-' (mm). Only months during which growth occurred were counted.


length in the lower Conecuh River population is described in Figures 9 and
10. Among females, a fairly stable growth rate is evident between 45 mm and
160 mm CL, followed by a peak just prior to maturation (160 to 220 mm) and
a sharp decline approaching zero among large individuals (Fig. 9). There is
a stable growth rate in juvenile males, which is followed by a sharp decline
after maturation and slowing markedly in large individuals (Fig. 10).


E 6-

#* * ^
Z* *
*2-- ,* *
1A00 6 .0.0


40 80 120 160 200 240 280
Figure 9. Growth in juvenile and female Graptemys pulchra from the Conecuh River, Es-
cambia County, Alabama, based on measurements of last inter-annulus widths.


Determination of seasonal growth was made by correlating date of cap-
ture with the ratio of new growth (last inter-annulus width) to the preceding
year's growth (next to last inter-annulus width). An evident trend can be seen
in Figure 11, although the results were highly variable, presumably because
of "false annuli." The earliest distinguishable growth appeared in May and
was probably roughly linear until August, when it averaged 67% of that of
the preceding year. After August growth declined sharply, reaching an aver-
age of 76% by October.
Studies of fecal samples showed feeding began in April and ended in
October. Theoretically, then, growth would be 100% at least by October.
Much of the discrepancy between this and the observed rate of 76% was al-




Z O2-




O0 0

S% Gomm 0-a

20 40 60 80 100 120 140

Figure 10. Growth in male Graptemys pulchra from the Conecuh River, Escambia County,
Alabama, based on measurements of last inter-annulus widths.

o oe Ce voe *

* S r *.

S *%" *:*



Figure 11. Seasonal growth in Graptemys pulchra from the Conecuh River, Escambia
County, Alabama, based on last inter-annulus width expressed as a percentage of the next-to-last
inter-annulus width (last complete width).



most certainly due to "false annuli," which resulted from temporary cessa-
tion of growth not associated with winter inactivity. Environmental upsets,
such as periods of extremely high water, have been shown to result in the for-
mation of such "false annuli." Moll and Legler (1971) found that minor
growth rings may form in two days and major ones in five days, presumably
because of cessation of feeding. Specimens of G. pulchra collected during
periods of high water levels, however, showed no reduction in fecal volume.
Since two or more such annuli may be formed in a single growing season, their
inclusion in the data may have significantly depressed estimates of growth,
especially in the later months. It is probable that growth essentially ceased
in September.
The cause of the decline in growth between August and October is not
apparent. Redirection of energy from growth to fat storage, preparatory to
overwintering, was postulated by Sexton (1965). It has been demonstrated,
however, that preparation for winter in C. pseudogeographica consists of stor-
age of liver glycogen rather than fat (Emerson 1967). In female G. pulchra,
accelerated follicular development occurs from September to November and
undoubtedly requires considerable food reserves, as Moll and Legler (1971)
found for P. scripta.
Estimates of age were based on measurements of annual growth (inter-
annulus width) on the femoral scutes, which were correlated with width of
the scutes. Essentially the same technique has been used for determining age,
at least in the first few seasons of growth, in C. picta (Sexton 1959a), P. scripta
(Moll and Legler 1971), P. rubriventris (Graham 1971), Terrapene ornata
(Legler 1960), G. pseudogeographica (Webb 1961), and Gopherus agassizi
(Patterson and Brattstrom 1972). Measurements of annual increases in fem-
oral width of recaptured specimens served to validate inter-annulus measure-
ments. The high variability of growth after maturation confined reliable es-
timates of age to immature individuals. In females at maturation (220 mm) the
average femoral width was 103 mm, whereas in hatchlings the average width
was 20 mm. The difference between the two figures indicates a growth in-
crease of 83 mm since hatching. This figure, when divided by the average
annual increase in femoral width among immature females (6 mm), results
in an average of 14 growth seasons between hatching and maturity. In nine re-
captured, immature females the average increase in femoral width per year
was 6 mm, confirming the inter-annulus average used. These findings contrast
with those of Moll and Legler (1971) for P. scripta in Panama, in which females
matured in 5 to 7 years. The tropical climate probably allowed a longer
growth season and shorter juvenile life in this form. Legler (1960) calculated a
juvenile period of 10 to 11 years for female T. ornata, and Graham (1971)
demonstrated an 11-year juvenile period for female P. rubriventris.

Vol. 21, No. 2


In males at maturation the average femoral width (80 mm carapace
length) was 38 mm, an increase of 18 mm from hatching. Inter-annulus mea-
surements showed an average annual increase of 6 mm in femoral width in
both immature males and females (Table 1). Therefore, an average of three
years elapses between hatching and maturity in males. This figure agrees with
Moll and Legler's (1971) findings for male P. scripta (2 to 4 years), and with
Webb's (1961) observation of G. pseudogeographica (2 +years). Cagle (1952)
described a small mature male G. pulchra from the Pearl River in its fourth
season of growth. Many mature, or nearly mature males, with three or four
annuli were observed in the Conecuh River population.


C.L. F.W. Inc. F.W. A Inc. F.W. Years N

40-220 20-103 83 6.0 14.0 14
220-240 103-111 8 4.6 1.7 6
240-270 111-124 13 1.8 7.2 23
Total 22.9
40-80 20-38 18 6.0 3.0 2
80-90 38-42 4 3.3 1.2 4
90-110 42-50 8 1.9 4.2 21
Total 8.4

"Abbreviations: C. L.carapace length in millimeters; F. W.-combined width of femoral scutes at the carapace length
interval; Inc. F. W.-increase in femoral width over the interval; A Inc. F. W. average annual increase in femoral width;
Years- number of years required to traverse the interval; N -number of individuals in each group.

As previously indicated, post-maturation growth is highly variable in both
sexes but rapidly approaches zero in large individuals (Fig. 7). Estimates of
average numbers of years required to traverse three size intervals, based
on interannulus measurements, are given in Table 1. From these estimates,
it can be seen that maximum size is attained in an average of 23 years in fe-
males and 8.4 years in males. Above these levels, there is no discernible corre-
lation between age and size.
On the basis of skull width, ages of old adult females may also be esti-
mated. If the maximum skull width observed (65 mm) is used as an intercept
with the CL-skull width regression line for females under 240 mm long (Fig.
12), proportional growth would result in a CL of 330 mm at 65 mm skull
width. An individual of this CL would have a femoral width of approxi-
mately 151 mm, or 40 mm over that of the width after 15.7 years. Assuming
a stable femoral width increase of 4.6 mm per year (Table 1), 8.7 years would



Y =2.46 0.19X
70- r 0.95


Figure 12. Skull width as a function of carapace length in female Graptemys pulchra from
the Conecuh River, Escambia County, Alabama. Regression line, equation, and correlation co-
efficient (r) derived from individuals less than 240 mm in carapace length.

be required to reach this size, for a total of 24.4 years. This figure agrees
rather closely with the estimate of 23 years based on shell growth.
That considerable variability exists is well illustrated by an exceptional
female that showed all signs of advanced age, i.e. shortened pectoral scutes,
extensively wandering plastral sutures, and loss of head pigmentation. The
size (220 mm CL), however, corresponded to that of a female in her first re-
productive season.
The extent of allometric growth in skull width in females is shown in
Figure 12. There is a relatively close correlation between CL and skull width
at carapace lengths under 240 mm, but this declines sharply at lengths over
240 mm. Above this size, all points are found on the positive side of a regres-
sion line derived from skull measurements of immature females. This indi-
cates not only a high degree of variation in the size at which growth stops but
also a persistence of growth in skull width independent of body growth.
In very old females, extensive wandering of plastral seams occurs, often
resulting in the formation of small additional scutes near the midline. Also,
differential growth among plastral scutes results in reduction of some scutes
and expansion of others. The length of the pectoral scute relative to the PL
decreases with increased medial seam length (Fig. 13). The close correlation
between pectoral scute reduction and medial seam length in older females
may indicate that both measures are equally affected by age. An increase in
length of the humeral scute is apparently associated with the decrease in
pectoral scute length.
Such a relationship is not shown between medial seam length and skull
Such a relationship is not shown between medial seam length and skull

Vol. 21, No. 2



Q_ .150-

I .140-
0 *
z 0
_* * *
< .120-

S: .110

.100- **


1.00 1.02 1.04 1.06 1.08 1.10 1.12 1.14 1.16 1.18
Figure 13. Pectoral scute length relative to plastron length (PL) as a function of medial seam
length (MSL) relative to plastron length in adult female Graptemys pulchra from the Conecuh
River, Escambia County, Alabama.

width (Fig. 14), except in young feamles (skull width less than 52 mm). This
close correlation decreases with age, indicating a sharp decline in skull
growth, if not complete cessation. It is probable that those individuals having
enlarged skulls and slight wandering of seams were still growing.
In Figure 15 a similar, though less pronounced, condition in males with
respect to pre-anal length can be seen. Again, there is a pronounced decrease
in correlation after maturity, and the pre-anal length of nearly all large males
lies above the regression line derived from measurements of immature indi-


Estimates of longevity cannot be based on body size, since growth essen-
tially stops at a relatively early age. Since skull width also fails to increase
in very old individuals, its use is also limited. G. pulchra probably attains ages
far beyond the above estimates, but estimates of advanced ages are restricted
to much more comparative and qualitative approaches. Legler (1960) and
Cagle (1950) estimated natural longevity in Terrapene ornata and P. scripta,







S *
** S


- *
S SS m


* *

44 46 48 50 52 54 56 58 60

62 64 66

Figure 14. Medial seam length (MSL) relative to plastron length (PL) as a function of skull
width in adult female Graptemys pulchra from the Conecuh River, Escambia County, Alabama.


5 30-

z 20-

Y =-21.61 + 0.47 X

r =0.80

* -

70 80 90 100 110 120
Figure 15. Pre-anal tail length as a function of carapace length in male Graptemys pulchra
from the Conecuh River, Escambia County, Alabama. Regression line, equation, and correla-
tion coefficient (r) derived from individuals less than 85 mm carapace length.


