Meeting Abstract

P3.37  Thursday, Jan. 6  Long-term Field Study on Temperature Dependent Sex Determination in the Gopher Tortoise in Southeast Georgia (1997-2008) ROSTAL, D/C; Georgia Southern University, Statesboro Rostal@georgiasouthern.edu

The gopher tortoise (Gopherus polyphemus) ranges from the southern tip of Florida to the southern coastal plain of South Carolina. No studies have attempted to see how temperatures in field nests fluctuate across the season or between years in this species. The gopher tortoise is restricted to upland habitats and lays hardshelled eggs which require low moisture. HOBO temperature dataloggers were placed in 64 gopher tortoise nests from 1997 to 2008 on Fort Stewart Army Reservation (FSAR). The gopher tortoise population on FSAR is estimated between 3-5,000 individuals. The population displays high reproductive output with high hatching success. On average 6.4 nests were located per year throughout the study. Mean clutch size is 7 eggs. Approximately 28 hatchlings per year were produced from the research nests for a total of 281 hatchlings. No nests were located in year 2000 and 2004. Nests were collected around August 20th each year prior to the earliest hatching observed in the field. Hatchlings were presumed to have completed sex determination prior to this date of nest collection during July based on staging studies conducted in the laboratory . Incubation was completed in the lab at 28 C. All hatchlings were reared in captivity and sexed using laparoscopy. Field nests results were compared with datalogger results from the same habitat to determine the suitability of monitoring ground temperature. Adult male to female sex ratios for gopher tortoises on FSAR is 1:1.14 (n = 485). Mixed sex ratios were observed in many nests while other nests displayed 100 percent male or female hatchlings. Years varied from being male biased to female biased depending on environmental conditions. The cumulative hatchling male to female sex ratio for 1997 to 2008 was 1:0.94.