SEASONAL BODY TEMPERATURE VARIATION IN THE EASTERN PAINTED TURTLE (CHRYSEMYS PICTA)
Kristine Grayson and Michael E. Dorcas
Davidson College
For ectotherms, body temperature plays an important role in many aspects of their thermal biology including their activity, metabolism, and growth (Bennett and Dawson, 1976; Cossins and Bowler, 1987; Grant, 1990; Huey, 1982). In studies of thermal biology, body temperature patterns of free-ranging animals are often determined based on a limited number of spot measurements of active animals, even though most ectotherms are inactive most of the time (Dorcas and Peterson, 1998). Understanding patterns of body temperature variation is the first critical step to developing a through understanding of ecothermic thermal biology.
Unfortunately, little is known about the seasonal temperature variation of most
ecotherms. Painted turtles (Chrysemys picta) have been used as model
organisms for many ecological and evolutionary studies on ectotherms, however
little is known about their thermal biology in the field (Packard and Packard,
2001). Most recent studies have focused on the physiological adaptations of
cold tolerance in laboratory studies, particularly in hatchlings (Costanzo et
al., 2000; Packard and Packard, 2001; Ultsch et al, 1999). Additionally, most
thermal research in the field has been conducted in the northern portions of
their range (Koper and Brooks, 2000; Litzgus et al., 1999; Peterson, 1987).
I hypothesize that a free ranging southern population will have higher, more
variable overwintering temperatures than northern populations and will not exhibit
freezing. I propose to test my research hypothesis using the newest advances
in micro-dataloggers to describe seasonal body temperature variation in free-ranging
painted turtles. We have conducted a turtle mark-recapture program since 1999
at a farm pond in Davidson, NC. Our annual recapture rate is greater than 90%,
thus allowing retrieval of individual turtles and their dataloggers with high
reliability.
The miniaturization of computer-controlled micro-dataloggers offers the opportunity
to examine, in detail, the seasonal body temperature variation in turtles. One
of the newest developments in temperature data collection are microdataloggers
called Ibutton Thermochrons (Dallas Semiconductor). Each Thermochron is protected
by a stainless steel casing, approximately the size of four stacked dimes (16mm
wide, 6 mm thick, 3.5g), and is controlled through a serial computer interface
that records 2048 time and date stamped temperature readings (Dallas Semiconductor,
2001).
The Thermochrons will be sealed and attached to turtles using small cable ties.
I will monitor body temperature variation over an entire year. For comparison
to body temperature, I will simultaneously monitor variation in environmental
temperatures using Onset dataloggers. This study will establish this innovative
technique as a standard method for measuring body temperature in small reptiles
and will provide data essential to understanding the physiology and ecology
of turtles. My research will provide the first critical step in developing a
complete understanding of painted turtle thermal biology and will help to elucidate
general patterns of variation in the thermal biology of animals across latitudinal
gradients.
References
Bennett, A. F. and W. R. Dawson. 1976. Metabolism. Pp.127-233. In C. Gans and W. R. Dawson (Eds.), Biology of the Reptilia, Vol. 5. Academic Press, New York, New York.
Cossins, A. R. and K. B. Bowler. 1987. Temperature Biology of Animals. Chapman and Hall, New York, New York.
Costanzo, J. P., J. D. Litzgus, J. B. Iverson, and R. E. Lee. 2000. Seasonal changes in physiology and development of cold hardiness in the hatchling painted turtle (Chrysemys picta). Journal of Experimental Biology 203: 3459-3470.
Dallas Semi-Conductor. I-Button Main Page. <http://www.ibutton.com/> Accessed December 2001.
Dorcas, M. E. and C. R. Peterson. 1998. Daily body temperature variation in free-ranging rubber boas. Herpetologica 54: 88-103.
Grant, B. W. 1990. Tradeoffs in activity time and physiological performance for thermoregulating desert lizards, Sceloporus merriami. Ecology 71: 2323-2333.
Huey, R. B. 1982. Temperature, physiology, and the ecology of reptiles. Pp. 25-67. In C. Gans and F. H. Pough (Eds.), Biology of the Reptilia, Vol. 12. Academic Press, New York, New York.
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Litzgus, J. D., J. P. Costanzo, R. J. Brooks, and R. E. Lee. 1999. Phenology and ecology of hibernation in spotted turtles (Clemmys guttata) near the northern limit of their range. Canadian Journal of Zoology 77: 1348-1357.
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Peterson, C.C. 1987. Thermal relations of hibernating painted turtles, Chrysemys picta. Journal of Herpetology 21: 16-20.
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