Vol. 21, No. 2


respectively, to be in excess of 50 years. Longevity in G. pulchra is probably
Indicators of old age in emydines have been described by Moll and Legler
(1971) and Cagle (1950, 1952). In P. scripta, "continued molting without
growth produces the progressively shallower interlaminal seams and the
fusions of scutes ... (Moll and Legler 1971). Cagle (1952) observed that very
old G. barbouri showed an increase in black pigmentation, irregular plastral
sutures, and a thickening and erosion of the shell. Indicators of advanced age
in G. pulchra include: wandering plastral seams, decrease in pectoral scute
length with associated increase in humeral scute length, loss of contrast in
head pigmentation, and a disproportionate increase in skull width of females
and pre-anal length of males.
No specimens with "senile" gonads (degenerate ovaries or testes) were
found during this study. However, a few individuals of both sexes, showing
signs of advanced age, were apparently waning in vigor. Areas of erosion
were evident in the shell and alveolar surfaces of the jaws. Efforts to escape
seemed to be less vigorous and a generally emaciated appearance was shown.
These individuals, although evidently senile somatically, apparently had nor-
mal reproductive organs. Probably such individuals died before reproduction
was impaired, or their lack of vigor was due to some factor other than age.

Sexual maturity in male Graptemys pulchra was determined by the pres-
cence of sperm in the epididymides. The smallest mature male autopsied
was 80 mm CL and 16 mm pre-anal tail length. Studies of growth reveal that
this size may have been attained within 3 or 4 years after hatching (Table 1).
Cagle (1952) reported male G. pulchra from the Pearl River having plastron
lengths of from 89 to 117 mm, which would correspond to carapace lengths
of 110 to 145 mm. In all probability the measurements he recorded as plas-
tron lengths were actually carapace lengths.
Sexual maturity in females, as determined by the presence of corpora
lutea or ovarian follicles over 15 mm in diameter, is achieved at a size of about
220 mm CL and 43 mm skull width. Based on growth studies, it is estimated
that this size may be attained in an average of 14 years (Table 1). Although
all follicles over 10 mm in diameter in mature females are ovulated, adoles-
cent females may develop follicles in the 10-15 mm size range one year prior
to their first ovulation.
Size at maturity among females is somewhat variable. The largest imma-
ture female was 220 mm CL, whereas the smallest mature female was 212
mm long. Cagle (1952) reported that the smallest mature female he studied


had a plastron length of 170 mm, which would correspond to a carapace
length of 210 mm, using proportions from the Conecuh River population.
Variation in size at maturity was also noted in Chelonia mydas by Carr and
Goodman (1970), who stated that "some mature at small and others at large
sizes; and that once they are mature, i.e., once they have made their first trip
to the nesting beach, their growth becomes negligible..."
The sexes differ greatly in overall size, pre-anal length, skull width, food
habits, and to a lesser degree in body pigmentation and behavior.
Size is by far the most distinguishing character in adults. The largest male
recorded had a CL slightly more than half that of the smallest mature female
(120 mm and 212 mm, respectively). Mature males ranged from 80 mm to 120
mm CL, whereas mature females ranged from 212 mm to 285 mm in length.
Pre-anal tail length is noticeably greater in males as early as the third sea-
son of growth, at which time the vent extends beyond the rear edge of the
carapace. Increase in pre-anal length continues after growth of other body
proportions effectively ceases (Fig. 15), and thus serves as an indicator of ad-
vanced age in older specimens.
Relative skull width is noticeably greater in females than in males after
the first few years of growth and, as in male pre-anal length, continues to in-
crease after body growth ceases (Fig. 12). This character is closely linked to
differences in food habits. Females in the first few years and males of all ages
are primarily insectivorous, and older juvenile and adult females are almost
entirely molluscivorous (Fig. 27). The enlarged jaws and correspondingly
widened head is clearly an adaptation for crushing molluscs, as observed by
Carr (1952) and Conant (1958).
Other observed differences between the sexes are more subtle. Differences
in behavior include a somewhat greater reluctance of males to abandon bask-
ing sites. This may be linked to the fact that males, which are much smaller
than females, are much less conspicuous to enemies. Since the only significant
enemy of adults probably is man, the reduced conspicuousness serves to offer
a smaller and less noticeable target to "plinkers" (shooters of nearly any wild-
life or inanimate target that presents itself). The conspicuousness of adult fe-
males, on the other hand, has probably resulted in selective pressure favoring
greater wariness.
Red pigment occurs occasionally on the heads of adult males, but not in
adult females. The red blends with the usual yellow, resulting in an orange
coloration. Individuals with orange head patterns were found among hatch-
lings, very young females, and approximately 10 percent of the adult males.
Shells of adult males are also noticeably thinner and more fragile than those
of females of similar size.
Very slight differences between the sexes were observed in their micro-
habitat preferences. Males, although commonly found among concentrations
of females, were also found in all-male aggregations, usually in areas of rela-

Vol. 21, No. 2


tively shallow water. Such areas were avoided by adult females during the
day. All-female aggregations were also commonly found. On several occasions
over 30 mature females were taken from an area without encountering a
single male. During daily periods of submersion and apparent inactivity,
males were more commonly found among roots and limbs of fallen trees, and
females were usually seen resting against the bottom beneath these objects.


MALE.-Active sperm were present in the epididymides of mature males
throughout the year, indicating that mating may occur at any time. Times
of mating and seasonal variation in male fertility were not determined.
The few instances of courtship activity that were observed occurred
from September to November. Testis size was greatest in September (Fig.
16) and was coincidental with greatest follicular development in females.
The male reproductive cycle, therefore, may be centered around an autumn
mating season, during which sperm are stored by the female until the follow-
ing nesting season. This pattern may be followed in neotropical Pseudemys
scripta (Moll and Legler 1971), but is not followed by some other emydines.
Graptemys pseudogeographica mates in April and possibly also in the fall
(Carr 1952). Terrapene ornata also exhibits a spring and autumn mating
period (Legler 1960), as does P. scripta in the Temperate Zone (Cagle 1950).


E 12-
E *

LU 10.

Figure 16. Monthly variation in tests diameter in male Graptemys pulchra from the Cone-
cuh River, Escambia County, Alabama.
IL 6- C


Figure 16. Monthly variation in testis diameter in male Graptemys pulchra from the Cone-
cuh River, Escambia County, Alabama.


FEMALE-AS shown in Figure 17, from May to September there was a re-
duction in the enlarged follicles (over 10 mm diameter), expressed as a per-
centage of reproductive potential or maximum number of eggs produced in
a season, found in Conecuh River specimens of Graptemys pulchra. The num-
ber of eggs is complementary; i.e. if 30 percent of the reproductive potential
in a given month were in the form of enlarged follicles, then 70 percent would
be expressed as egg production up to that time.
The female reproductive cycle consists of oviposition and follicular
growth from May to August and rapid follicular growth from September to
November, during which time feeding and activity ceases. A very similar pat-
tern was reported for P. scripta (Moll and Legler 1971), Terrapene ornata
(Legler 1960), and Chrysemys picta (Moll 1973, Christiansen and Moll 1973).
The failure of the described line to reach zero during August, after which
no nests or oviducal eggs were found, implies that some follicles were not
ovulated. Atretic follicles were not common and accounted for no more than
5 percent of the reproductive potential. Atresia is also unimportant in T. or-
nata (Legler 1960), as is probably true for most emydines (Moll and Legler
1971). The fate of remaining follicles is unknown but they probably are ovu-
lated very late in the season or represent follicles developing early in prepa-
ration for the following nesting season.


80- **

LU 0
O *'*
UJ (


Figure 17. Monthly variation in numbers of enlarged follicles (over 10 mm diameter) ex-
pressed as percentages of observed or calculated reproductive potentials (from Fig. 18) in adult
female Graptemys pulchra from the Conecuh River, Escambia County, Alabama.

Vol. 21, No. 2


Reproductive potential as used here is defined as the maximum number
of eggs that may be produced in a season by a single female. Since very few
follicles over 10 mm in diameter were present at the end of the reproduc-
tive season (August), I assume that most follicles over 10 mm in diameter at
the beginning of the season developed and were ovulated during the season.
Determination of reproductive potential for each female was made by count-
ing all follicles over 10 mm in diameter and adding the number of corpora
lutea, if present. This method was applicable only until July, at which time
the possibility of corpora lutea regression could lead to erroneous estimates.
Figure 18 shows that although reproductive potential is variable, it is ob-
viously correlated with CL (r = 0.79). Associated with increased reproductive
potential in larger females is an increase in clutch size (Fig. 19) and possibly
also the number of clutches. The most important effect, however, is the ex-
tension of the nesting season. Large females are thus the first and last to nest
during a particular season. The average reproductive potential among 31
autopsied females was 29. The smallest potential observed (7) was in a small
female probably in one of her first reproductive seasons. The largest potential
(71) was in the largest specimen captured during the study (285 mm CL,
AUM # 21970). Whether 71 eggs would have been produced is questionable,
but 33 corpora lutea were present at the time of autopsy (July 4). Since ovi-

Y = 124.95 + 0.63X
r =0.79

* 60-

40- .-


210 220 230 240 250 260 270 280
Figure 18. Reproductive potential (number of corpora lutea plus enlarged follicles) as a
function of carapace length in adult female Graptemys pulchra from the Conecuh River, Es-
cambia County, Alabama. All determinations were made from March through June.










Figure 19. Clutch size as a function of carapace length in adult female Graptemys pulchra
from the Conecuh River, Escambia County, Alabama.

position was observed throughout July and the period of oviposition was
extended in larger females, it is probable that most of the remaining follicles
(38) would have been ovulated. In G. barbouri, Cagle (1952) found reproduc-
tive potentials of from 11 to 51 (average 17). He excluded the "unusually
high" 51 in his average. His largest G. barbouri (300 mm CL) had a reproduc-
tive potential of 51, and my largest Conecuh River G. pulchra (285 mm) had a
potential of 71. This implies that G. pulchra has a significantly greater repro-
ductive potential than G. barbouri.

