SREL Reprint #2253

Daily body temperature variation in free-ranging rubber boas

Michael E. Dorcas1,2 and Charles R. Peterson1

1Department of Biological Sciences, Idaho State University, Pocatello, ID 83209, USA
2Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802, USA

Abstract: A current generalization regarding body temperature (Tb) variation in free-ranging reptiles is that, when possible, they maintain relatively high Tb's to optimize important biological functions. However, because this generalization is based primarily on studies using opportunistic spot measurements of diurnal lizards, it is both phylogenetically and ecologically biased in addition to underrepresenting inactive animals. We addressed these problems by continually monitoring Tb variation in free-ranging rubber boas (Charina bottae), a nocturnal boid. We surgically implanted temperature sensitive radiotransmitters into 14 female snakes and monitored their Tb's at 5-min intervals for periods of up to a year (September 1990 to September 1992) using an automated monitoring system. Operative environmental temperatures (Te's) were concurrently measured using physical snake models. We describe four daily Tb patterns, including a previously undescribed pattern in which snakes were nocturnally active, frequently at unusually low temperatures (modal activity temperature = 14 C). Nocturnal activity occurred about once every eight days. As found in previous studies, pregnant snakes maintained higher and less variable Tb's than nonpregnant snakes, which is likely important for maintaining a high developmental rate. Our results also support findings from another study in which the thermal environment prevented snakes from maintaining high, stable Tb's much of the time. However, unlike previous studies, we found that when unconstrained by the thermal environment, snakes did not maintain high stable Tb's much of the time. These results raise questions regarding the predictability of reptilian thermoregulation using environmental temperatures.

Keywords: Charina bottae; Body temperature; Operative temperature; Body temperature pattern; Thermal utilization; Thermal constraint; Reproductive condition; Activity; Nocturnal activity; Physical environment; Radiotelemetry

SREL Reprint #2253

Dorcas, M.E. and C.R. Peterson. 1998. Daily body temperature variation in free-ranging rubber boas. Herpetologica 54:88-103.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).