SREL Reprint #3232

Overwintering of Gopher Tortoises (Gopherus polyphemus) Translocated to the Northern Limit of Their Geographic Range: Temperatures, Timing and Survival

Brett A. DeGregorio1,2, Kurt A. Buhlmann1, and Tracey D. Tuberville1

1Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29801 USA
2University of Illinois, Department of Natural Resources and Environmental Science,
1102 S Goodwin Avenue, Urbana, Illinois 61801 USA

Abstract: We examined overwintering behavior in gopher tortoises (Gopherus polyphemus) translocated to the northern periphery of their geographic range by using miniature temperature data loggers during 2 winters. All adult and juvenile tortoises monitored with temperature loggers survived overwintering; however, during the course of the study 2 translocated juvenile tortoises without temperature loggers died during winter months. Onset and termination of overwintering were not different between the 2 yrs and were not correlated with mean above-ground air temperature. Mean overwinter duration was 127 ± 9 d SD and 128 ± 13 d SD during 2002–2003 and 2004–2005, respectively. Tortoises experienced temperatures as low as 7°C and as high as 31°C while overwintering; however, most (12 of 15) tortoises experienced very little (< 1°C) mean daily temperature fluctuation despite air temperatures regularly dropping below 0°C and exceeding 20°C. The overall mean temperature of overwintering tortoises was 12.4° ± 0.8°C (2002–2003) and 12.6° ± 1.2°C (2004–2005). Large fluctuations in temperature occurred when tortoises actively basked, and half of the monitored tortoises did, particularly juveniles, which accounted for 42% of winter basking events. Our results suggest that, given timely access to suitable refugia at recipient sites, overwinter mortality of translocated adult individuals may be minimal.

Keywords: Reptilia; Testudines; Testudinidae; thermal ecology; conservation; translocation; gopher tortoise: Gopherus polyphemus; iButtons; dormancy; overwintering

SREL Reprint #3232

DeGregorio, B. A., K. A. Buhlmann, and T. D. Tuberville. 2012. Overwintering of Gopher Tortoises (Gopherus polyphemus) Translocated to the Northern Limit of Their Geographic Range: Temperatures, Timing and Survival. Chelonian Conservation and Biology 11(1): 84-90.

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