I only saw courtship and mating a few times and never a single complete
sequence, from initiation of courtship to copulation. Sperm was found to be
present in the male tract at all seasons, thus implying year-round mating po-
tential. In both the laboratory and the field, however, mating activity was
observed only from September to November. The following account is based
on several brief field and laboratory observations, and one may assume that
it characterizes the overall sequence of events:
With neck extended, the male would directly approach the cloacal region
of the female, who apparently indicated by scent her identity or receptive-

*0 0



Vol. 21, No. 2


ness. He then swam in front of his potential mate and assumed a face-to-face
position in one of several attitudes: slightly to either side, slightly above, or
slightly below the female's head. He then rapidly vibrated his head vertically
against the side of the female's snout, alternating sides approximately every
five seconds. The duration of this phase of courtship was not determined;
however, based on several observations this could be as short as 15 seconds.
During this display the female apparently withdrew her head slightly, with
the eyes partially closed. The male then swam directly to the cloacal region
of the female and attempted to appose the cloacae by looping his tail beneath
the tail of the female, while maintaining a position on the rear of her carapace.
The angle formed between the axes of the shells was approximately 450
Often the male seemed to "sense" a lack of receptiveness in the female at this
stage and returned to the head-to-head posture, possibly repeating the head-
to-tail sequence several times before successful copulation. This repetition
was observed only in captive specimens, and it may be that stresses of captivity
inhibited the females' normal response. In nature, a single courtship se-
quence may normally be sufficient. Only brief attempts at copulation were
observed, and only in the laboratory. Duration of copulation was not deter-
mined. This courtship pattern resembles closely that of some other aquatic
emydines, including P. scripta (Jackson and Davis 1972). The major differ-
ence lies in the "titilation sequence," in which the snout of the male G. pul-
chra is vibrated rather than the claws of the forelegs, as in Pseudemys spp.
Graptemys kohni and G. flavimaculata, however, have been observed to use
claws in courtship (Cagle 1955), and elongate foreclaws are characteristic
of mature G. pseudogeographica males (Webb 1961).

If mating occurs chiefly, or entirely, in the fall, then sperm must be stored
in the female reproductive tracts, since no ovulation occurs until late April.
Oviducal scrapings in March and May contained active and inactive sperm.
Sperm storage has been reported in Malaclemys terrapin (Hildebrand 1932),
T. ornata (Legler 1960), and T. carolina (Ewing 1943). No concerted effort
was made to study sperm storage, since mating may have occurred at any time
during the periods of activity and possibly even during the winter months.
From autopsied females I took 104 oviducal eggs that averaged 38 mm by
26 mm in size; 34 eggs from nests averaged 38 mm by 27 mm. This slight dif-
ference in width resulted from rapid water absorption, even though the nests
were usually less than three days old when found. During incubation, also, the
greatest increase was in width, resulting in a more nearly spherical shape at
hatching. Cagle (1952) measured five eggs from the oviducts of a female from
the Escambia River. Their average measurements (39 mm by 24 mm) fell
well within the range of variation observed. On the other hand, his measure-



ments of eggs from a Pearl River female (45 mm by 26 mm) are well outside
the range of variation in the eggs of Conecuh River G. pulchra. The leathery
shell of the egg is of a finely granular texture at oviposition but becomes
smoother soon after laying, as water is absorbed and turgor increases.
Ovulation begins in late April and continues through July (Fig. 17). The
earliest oviducal eggs were found on April 28 and the latest on July 30. The
peak of nesting activity in the study area occurs in June, corresponding to a
sharp decline in numbers of enlarged follicles in autopsied females (Fig. 17).
Table 2 shows individual average monthly follicle numbers in three size
ranges during the ovulatory season. Since reproductive potential is directly re-
lated to body size, both the average carapace length of autopsied females and
the calculated reproductive potentials are included in the table. If the total
number of enlarged follicles present during each month is subtracted from the
estimated reproductive potential, an estimate of the number of ova ovulated
prior to autopsy may be obtained. Twenty-five clutches averaged 7.2 eggs per
clutch and the average reproductive potential was 29; thus, the average esti-
mated number of clutches would be approximately 4, as confirmed in Table 2.
Estimates of numbers of ova ovulated prior to autopsy correspond roughly to
one clutch per month from May through July.


Size May June July August

20-25 13(9-18) 12(4-20) 4(0-5) 1(0-3)
15-20 6(3-8) 5(2-9) 3(0-13) 4(0-7)
10-15 5(2-6) 5(1-6) 2(0-2) 1(0-3)
Total 24 22 9 6

CL 244 254 249 250
RP 30 36 33 33
Ovulated 6 14 24 27
N 8 6 8 5
'Abbreviations: Size-average follicle diameter in mm (range in parentheses); CL-average carapace length in mm; RP-
reproductive potential as estimated from the regression line of Fig. 18; Ovulated-estimated number of follicles ovulated prior
to autopsy; N number of females autopsied. The average reproductive potential was 29.3, average clutch size was 7.2, and the
average number of clutches per female per year was 4.0.

The number of clutches obviously is correlated directly with size, as is re-
productive potential, and autopsies and nesting signs indicate that large fe-
males also ovulate earlier and later in the nesting season than small females. A
single clutch or two small clutches is characteristic of females in their first re-
productive season. At the other extreme, probably six or seven clutches
would be laid by the largest female examined, having a reproductive po-
tential of 71 and a single clutch size of 12. However, my findings suggest little

Vol. 21, No. 2


correlation between body size and clutch size (Fig. 19), and if such is the case
up to 10 clutches (7 eggs per clutch) might have been laid by this female in a
single season. Moll and Legler (1971) reported six clutches for P. scripta, the
greatest number known for an emydine.
Nearly all follicles over 10 mm in diameter at the beginning of the nesting
season were ovulated, and there was no evidence that new enlarged follicles
developed during the nesting season. Many, if not all, of the follicles present in
late August were in the early stages of development, preparatory to the subse-
quent nesting season. Although a few may have become atretic, they would
not have represented more than 5 percent of the reproductive potential.
Extra-uterine migration of ova has been observed in several species of tur-
tles (Legler 1960) and is probably a phenomenon of general occurrence. Such
migration had occurred in at least 67 percent of the female G. pulchra autop-
sied, as determined by lack of correspondence between numbers of corpora
lutea and oviducal eggs in respective ovary-oviduct units.
Shelled eggs have been reported in the body cavity of Deirochelys reticu-
laria but apparently produced no harmful effects (Cagle and Tihen 1948). In
June, 1971, a large female G. pulchra was captured, marked, released after
being in captivity for over a week, and recovered at the release site several
weeks later. It made no attempt to escape, even though approached directly
while basking, and was obviously in very poor condition. Subsequent autopsy
revealed the presence of a shelled egg in the coelom. The shell of this egg was
heavily calcified, as were the shells of the nine eggs in the oviducts. The liver
and mesenteries were mottled with yellow, implying widespread infection.
Whether the condition arose because egg laying could not take place during
captivity is uncertain, but if this were the case, many other marked and re-
leased females could have been similarly affected during the study.

Field observations of nesting coincided closely with the season of ovula-
tion, as determined by autopsy. The earliest nests and oviducal eggs were
found in late April and the latest in late July. Tracks were often seen on nesting
beaches well before the nesting season. The purpose of such pre-nesting ex-
plorations is unknown, but they probably serve to determine the suitability of
potential sites. Because of the unpredictable nature of sand deposition during
high water, beaches are subject to wide fluctuation in quality from year to
Nesting site situations were variable, but most commonly were on large
sandbars associated with sharp bends in the river (Fig. 2). Others were found
among areas of moderate undergrowth and heavy canopy along relatively
straight river sections (Fig. 1). In order of decreasing importance, factors in-
fluencing suitability of nesting sites appeared to be: sand particle size, eleva-



tion above the water level, cover quality, and distance from the water's edge.
The characteristic most consistently associated with nesting sites was very fine
sand. All normal and complete nests were found in such a substrate. This sand
is easily excavated without settling, forms a firm crust when wetted and dried,
and retains moisture beneath this crust even when exposed to prolonged dry
periods. In a few exceptional cases, nests were found in coarser sand that of-
fered none of these qualities. Such nests were usually incomplete and con-
tained only one or two eggs. Apparently the coarse sand substrate was resorted
to by the female only after a thorough exploration of the beach failed to reveal
a suitable site or after she had repeatedly failed to scale heavy slopes of
coarse sand leading to more favorable sites (Fig. 20). Such "desperation nest-
ing" seemed to be associated with small females, judging from the size of the
Females rarely wandered far from the water when nesting. Nests were gen-
erally situated 3-15 m from the water's edge. This is in contrast to many other
aquatic emydines, such as Pseudemys scripta and Graptemys geographic. The
former may move up to half a kilometer overland while nesting (Cagle 1950,
Moll and Legler 1971), and the latter also wanders long distances inland in
search of nesting sites (Carr 1952).
Assuming suitable substrate, nests were located fairly consistently at eleva-
tions of 2-3 m above the existing water level. On gently sloping banks, such
elevations were sometimes reached only after a trip of up to 70 m from the
water's edge. The greatest distance traveled was 150 m, over apparently suit-
able substrates. No nest, or even "test holes" were dug along the way, even
though the nesting season was at its peak.
A complete nesting sequence was not observed during the study. Six frag-
mentary observations, when considered together, provided a reasonably com-
plete picture of nesting behavior. Three observations were made at the Cone-
cuh River study area and three at Opintlocco Creek, a small stream in the
Mobile Bay drainage in Macon County, Alabama. The earliest observation
was made at 7:00 a.m. CST and the latest and 8:00 p.m. CST. Two others
were made in the morning, one at noon, and the sixth at 4:00 p.m. Various
conditions of cloud cover were present, but at no time was it raining. Tem-
peratures were variable, primarily because of the different times during
which observations were made. It seems that nesting may occur at any time,
subject to local variations in predator and human activity.
The following account of nesting behavior is a composite of the six frag-
mentary observations. The female, with head elevated, lingered at the water's
edge for several minutes, during which time she surveyed the area by rotating
her head approximately 450 to each side, pausing about 15 seconds at each
point of maximum rotation. With head lowered and extended, she then left the
water and ambled at a seemingly invariable and mechanical pace (about one

Vol. 21, No. 2

.,W ,W- -
- -J~- i -r

pi- Y .. --; 'C-
'Sa -. UXi



I.. -,

I .w

Figure 20. Sandbar heavily used in 1971 by nesting female Graptemys pulchra (see Fig. 2), Conecuh River, Escambia County, Alabama.
Note trail in the foreground with shallow "test holes." Apparent difficulty in scaling sandy slope is shown by horizontal and back-sliding trails at
center. All nests were located on the upper level and many were at the edges of vegetation (background).

