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Bull. Chicago Herp. Soc. 38(6):120-121, 2003
A Note on Sexual Dichromatism in Clemmys guttata from Erie County, Pennsylvania
Brian S. Gray
1217 Clifton Drive
Erie, PA 16505-5215
Sexual dimorphism in body size and coloration (dichromatism) is common in turtles (Zug et al., 2001). Sexual dichro-
71.6 mm. The turtle's chin coloration was reddish yellow,
characteristic of a female. The shape of the tail, condition of
matism has been reported from the following genera of North
the plastron (flat) and location of the cloacal opening (cloaca]
Caretta, Dermochelys, Apalone, Kinosternon, Clemmys, Emydoidea, Terrapene, and Trachemys (Ernst
opening not beyond margin of carapace) were also indicative of
et al., 1994). Sexual dichromatism in the spotted turtle
length, we identified it as a female based upon its chin color-
(Clemmys guttata) is exhibited by marked differences in both
ation and other characteristics (i.e.., flat plastron etc.). When
chin and eye coloration. Males have a tan chin and brown
recaptured on 15 April 2002, it had a 92.5 mm CL and 81.1
eyes; females a yellow chin and orange eyes (Ernst et al.,
mm PL. Comparing notes and photographs from the previous
American turtles:
1994). Ernst (2002 pers. com .) reported that
C. guttata from
a female. Although this turtle was less than 80 mm in plastral
capture in 1999, it was noted that the turtle's chin color was
Pennsylvania (Lancaster County), Maryland and northern
much darker, the plastron was now slightly concave, and the
Virginia are sexually dichromatic at hatching and that these
cloacal opening was beyond the rim of the carapace. The
differences in coloration do not change over time.
turtle, previously considered a female, was a male.
In this note we report changes in chin coloration from two
Turtle #0018 was captured on 17 May 1999, with CL of
C. guttata that were marked and subsequently recaptured at our
96.3 mm and PL of 81.6 mm. The chin was orange. The
study site in western Erie County, Pennsylvania.
plastron was flat, and the tail female-like, with the vent ap-
At time of capture the following data were collected:
straight line carapace and plastron measurements, sex, shell
anomalies and injuries, mass, estimated age, behavior, habitat,
proaching the rim of the carapace (Figure 1). This turtle was
also identified as a female.
This turtle was recaptured on 22 May 2000, while basking.
environmental conditions, cloacal and environmental tempera-
Its CL was 102.4 mm and its PL was 82.6 mm. No changes in
tures. After data collection, the turtles were marked with a
morphology or coloration were noted during this first recap-
numbered tag (National Band and Tag Co., Newport, Kentucky),
ture. On 15 April 2002, turtle 0018 was recaptured again with
photographed, and released at the point of capture. Upon each
a CL of 110.1 mm and a PL of 86.7 mm. The chin was now
capture / recapture, photographs were taken of the carapace and
dark, the plastron slightly concave, the tail was characteristic
plastron to document changes in pattern and new injuries.
of a male with the cloacal opening beyond the margin of the
Turtles were considered mature if their plastral length was
carapace (Figure 2). This turtle was a male.
greater than 80 mm (Ernst, 1970). Turtles were sexed using
the dichromatic characters (Ernst et al., 1994), and the presence of the following characters: males, concave plastron, vent
located beyond the rim of the carapace; females, a flat to
slightly convex plastron, cloacal opening located anterior to the
margin of the carapace (Ernst and Barbour, 1972).
Turtle #0012 was hand captured on 26 April 1999. It had a
120
Paul Curtis
Erie Zoo
423 West 38th Street
Erie, PA 16508
This is the first report of female chin coloration occurring in
subadult male C.
guttata. It is also the first time that changes
in the coloration of the chin have been documented for this
species. Our observations are significant because it has been
implied that chin and eye coloration can be used to sex hatchling spotted turtles (Ernst et al., 1994). At this time the
cause(s) of these changes (in coloration) are unknown. We
carapace length (CL) of 80.7 mm and a plastron length (PL) of
have ruled out organic staining as a possibility, as coloration on
Figure 1. Turtle #0018, ventral view, on 17 May 1999. Note the
light coloration of chin and gular region.
Figure 2. Turtle #0018, ventral view, on 15 April 2002. Note the
dark chin and gular region.
characters to sex juvenile C. guttata.
the tail, limbs, and plastron was not affected. Pollution also
seems unlikely, but is worthy of further consideration. Con-
Litzgus and Brooks (1999) have demonstrated that spotted
taminants that cause endocrine disruption, such as polychlorinated biphenyls (PCBs). may elicit sex reversal in reptiles with
temperature dependent sex determination (Guillette, 2001).
turtles in a northern population in Ontario, Canada, reached
sexual maturity at a larger size relative to more southern conspecifics. One of our turtles (#0018) did not acquire the dimor-
Another possibility is that in some populations, male spotted
phic characters typical of a mature male spotted turtle (e.g.,
turtles normally undergo ontogenetic changes in chin color-
concavity of the plastron, cloacal opening beyond carapacial
ation. In our turtles, changes in chin coloration seemingly
coincided with changes in the plastron, tail, and location of the
cloacal opening relative to the carapacial margin indicative of
sexual maturity. It is interesting that changes in chin coloration
have not been observed in other, more southern populations.
rim, etc.), until after a carapace length of 102.4 mm and a
plastron length of 82.6 mm were reached.
Acknowledgments
More work needs to be done to determine the cause(s) of
We wish to offer our thanks to Scott Bloomstine and Mark
changes in coloration, and to determine the distribution and
Lethaby for their assistance in the field; to Michael Klemens,
prevalence of such changes in other populations. We suggest
Art Hulse, and James Harding for providing comments and
that workers use caution when using sexually dichromatic
suggestions that improved the manuscript.
Literature Cited
Ernst, C. H. 1970. Reproduction in Clemmys guttata. Herpetologica 26:228-232.
Ernst, C. H., and R. W. Barbour. 1972. Turtles of the United States. Lexington: Univ. Press of Kentucky.
Ernst, C. H., J. E. Lovich and R. W. Barbour. 1994. Turtles of the United States and Canada. Washington, D.C.: Smithsonian
Institution Press, Washington, D. C.
Guillette, L. J., Jr. 2001. Contaminant-associated endocrine disruption in reptiles. Pp. 595-615.
In: D. W. Sparling, G. Linder, and
C. A. Bishop, edirors, Ecotoxicology of amphibians and reptiles. Pensacola, FL: SETAC Press.
Litzgus, J. D., and R. J. Brooks. 1999. Growth in a cold environment: Body size and sexual maturity in a northern population of
spotted turtles, Clemmys guttata. Can. J. Zool. 77:773-782.
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