~ir~!'~.'~P~i~,L~[ ~YI-~SiPl~e~
=f.r a'--
~r jc,
-re -d
c~""~' ~h
~r~w 1

,, ~p~


step per second) directly onto the sandbar. Occasionally she would pause and
raise her head, perhaps to look for possible predators, or perhaps to search for
a suitable nest site. Otherwise she appeared oblivious to potential terrestrial
On one occasion a large female was easily captured within 2 m of the
water during such a nesting journey. She made no attempt to enter the water,
but withdrew her head and legs into the shell. Another time a female, sur-
prised at night approximately 2 m from the water, made a frenzied dash for
the water, barely being overtaken at its edge.
Between pauses, the head was kept lowered. Periodically, the nose was
pressed close to the substrate, as if seeking olfactory clues. At variable intervals
the consistency of the sand was tested with the front legs by an alternating
sweeping motion, creating furrows from 1 to 5 cm deep. Occasionally, deep
holes were dug, apparently with the hind legs, but were not completed (Fig.
21). Such "test holes" were often found to have stones, leaf litter, roots, or
other obstacles at the bottom. When the site was selected, excavation was
carried out by alternating sweeps and scrapes of the hind legs. The resulting
nest was a flask-shaped cavity about 15 cm deep, having a lower spherical
chamber about 10 cm in diameter and a neck about 4 cm in diameter. The
eggs were seemingly deposited with no regard to position and covered com-
pletely by alternating sweeping movements of the hind legs. No "plug" was
formed, as in Pseudemys spp. As sand was drawn into the nest, each leg was
forced into the entrance to pack its contribution to the filling, this continuing
until the cavity was filled. This was followed by lateral movements of the body
that served to smooth the sand over the nest entrance. The route leading to the
nesting site could have been quite tortuous, whereas that leading back to the
water was invariably direct (Fig. 21). The behavior observed by Cahn (1937) in
G. pseudogeographica, in which the nesting female described a complete cir-
cle during oviposition, was not evident in G. pulchra.
Artificial nests were maintained as closely as possible to field conditions,
being constructed of concrete blocks filled with sand and placed outdoors
where they received approximately a half day of sunlight and a half day of
shade. Temperatures were also maintained close to those of natural nests.
Sand from a natural nest site, or a similar site, was used as the nest medium.
Incubation periods ranged from 74 to 79 days (av. 76) in nine artificial
nests. This compares reasonably with 65 to 80 days in Chrysemys picta (Ernst
1971), 61 to 79 days in Pseudemys scripta in the Temperate Zone, and 71 to
83 days in neotropical P. scripta (Moll and Legler 1971). Field observations
showed an average period of 95 days (79 to 110) between the peak of nesting
and the peak of emergence. These observations were considered much less
reliable than those based on artificial nests as indicators of incubation period.

Vol. 21, No. 2





Figure 21. "Test hole" dug by nesting female Graptemys pulchra at the Conecuh River,
Escambia County, Alabama. Note narrow groove made by the tail between footprints, dis-
tinguishing G. pulchra tracks from those of Trionyx spp., which makes broad tail grooves.



Inasmuch as most nests were destroyed by predators, observations of hatching
or hatchlings were scarce. Also, hatchlings remained in the shells within the
nest until yolk absorption was complete, requiring at least several additional
Eight determinations of nest temperatures were made in the field, ranging
from 23 to 310C (av. 290C). The lowest temperature observed was in a nest
located in a shallow depression in complete shade, whereas the highest was
in a comparatively shallow exposed nest in sand darkened slightly by humus.
Egg mortality apparently exceeded 90 percent in each of the three nesting
seasons during the study period. Such mortalities have also been observed in P.
scripta (Moll and Legler 1971), T. orata (Legler 1960), and C. picta (Ernst
1971). Cagle (1950) found only one undisturbed nest out of 500 on a nesting
bank in Louisiana.
Mortality may have been somewhat less during the 1970 nesting season
than in the following two seasons, as evidenced by the relatively large number
of hatchlings appearing in the fall of 1970. Nest predation near areas of human
population, such as East Brewton, seemed to be less than in more remote areas.
In the Conecuh River study area, only 10 intact nests were found during three
nesting seasons, whereas several hundred destroyed nests were found in the
same period. All of the intact nests were fresh, and it is unlikely that they
would have escaped predation. The fish crow was the major diurnal egg pred-
ator and the raccoon the major nocturnal predator.
Although the effects of egg submersion was not studied, it was observed
that at least some nests survived following periods of temporary inundation.
During the 1972 season one nest, from which at least six hatchling G. pulchra
had emerged, had been beneath the water line for a week or more during early
Several cases of presumed infertility were found, both in individual eggs
and in entire clutches. Infertility appeared to be more common in populations
from small Mobile Bay drainage streams in Macon County (Cubahatchee
Creek, Opintlocco Creek) than in the Conecuh River population. Since popu-
lation density was much lower in these smaller streams, it is possible that the
greater frequency of infertility resulted from less opportunity for successful
mating. Of 64 eggs from the Conecuh River population incubated in 1972, one
entire clutch (8 eggs) and one egg from another clutch failed to develop. One
entire clutch of ten eggs at Cubahatchee Creek was apparently infertile. Sev-
eral other clutches incubated in 1969 and 1970 from these Mobile Bay drain-
age streams contained eggs that were undeveloped or entirely inviable.
An unidentified fungus, which was found only on the surface of infertile
eggs, was initially blamed for much egg mortality. No embryo was found in
any egg supporting fungal growth. To determine if fertile eggs were suscepti-
ble, eggs from several clutches were placed in sand where an entire clutch had
been infested by fungus. No fungal growth on the eggs was evident after two

Vol. 21, No. 2


months, even though the sand was heavily infiltrated with hyphae. One egg
was found to lack an embryo and the yolk was dehydrated, presumably re-
sulting from an earlier rupture of the shell. All other eggs hatched normally.
Soon after deposition the eggs increased rapidly in size and turgidity, pre-
sumably as a result of water absorption. One clutch of eggs averaged 29.5 mm
by 43 mm just prior to hatching, as compared to the average of 26 mm by 38
mm for all measured eggs at oviposition. Water absorption by eggs of T. or-
nata was reported by Cunningham and Hurwitz (1936). Pores have also been
shown to be present in the shell of emydine turtle eggs (Young 1950).
During incubation, the upper half of the egg shell changes from translu-
scent pink to white within a few days after laying. The lower half of the
shell remains pink nearly until hatching. The white area indicates the posi-
tion of the dorsal surface of the developing embryo and, if the egg is undis-
turbed, the hatchling is in an upright position at hatching.
Normally the hatchling is in an upright position within the egg, with
the long axis of the body corresponding to the greatest length of the egg.
Hatching begins with a minute puncture of the shell in the head region,
which probably occurs as a result of penetration by the caruncle. The hole,
(Fig. 22A) is located at, or slightly dorsal to, the apex of the egg. Amniotic
fluid flows freely out of the puncture, causing rapid collapse of the shell.
Within 15 to 30 minutes a vertical or horizontal enlargement of the punc-
ture results in one or several straight slits about one cm in length (Fig. 22B).
This is followed by a crossing of slits, often in an asterisk pattern, forming an
opening through which the head can be extended. Rupture of the shell and
pulmonary respiration before yolk absorption is perhaps made necessary by
a decreased allantoic capacity for adequate gas exchange. Lynn and von-
Brand (1945) demonstrated that late turtle embryos require as much oxygen
as hatchlings, and that turtles in the process of hatching require more.
Exposed hatchlings remain in the shell about four days, during which time
the remaining yolk is resorbed. The yolk sac decreases in size from 12 to 15
mm at hatching to nearly complete absorption after three days (Fig. 22E).
In natural nests, greater lengths of time may be spent within the shell, pre-
sumably delaying emergence until conditions are more favorable. Thus, nests
left undisturbed often contained hatchlings with all yolk absorbed and with
tightly closed and healed umbilical scars. In artificially exposed hatchlings,
yolk absorption and umbilical scar formation occurred within 5 to 8 days.
The caruncle (Fig. 22F) is shed generally within two weeks after hatching.
No signs of hatchlings overwintering in the nest were observed. This is
in contrast to the findings of Cagle (1944b) for P. scripta; Ernst (1971), Sex-
ton (1957), and Hartweg (1946) for C. picta; and Newman (1906) for some
other species of Graptemys. All hatchlings found in the spring had heavily



Figure 22. Representative stages in hatching in Graptemys pulchra from the Conecuh River,
Escambia County, Alabama. The initial puncture made by the caruncle is enlarged to an asterisk-
shaped opening. The head and forelegs enlarge the opening further and emergence is normally
arrested at this stage for the several days required for yolk absorption.

Vol. 21, No. 2



stained plastra, indicating prolonged exposure to a muddy substrate. No nest
was found in such a substrate, but bottoms in slow-moving river sections pre-
ferred by hatchlings were usually composed chiefly of fine silt. Also, no hatch-
ling tracks were seen on nesting beaches in the spring.
Movement to the water by hatchlings was consistently direct. This is in
contrast to the behavior of Trionyx hatchlings, which left the nest in appar-
ently random directions, some traveling a hundred meters to reach water that
was less than 10 m away and visible from the nest.

Fecal samples from newly hatched G. pulchra indicate that they begin
feeding shortly after reaching the water. The tendency to bask is apparently
greater in hatchlings than in older individuals. Often only hatchlings or year-
lings were found basking during comparatively unfavorable weather condi-
tions in the fall. They also displayed a greater reluctance to enter the water
and could often be directly approached and captured with no regard for cover
on the part of the captor. A greater need for pre-hibernal growth or food
storage may have prompted such activity. Hatchlings were found to feed as
late as November, while older individuals generally stopped feeding in Octo-
Mortality of hatchlings after entering the water was apparently low, be-
cause yearlings seemed to be as numerous in the spring as hatchlings were
the preceding fall. Fecal samples from several specimens of a large aquatic
predator, the alligator snapping turtle Macroclemys temmincki, caught in the
study area, showed only mussel remains. No stomach samples were taken
from other potential predators, the most important of which may be several
species of gar and the Great Blue Heron. Although a single alligator (Alligator
mississippiensis) was observed, it was not considered to be a significant pre-
dator of G. pulchra in the study area.

The highly variable and discontinuous distribution of individuals along
most sections of river in the study area made estimates of population density
difficult to substantiate. Use of a "Lincoln Index" under these circumstances
greatly overestimated population size. For example, use of an unmodified
index would result in an estimated density of over 500 individuals of Grapt-
emys pulchra along the 500-meter segment of river immediately downstream
from the East Brewton bridge, assuming unbiased sampling. Such estimates
are highly untenable; therefore direct observations and collecting data were
relied upon for more reasonable estimates of population density.
Two methods of estimating population density were used. For long,

Vol. 21, No. 2


straight stretches of river with a relatively homogeneous bottom, counts of
basking individuals were made during periods of maximum basking (high
water levels). On winding segments of river, consisting of shallow runs with
gravel bottoms alternating with deep silted or sandy pools, individuals usually
concentrated in the pools during periods of low water level. Diving under
these conditions often yielded large numbers of individuals, even though
small sizes often were not well represented. The scarcity of smaller sized indi-
viduals may have been due to differences in feeding habits (see pp. 94-99).
The numbers of individuals in such concentrations at favorable sites, when
expressed as a function of the distance between such sites, resulted (with some
modification) in a more or less workable estimate of population density.
Population estimates using both methods are listed in Table 3. I believe
that in both cases true numbers are underestimated significantly, and at best
probably represent no more than 75 percent of the true density. The density
of G. pulchra in the study area was estimated to be approximately one turtle
per 3-4 m of river length. Other estimates of population density in aquatic
emydine turtles are one adult Pseudemys scripta per 6 m of river (Moll and
Legler 1971), one P. scripta per 3.3 m of river (Tinkle 1958), and 239 Chry-
semys picta per acre (Ernst 1971).


Location U. S. 29 Co. #4 E. Brewton
Date April-May, 1970 September, 1970 September, 1969
Method Surface Diving Diving
Juveniles 16 0 18
female, immature 10 23 14
female, mature 5 8 17
male, mature 4 15 16
Total 35 46 65
Area 500 m 300m 500 m
Number per 7 15 13
100 m
Validity 25% 50% 50%
Balanced 28 30 26
per 100 m

*Area is in meters of river channel (longitudinal). Validity is the estimated percentage of turtles counted by the method
used. Balanced estimate is the observed density plus the estimated number of turtles not counted by the method used.

Frequency of size classes is illustrated in Figures 23 to 25. Among females
(Fig. 23) and juveniles, pronounced peaks are evident for size classes 50 to
75 mm CL and 225 to 250 mm. The first peak includes both males and females


during at least the first two years of growth. Development of sexual maturity
in males over 75 mm eliminates them from remaining classes, thus accentu-
ating the decline in numbers to the 75 to 100 mm class. A further, less radical
decline continues to the 150 to 175 mm class. Studies of released and recap-
tured females reveal that the period of maximum growth may accelerate re-
moval of individuals from the intermediate size classes into larger classes. Re-
lative scarcity of members of the 150 to 175 mm class was observed through-
out the study.
The second peak in abundance at the interval 225 to 250 mm is associated
with attainment of sexual maturity in females (at around 220 mm) and a sharp
decline in growth rate. Growth has virtually ceased in most females over 250
mm; thus members of this size class probably accumulate as new individuals
mature and growth ceases. The size at which growth essentially ceases, how-
ever, varies, as indicated in Figure 24, where there are only slight differences
in frequency of size classes between 230 and 265 mm.
In males (Fig. 25), a more "normal" distribution centering around the size
class 90 to 95 mm is evident. Growth declines, though less sharply than in fe-
males, after attainment of sexual maturity (80 mm CL). There is less variation
in the size at which growth in males essentially ceases. More than half (58%)
of mature males were between 85 and 100 mm in length.



Il 20-
(r 15-



30-50 50-75 75-100 100-112525-ISO 150-175 175-200 200-25 225-250 250-5S 275-300
Figure 23. Relative abundance of size classes of juvenile and adult female Graptemys pulchra
from the Conecuh River, Escambia County, Alabama.

Vol. 21, No. 2





Z '12-
Z) 10-

: 8-



225- 230- 235- 240- 245- 250- 255- 260- 265- 270- 275-
230 235 240 245 250 255 260 265 270 275 280

Figure 24. Relative abundance of size classes of adult female Graptemys pulchra from the
Conecuh River, Escambia County, Alabama.



I- I -- I -- I
60- 70- 75- 8- 85- 90- 95- 100- 105- 110- 115-
70 75 80 85 90 95 100 105 110 115 120

Figure 25. Relative abundance of size classes of adult male Graptemys pulchra from the
Conecuh River, Escambia County, Alabama.



Field observations of nests indicate that nest destruction probably exceeds
90 percent in most seasons, i.e very few eggs develop and contribute hatch-
lings to the population. These observations are consistent with those of other
workers (Allen 1938, Cagle 1950, Gibbons 1968, Moll and Legler 1971), who
found egg mortality to be as high as 99.8 percent. Numbers of hatchlings
added to the study area population per year appeared to vary somewhat dur-
ing the study period. For example, during the late fall of 1969 and spring of
1970 hatchlings were relatively abundant but were scarce during the follow-
ing three seasons.

Few instances of natural post-natal mortality were observed; one juvenile
female, several young adults, and several old adults were found dead of un-
known causes during periods of rapidly dropping water level. These obser-
vations occurred during early spring and summer. On a nesting beach a
freshly killed young adult female was found, surrounded by raccoon tracks
(Fig. 26).

Figure 26. Freshly killed nesting female Graptemys pulchra (AUM 21973) at the Conecuh
River, Escambia County, Alabama (sandbar of Figures 2, 20, and 21). Note egg shells in fore-
ground. Predator was probably a raccoon.

Vol. 21, No. 2


Under laboratory conditions hatchlings and very small individuals were
especially delicate. Thus, it is assumed that very small individuals would be
most susceptible to natural stresses. The data in Figure 23 support the con-
clusion that significant mortality after hatching occurs in size groups under
175 mm in carapace length. Ernst (1971) likewise found a significantly higher
mortality among juvenile C. picta than among adults, but Gibbons (1968)
found a lower mortality in juveniles.
During the first few years of growth the shell is comparatively soft and
offers little resistance to injury. At this time very young individuals probably
direct nearly all food resources toward growth rather than energy storage
during most of the year. Thus, with even a brief decline in food quantity or
quality, a lack of metabolic reserves may result in decreased vigor and in-
creased susceptibility to disease and injury. Among adults such stresses are
probably detrimental only if prolonged or extreme. The observed adult mor-
tality is attributable to shooting by man, to unknown diseases, or to some un-
known predator. Occasionally individuals collected during periods of flood-
ing had freshly eroded, bleeding, and evidently infected areas on the plastron.
Definition of home range within a habitat that undergoes drastic changes
annually or seasonally is necessarily tenuous. Populations of G. pulchra were
found to congregate in particularly favorable areas. Although apparently
subtle, changes associated with seasonal fluctuations in water level, especially
sand and silt distribution, often resulted in major redistributions of individ-
uals. Sexton (1959b) found that Chrysemys picta emigration coincided with
high water levels.
In areas less subject to seasonal changes distribution was consistent and
predictable to the extent that certain logs and trees would be expected to
serve as basking sites for a specific number of individuals of each species.
Chaney and Smith (1950) and Cagle (1952) also noted such behavior in G.
pulchra with respect to home range.
Variation in home range was most pronounced from year to year. At the
close of a period of intense marking efforts in the fall of 1969 in a moderately
stable area near East Brewton, it became difficult to find unmarked individ-
uals, and the next year only 10 of the original 62 marked individuals were re-
covered. In the following two years, I recovered 12 and 4 members, respec-
tively, of the original group. Thus, even though the area apparently remained
the most favorable one within the immediate vicinity (a km in either direction)
and the population density remained stable, significant movement had oc-
curred. The distance between favorable areas was generally several hundred
meters, depending on river channel characteristics, and most individuals
probably did not often move between these areas during a single season. Al-
though a quantitative estimate of home range size was not made, it is prob-


able that the area involved was similar to Moll and Legler's (1971) estimate
of 278 m of river for P. scripta.
Homing ability has been demonstrated in many emydines (Cagle 1944a,
Legler 1960, Moll and Legler 1971). Distances in excess of 2000 m have been
traversed, upstream and downstream, in returning to a home range. Such
movements may also be quite rapid. One sonically tracked female P. scripta
moved 1000 m in 90 minutes after being displaced from its point of capture
(Moll and Legler 1971).
To determine homing tendency in G. pulchra, 47 marked individuals (13
males and 34 females) were released 24 channel km upstream (66, 159) or
downstream (7S, 199) from capture sites. Release and recapture data on
eight displaced and recovered individuals are shown in Table 4. All recovered
individuals were females, implying either less adherence to home range or
less homing ability in males. On the basis of similar data, Cagle (1944a)
reached the conclusion that males of P. scripta move randomly when dis-
placed. However, other available data for G. pulchra show that males may
be responsive to home range, for of 53 non-displaced males 42 percent were
recaptured near the point of release (Table 5). Since more non-displaced males
than females were recovered, movements of males may be regulated by other
factors, such as food availability.
Half the recovered females returned to the point of capture, while half
remained at the point of release (Table 4). Because of the great distances in-
volved (approximately 24 km) and the small size of the collecting areas (1 to
4 km), it is not likely that either homing ability was absent or that random
movement occurred from the point of release. The same proportion (24%)
of females was recovered both in displaced and in non-displaced groups, indi-
cating that individuals either returned to the original point of capture (home
range) or remained in the areas of release, but did not wander randomly
(Table 5).
As shown above (Moll and Legler 1971), such returns may be accom-
plished in comparatively short periods of time. It is unlikely that any re-
covery failure resulted from lack of sufficient travel time.
Of the four displaced individuals that returned, two returned to an up-
stream home range and two returned downstream (Table 4), indicating that
homing ability may be unaffected by direction of stream flow. Downstream
return in this case implies that olfaction was not involved. Channel charac-
teristics, with associated factors such as current velocity, stream width, and
bottom structure, are perhaps the most likely qualities used as cues for navi-
gation in this case.
No signs of territoriality were detected in G. pulchra during this study.
Cagle (1944a) stated that territoriality was evidently non-existent in the
genera Pseudemys, Chrysemys, Chelydra, and Sternotherus.

Vol. 21, No. 2


No. C.L. Date, points of Date, point Interval Return
(mm) Capture-release of recapture (months)

Aug., 1969; 29-4
May, 1971; 4-29
May, 1971; 4-29
Aug., 1969; EB-4
June, 1972; EB-4
May, 1971; 4-29
May, 1971; 29-4
May, 1971; 29-4
May, 1971; 4-29

Aug., 1970; 29
June, 1971; 29
Mar., 1972; 29
June, 1972; EB
Sept., 1972; 4
June, 1972; 4
Sept., 1972; 4
Sept., 1972; 29
Sept., 1972; 29




Up >z

in months of


*Abbreviations: No. individual marking number; C.L. -carapace length in millimeters; 29-U. S. Highway 29; 4-Escambia County Highway 4; EB-East Brewton. Interval is
growth between release and recapture. Return is direction of movement from point of release, if movement occurred. Distance between points is approximately 15 river channel miles.





Number Number Percent
Released Recovered Recovery

Males 13 0 0
Females 34 8 24
Total 47 8 17

Males 53 22 42
Females 111 27 24
Total 164 49 30


Food of Graptemys pulchra in the study area falls into two general cate-
gories: arthropods (especially insects), which were important to males and to
juvenile females during the first few years of growth; and molluscs (bivalves
and gastropods), essentially the only food source for older juveniles and adult
females. Cagle (1952) found a similar situation in Pearl River specimens. Some
other Graptemys may be omnivorous (Cahn 1937), and others are primarily
molluscivorous as adults (G. barbouri, Carr 1952).
As indicated in Figure 27, individuals less than 100 mm in carapace length
are almost entirely insectivorous. In 36 fecal samples having identifiable
arthropod remains, including samples from adult males, the following groups
and frequencies were found: Trichoptera (as schlerotized larval fragments
and cases), 27; Coleoptera (mostly terrestrial adults), 18; Odonata (nymphs
and adults), 11; Hymenoptera (adults), 5; and millipedes (Diplopoda), 3.
Webb (1961) found case-building Trichoptera, as well as Odonata, Coleop-
tera, and crayfish to be important food items of G. pseudogeographica.
A dietary shift to molluscs occurs in females at 80 to 100 mm CL, with in-
sects occasionally being represented in larger juveniles (Fig. 27). The most
important molluscan food item by far is the imported oriental mussel, Corbi-
cula maniliensis (Fig. 28). This mussel probably represents the predominant
macrozoic biomass in the study area. It was so abundant in some bottom situ-
ations that a sample of the top 3 cm of substrate often yielded equal volumes
of Corbicula and sand. During some periods of rapidly dropping water level,
shells were deposited on sandbars in concentrations of several hundred per
square meter. Corbicula represented at least 95 percent of all food consumed
by adult females. Some correlation was found between carapace length and

Vol. 21, No. 2


100- ** g o *



D 40
> 20-
** *
o- o, *4 *

40 60 80 100 120 140 160 180 200 220

Figure 27. Ontogenetic dietary shift in female Graptemys pulchra from the Conecuh River,
Escambia County, Alabama. Importance of molluscs is expressed as percentages of fecal re-
mains. Arthropods constitute the alternate food item.

size of Corbicula eaten (Fig. 29). Individuals under 150 mm CL fed mostly
on mussels from 2 to 12 mm in length, while individuals over 150 mm CL fed
on all sizes of mussels, particularly those from 5 to 20 mm in length. Adult
females (over 220 mm CL) fed mostly on mussels from 15 to 25 mm long.
Figure 29 does not show the relative importance of various mussel size classes,
The remaining 5 percent of the adult female diet in the study area in-
cluded native mussels (generally under 50 mm, the largest Corbicula were
30 mm long), common aquatic snails, and crayfish (one sample). Fecal samples
of adult females from the Mobile River drainage, where Corbicula was not
found, contained mostly native mussels from 30 to 50 mm in length. One fecal
sample from a Mobile Bay drainage specimen contained fish vertebrae, im-
plying that carrion may be an occasional food source. Captive hatchlings
seem to prefer fish to insects and crayfish.
Adult males, although primarily insectivorous, fed occasionally on small
mussels and snails. Small aquatic snails represented about 15 percent of the
volume of fecal material among 11 adult males. This figure may overestimate
the importance of molluscs as a food source, however, since proportionately
much less digestible material may be present in snails than in insects. Small
numbers of minute Corbicula shells were frequently found in male fecal sam-
ples, but did not constitute an important item.
Some individuals in their first few seasons of growth contained highly

6 6 4

4 6 *o *.

utint~ (I .II 1 1 1 1111111T T 1 9 1T T11 1 11 1 11


(?^ ~

Figure 28. Corbicula maniliensis from the Conecuh River, Escambia County, Alabama.
Left, representative shells from fecal samples of adult female Graptemys pulchra. Right, shells
stranded by receding water near East Brewton, Alabama.




3 24-


F -
lJ 16-

< 12-

0 8-



100 120 140 160 180 200 220 240 260 280

Figure 29. Size of Corbicula ingested as a function of carapace length in female Graptemys
pulchra from the Conecuh River, Escambia County, Alabama.

eroded fragments of large Corbicula shells, much larger than could possibly
have been crushed by turtles of such small size. This, combined with the facts
that only incomplete shells were found, and that fragments were not greatly
eroded by a single passage through the digestive tract of large individuals,
led to the conclusion that fragments expelled by large individuals were in-
gested by small individuals. The reason for this cannot be determined, but
it may be related to the obtainment of calcium salts for shell development
or other needs. Moll and Legler (1971), speculating on the occurrence of snails
in the diet of Pseudemys scripta, believed that "females may feed heavily on
snails prior to the nesting season to build up stores of calcium for egg shell
Captive adult females kept in artificial pools (about 4 m in diameter and
50 cm deep) fed on crayfish almost exclusively, even though mussels were
made readily available. Although crayfish were abundant in adjacent swamps
and lowlands, the scarcity of crayfish in the Conecuh River (only one seen
in four years) precluded their significance as a food item. It seems unlikely
that G. pulchra could regularly catch healthy crayfish, even if they were
It is likely that mussels were eaten by grasping them with the jaws, pulling
them out of the sand, and crushing them with the broad lateral alveolar sur-
faces of the jaws. Large females often showed pronounced erosion on the

Vol. 21, No. 2


lateral alveolar surfaces and none on the mandibular apex, resulting in a
hooked condition of the lower jaw. This prevented the mouth from being
sealed when closed. Small mussels and snails were occasionally swallowed
entire, as evidenced by the presence of unbroken shells in the feces. The front
feet were probably not used as extensively in feeding on molluscs as on arthro-
pods, since mussels were not torn apart before being eaten.
Presumably because of the low food value to weight ratio of molluscs,
fairly large quantities of mussels were consumed. The small intestine of an
adult female is about 10 mm in diameter when empty, but many intestines
were found distended to 30 mm in diameter for as much as 15 cm along their
length, totaling 106 cc in volume. Usually within a day or two after capture
all of the intestinal contents were expelled, implying that such a quantity
represents no more than a single daily feeding.
Small individuals frequently were seen browsing in shallow water near
sandbars or heavily sloping banks, or more commonly among drifts of floating
debris that harbored large numbers of insects. Feeding on caddisfly larvae,
the most important food source, was not seen. Case-building caddisflies are
probably found in areas not visible from the surface. Also, feeding is probably
inhibited by the presence of a diver. Young turtles and adult males seemed
equally adept at feeding on floating prey or on submerged items. As in other
emydines, the claws of the front feet are commonly used as an aid in tearing
food into bite-sized morsels.
Very few data are available to elucidate the diel aspect of the feeding
cycle. Captive specimens fed at various times. Large individuals observed
while diving during the day were generally inactive and among submerged
cover. Surface feeding by individuals of various sizes was observed only dur-
ing early morning hours. The remainder of the day, especially during the
spring and most of the summer, was spent basking and among cover. Boyer
(1965) remarked that the stomachs of basking Graptemys often were packed
with food items. Basking has been shown to be linked with feeding in other
aquatic emydines (Moll and Legler 1971). Regal (1966) showed that in cer-
tain Squamata, digestion may depend on thermoregulation to the extent that
prolonged maintenance of suboptimal temperatures following a meal may be
In adult females heavy feeding began in May and essentially ceased in
October. Small individuals and males apparently fed as late as November.
Feeding coincided rather closely with the annual activity cycle (see pp. 99-
The major determinant of seasonal activity is water temperature. In the
study population feeding essentially ceased and general activity sharply de-
clined as water temperatures fell below 190C (660F). This was in contrast


to temperature relationships of some other aquatic emydines. Ernst (1971)
reported Chrysemys picta "active" at water temperatures as low as 100C;
Cagle (1950) reported a similar minimum temperature for activity in Pseu-
demys scripta. Pseudemys concinna in the Conecuh River study area was
never found inactive, even though the water temperature dropped to 11C.
Carr (1952) observed similar differences between G. barbouri and P. flori-
dana with respect to temperature relationships.
Water temperatures below 190C, coupled with changes in feeding and
activity in Graptemys pulchra, occurred regularly in early to mid-April and
in late October to early November. During the summer months when water
temperatures reached 300C (860F), little correlation was observed between
water temperature and either basking or underwater activity. Boyer (1965)
found this to be true for aquatic turtles generally. However, during times of
extremely hot weather, high water temperatures, and low water levels
(August and September) in the study area, there was a marked decrease in
Some basking activity was observed during all months, even during warm
periods in winter months when the water temperature was as low as 11C.
When both water and air temperatures were low (November to February),
long periods of inactivity resulted. Prolonged inactivity was evidenced by an
accumulation of silt on torpid individuals found resting on the bottom in
deep, silted pools, usually wedged among limestone boulders or sunken trees.
Such individuals were reluctant to move when disturbed and when they did
move, they were extremely lethargic. Carr (1952) noted similar behavior in
G. barbouri. The head and appendages were normally somewhat withdrawn
into the shell, a pose never observed during months of activity.
A sharp peak in basking activity regularly occurred in March and April
and was associated with high water levels caused by spring rains. Basking re-
mained extensive from May through July but normally declined from July
to October.
Other species of turtles in the same habitats with G. pulchra showed dif-
ferent activity patterns. Macroclemys temmincki, observed on several oc-
casions during the winter, was always found deeply imbedded headfirst in
the bottom mud, with the tail either exposed or close to the substrate surface.
Pseudemys concinna showed no reduction in underwater activity during
winter months. Swimming speed remained high and response to approach
by a diver was rapid, even at minimal water temperatures. It was not deter-
mined whether feeding continued through the winter in P. concinna, but it
is unlikely that the sharp growth rings observed in this species in the study
area could have resulted if feeding had been continuous.

Vol. 21, No. 2


Basking was the most conspicuous daily surface activity, and it occurred
at all times of day. The basking habits and requirements of G. pulchra were
essentially the same as for turtles studied by Boyer (1965).
The basking drive in G. pulchra is obviously intense. Individuals kept in-
doors for several weeks with no opportunity to bask were seen mounting bask-
ing sites immediately after being released. On one occasion, a large female
climbed onto a sandbar, the closest exposed surface, within minutes after
being released. As a rule, individuals of this species strongly avoid such ex-
posure, except while nesting. Moll and Legler (1971) found an increased
tendency to bask in P. scripta when sites were unavailable for long periods
of time.
Although the functions of basking are probably manifold, Auth (1975)
concluded that thermoregulation is the primary function in Chrysemys
scripta. Both he and Boyer (1965) state that basking is dependent upon the
interaction of several factors, of which ambient water and insolation tempera-
tures are most important.
In G. pulchra two functions of basking appear paramount: (1) to provide
a mechanism for increasing body temperature, and (2) for maintenance of a
healthy integument through inhibition of fungal and algal growth, ectopara-
sites, and bacterial infections. Captive individuals that are unable to bask,
especially if small, are highly susceptible to infestation by an unidentified
fungus. Growth of the fungus usually begins between the toes or in the in-
guinal or axillary pits, eventually affecting the entire skin. When the infesta-
tion reaches the latter stage, the turtle is not likely to survive, even with treat-
ment. Small individuals and males are much more susceptible than adult fe-
The only ectoparasite observed during the study was the aquatic leech,
Placobdella sp., which apparently could survive nearly as much exposure as
its host. During basking, a leech normally contracts its body into a spherical
shape, thereby reducing the surface area and thus its susceptibility to desi-
Environmental factors associated with increased basking in the field in-
cluded high water levels, warm air temperatures, and bright skies. Basking
did not occur in G. pulchra or in any other species on cloudy days when water
temperature exceeded air temperature. This implies that the function of bask-
ing is primarily thermoregulatory, and is not principally associated with dry-
ing of the integument. The same conclusion was reached by Boyer (1965) and
Auth (1975).
Basking behavior supports the hypothesis of thermoregulatory function.


The turtles often spent several hours out of the water, during which they pre-
sumably maintained a high body temperature and a correspondingly high
metabolic rate. Partially shaded basking sites often seemed to be favored, es-
pecially during late summer. Such sites perhaps allowed prolonged high body
temperatures without exceeding maximum tolerances. Individuals that have
been basking for some time (as evidenced by a completely dry shell) often
exhibited a "panting" behavior. Whether such behavior was in response to
excessively high temperature is uncertain, but it characterized individuals
that had been basking for long periods in mid-day sunlight. Boyer (1965) and
Moll and Legler (1971) showed that gaping was associated with temperatures
approaching the "critical maximum." Such individuals were unusually sensi-
tive to disturbances. They were approached with great difficulty, often drop-
ping off the basking site over a hundred meters in advance of a swimmer who
had only the top half of the head exposed above the water. Probably because
of the effects of heating, surface collecting was generally much more produc-
tive during morning hours. On the other hand, members of the genus Grapt-
emys are well known for their extreme wariness while basking, which seem-
ingly is independent of high body temperature. Newman (1906) noted that
startled birds flying from the shore or frogs jumping into the water caused
abrupt reentry by Graptemys.
Basking in covered and shaded situations was observed frequently during
periods of high water, when such sites were the only ones available. Most indi-
viduals, especially very large females and hatchlings, seemed to prefer cov-
ered basking sites. Presumably hatchlings tend to use such sites because of
the protection they offer. Large females may have been selectively favored
by offering less conspicuous targets for "plinkers." Carr (1952) suggested that
the extreme wariness of Pseudemys rubriventris might be due to its long-time
persecution by man, "who has been weeding out the unwary individuals for
a century or more." An additional, and perhaps overriding, advantage to such
sites may be that they provide for a less radical body temperature increase
that does not exceed requirements for digestion and metabolism.
Adults were particularly conservative in their selection of basking sites.
Freshly fallen trees seemingly offered ideal sites but were generally not used
by adults during the same year, unless other basking sites were extremely
scarce. Even when other sites were scarce, however, turtles would generally
prefer to travel several hundred meters to apparently more familiar sites.
Moll and Legler (1971) found that P. scripta would not bask on artificially
anchored sites, even though the sites were constructed of logs that were
identical to those at their familiar sites.
In the Conecuh River, basking sites were usually parts of trees that had
been undercut and had fallen into the stream. The sites most frequently used
had several qualities in common. Most importantly, a site did not have an ex-
posed continuity with the shore, a feature also noted by Boyer (1965) and by

Vol. 21, No. 2


Moll and Legler (1971). Trunks and branches of overhanging willows, which
were favorite basking sites during high water, were strictly avoided when
the water level dropped sufficiently to cause the exposed trunk to be con-
tinuous with the shore. As little as 30 cm of open water sufficed to make such
a site acceptable. As noted by Cagle (1952), sites associated with deep holes
and swift currents were preferred, as were trees that had lost most of the
smaller branches. Other qualities being equal, sites providing the greatest
field of vision seemed to be preferred. Given time, basking individuals habitu-
ally moved to the highest possible point on the site. Boyer (1965), who ob-
served the same behavior in Louisiana Graptemys, considered its purpose to
be the gaining of an improved vantage point.
While basking, the fore feet are normally used to maintain position, while
the hind feet are often extended with the toes spread, allowing exposure of
maximum surface area. If a point of balance is achieved on the basking site,
the fore legs are also extended. The head and neck are invariably extended,
perhaps as much for surveillance as exposure. Indentical behavior has been
observed in P. scripta (Moll and Legler 1971) and in emydines generally
(Boyer 1965).
Basking adults were occasionally observed to wave the forelegs repeatedly
against the sides of the head, as if brushing away some source of irritation.
This behavior may have been caused by gnats or mosquitos, which were
attracted to the eyes.
Various species of turtles dropping from basking sites commonly alerted
basking individuals of G. pulchra. Trionyx spp. were especially sensitive to
disturbances, and its hasty reentry often alerted other turtles. Pseudemys con-
cinna also served a "sentry" function among basking groups. The resounding
splash of a large female G. pulchra or P. concinna dropping several meters
from an overhanging tree, under conditions of concentrated basking, often
initiated a chain of plunges extending for several hundred meters along the
river. As a result, it often happened that fewer individuals were collected
when basking was extensive than otherwise. It was noted that splashes caused
by fishes, kingfishers, or even occasionally swim fins did not normally alert
basking turtles.
Very little information on nocturnal activity in G. pulchra was obtained. A
few individuals were found at night lingering close to the surface among ex-
posed branches and roots, as was also reported by Chaney and Smith (1950)
in the Pearl River. No individuals were found feeding or located in hiding
places favored during the day. Thus, the nature and extent of nocturnal ac-
tivity in the field remains essentially unknown.
Specimens kept in outdoor pools were consistently observed at night ac-
tively searching the bottom. Feeding was observed only at night among
adults, but at all times among small individuals. In the field adults were us-
ually found hiding during the day, but small individuals were found both in


hidden and in exposed areas, presumably feeding. One may surmise from this
that adults feed principally at night and bask or remain hidden during the
day, whereas immature individuals follow a much more flexible routine.

Nest predation is by far the most significant inhibiting factor on popu-
lation growth in Graptemys pulchra. As indicated in the discussion of repro-
duction, at least 95 percent of all nests found at the study area were destroyed
by predators. Similar rates of predation in other species have also been cited
by Allen (1938), Cagle (1950), and Moll and Legler (1971).
Cagle (1950) found the most important predator of Pseudemys scripta
nests in the populations he studied to be skunks, raccoons, and snakes. The
major diurnal predator of G. pulchra nests was the fish crow, which evidently
patrols the beaches regularly looking for nesting females. Tracks on nesting
beaches indicated that crows may follow a nesting female to the nesting site.
Whether crows waited for the completion of the nest before eating the eggs
is unknown, but nests destroyed by crows characteristically showed signs of
excavation. Eggs were normally carried away from the nest before being
eaten, as evidenced by the absence of shells at the nest site and the scattered
occurrence of shell fragments (Fig. 30).
The major nocturnal predator on nests was the raccoon. Some nests may
have been destroyed while under construction, but raccoons easily found
nests several days after laying, unless signs of the nest had been removed by
rain. Moll and Legler (1971) found that most nests were destroyed within 12
hours after laying and were located by the odor of turtle urine. Raccoons exca-
vated the nests, as did crows, but unlike crows, they ate the eggs at the site,
since the shells of most or all the eggs were found near the nest (Fig. 31).
In small streams (Opintlocco Creek, Cubahatachee Creek) of the Mobile
Bay drainage in Macon County, Alabama, predation seemed to be less in-
tense. Approximately 50-75 percent egg mortality was apparent in these
populations. The much smaller populations of G. pulchra resulted in a rela-
tive scarcity of nests in these areas. Since considerable energy would be re-
quired to locate nests, predators may have directed efforts toward more lucra-
tive sources of food.
Early in the study I had anticipated that the opossum would be an impor-
tant predator, but such was not the case. Even though opossums were com-
mon in the area, no tracks were seen on the nesting beaches. Another possible
predator of nests was skunks. Presumably skunks would leave signs similar
to those of raccoons, and some instances of predation may actually have been
due to skunks. Other potential predators of infrequent occurrence on the

Vol. 21, No. 2


' ~-'rv
r +

Figure 30. Nest of Graptemys pulchra destroyed by the fish crow, Conecuh River, Escambia County, Alabama. Note crow tracks at lower
left, turtle tracks at upper left, and egg shell at nest entrance.

: 6 ;.'

4. 4k

:u .. -, ,
*. ~~ S i
P ':. ; ,- ^ ^ J' ; }
'<~~~~~ ~~~ 'v r i*/.v -* t .^ "

*;eq -

W 4rr~

ti !dI~O



I~ It
., .. ". ', : t

," 0

Figure 31. Nest of Graptemys pulchra destroyed by the raccoon, Conecuh River, Escambia County, Alabama. Note crushed egg shells P
scattered around the nesting site and the wide excavation of the nest.



nesting beaches were bobcats and otters, but no instance of nest predation was
attributable to them.
Nests located in otherwise suboptimall" sites among vegetation or on
shaded banks seemed not to be destroyed as frequently as those in exposed
situations. An increased effort by the nesting female to conceal the nest may
have resulted from heavy predation of both nests and nesting females in the
study area.
No instance of hatchling predation was seen. It is likely that large preda-
tors, such as gars, herons, and alligator snapping turtles, feed at least occasion-
ally on hatchlings, but the extent of such predation remains unknown. Many
larger individuals were found with posterior portions of a rear leg, tail, or
carapace missing. Such wounds may have been made by alligator snapping
turtles, but fecal samples of several snappers failed to show turtle remains.
James L. Dobie (pers. comm.) found that the stomach samples of alligator
snappers often contained the remains of other turtles.
One instance of predation on adults was seen. A nesting female was found,
freshly killed, with the rear legs mangled and small holes torn in the inguinal
pit (Fig. 26). The injuries corresponded closely with those in an incident de-
scribed by Cagle (1950), in which crows had turned a female turtle over and
pecked holes in the inguinal pits. In the present instance there was no nest
cavity, but fresh egg shells were scattered around the site. Since the torn holes
were probably not large enough to allow extraction of the eggs, the female
probably extruded the eggs under stress. The only tracks in the area were
those of a raccoon.
The only significant predator of adults is man. Conversations with local
fishermen revealed that turtles were thought of as vermin, or at least as com-
petitors for the fish. Some residents, while drifting downstream or wandering
along the banks, used turtles for rifle targets. Several adult females had
wounds which may have been made by bullets. In one example, a projectile
had penetrated the upper neck region and the supraoccipital bone of the
skull. Carapace wounds were often recognized as having resulted from shoot-
Basking turtles were not normally alarmed by boats moving upstream
under power, however noisily, and were often literally washed off the bask-
ing sites by the wake. On the other hand, boats drifting downstream generally
alarmed nearby basking turtles. Thus, a boat drifting downstream could rarely
come within 30 m of basking turtles, while a boat driven rapidly upstream
could often approach to within a few meters. Possibly there was, on the part of
the turtles, an association of drifting boats with "plinkers." From such obser-
vations it seems that the state of wariness in individuals of G. pulchra is not
based so much on fear of threatening objects as on familiarity with harmless
objects or situations. Similarly, during periods of high water levels and re-


sultant extensive drifting debris, basking turtles were much less easily alarmed
by drifting swimmers or debris than during periods of low water and slight

Although a complete survey of parasites was not made, no instances of
deleterious degrees of parasitism were found during the study. A single ecto-
parasite, Placobdella sp. (a leech), was seasonally abundant in the study area.
It was commonly found on turtles during the spring, at which time the leeches
were often carrying many young.
The most common intestinal parasite was an acanthocephalan belonging
to the genus Neoechinorhynchus. It was never found in great numbers and
probably infected less than 25 percent of the adult population. A fluke, Telor-
chis sp., was also found in the small intestine of one adult female. Ernst and
Barbour (1972) listed a sporozoan, Myxidium chelonarum, in the bile duct and
gall bladder of G. pulchra.

Graptemys pulchra was the most abundant turtle found in the study area.
Other species, in order of decreasing apparent abundance, include Trionyx
spinifer, Pseudemys concinna, T. muticus, Sternotherus minor, Macroclemys
temmincki, and P. scripta. Very little effective competition among these spe-
cies was evident; probably the only situations in which this might possibly
occur involve young Pseudemys sp. and young and male C. pulchra, all of
which are insectivorous. Since food presumably was not a limiting factor,
probably little or no significant competition occurred. Competition for basking
sites may have been significant in some areas, but it was probably not impor-
tant at the population level.
Predator-prey interactions may be important between M. temmincki and
the young, and some adults, of other species. Specimens of Trionyx and Pseu-
demys, as well as of G. pulchra, were often found with a portion of a leg, tail,
or carapace missing. Such wounds were often smooth-edged and wedge-
shaped and could have been made by the shearing beak of M. temmincki.
James L. Dobie (pers. comm.) found other turtles to be an important food item
for Louisiana M. Temmincki; however, as previously indicated, the feces of
several isolated alligator snapper specimens captured at the study area con-
tained no turtle remains.
The most significant interaction observed was associated with basking.
Even though a slight tendency toward species uniformity in basking groups
was observed, interspecific "cooperation" was evidenced when alarmed indi-
viduals fell off basking sites, which in turn would cause similar reactions
among other members of the aggregation, regardless of species. The turtles

Vol. 21, No. 2


most sensitive to noise and disturbance were Trionyx sp., and these acted as
"sentinels" for the other less sensitive forms. Congregations of basking turtles,
regardless of species composition, were much more difficult to approach than
isolated individuals.


Species of the genus Graptemys occur in the extreme northern United
States. This, together with the fact that G. pulchra is found in the upper (i.e.
northern) portions of river drainages within its range, makes it unlikely that
latitude or altitude per se are important limitations to its distribution. Like-
wise, suitable annual temperature regimes occur well outside the present
range of the species. Consequently, it seems likely that its limitation to par-
ticular drainages results primarily from drainage isolation and absence of
overland migratory behavior. Ecological barriers are effective, however, as
evidenced by the absence of the species from certain major streams within its
range (e.g. Blackwater and Perdido rivers).
The physical and chemical characteristics of the medium- and large-sized
streams favored by G. pulchra presumably are major factors affecting the
species' distributions. Although the degree of adaptability to pond or lake
situations has not been determined, the species seems to survive at least mar-
ginally in such situations. There are no reports of its occurrence in artificial
impoundments of small streams or in natural (except oxbow) lakes, although
apparent stable populations have been observed in impoundments of large
streams, such as Gantt Reservoir (Conecuh River) in southern Alabama and
Weiss Reservoir (Coosa River) in northeastern Alabama.
The requirement of fine sand at nesting sites, if exhibited by populations
throughout the range, may be a limiting factor both within and outside the
species' range. Females within the study area were observed consistently
selecting nesting sites based on the degree of sand coarseness (see pp. 77-78).
Nest predation, which exceeded 95 percent during the study period, conceiv-
ably might reach 100 percent in some areas. Differential predation pressure
and vulnerability of the nests can alter the mortality rates.
Atmospheric basking probably is necessary for health, if not survival, in
G. pulchra (also see Auth 1975). Thus, the availability of basking sites may be
limiting in some situations, such as lakes, where these sites may be limited.
Within the study area, apparently two types of stresses on the general
population occur annually. These are the periods of winter inactivity (hiber-
nation?) and spring flooding. Shells of several dead individuals were found
after periods of flooding, although the precise time and cause of death were
uncertain. Moll and Legler (1971) found that tropical Pseudemys scripta ex-
amined during such periods showed reduced vigor and resistance to disease,
although the many specimens of G. pulchra collected during periods of high


water showed no reduction in fecal volume. Adult females with infected
plastra were occasionally found during periods of high water levels. Grapt-
emys pulchra may thus be somewhat more limited in abundance in areas sub-
ject to very frequent or extensive flooding, although this is thought to be less
important than certain other factors, particularly food availability.
It is unlikely that males of the species are limited by food availability, since
they are insectivorous. Feiales, on the other hand, are highly adapted to feed-
ing on molluscs, and thus may be restricted to areas where these animals are
found. It seems likely that the potential ecological range of the species is re-
structed by mollusc distribution, since within the range of G. pulchra the
effects of mollusc distribution are apparent. The greatest density of turtles
observed, which was in the study area, was associated with an extreme abun-
dance of molluscs, including several species of pelecypods and at least one
species of gastropod. Fecal samples of females from other areas (Mobile Bay
and Yellow River drainages) contained nowhere near the abundance of
mollusc remains as those of Conecuh River females. Few G. pulchra were
found in those streams supporting scant mollusc populations, and none at all
were found in streams in which molluscs were entirely absent. Conversely,
no stream within the range contains large mollusc populations and no G.
pulchra. Molluscs were consistently absent from brown-stained, probably
acidic, coastal plain streams, such as the Perdido and Blackwater rivers,
and the absence of G. pulchra from these systems likely is best explained on
this basis. It is tempting to speculate that a study of these and other streams
from which G. pulchra is absent would show that chemical factors preventing
calcium availability exclude both molluscs and G. pulchra.
Since no other "broad-headed" Graptemys occur with G. pulchra, com-
petitive exclusion from G. barbouri to the east, G. geographic to the north,
and G. kohni to the west may be limiting.

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