WOODS, Caroline S.*; ROSTAL, David C.; Georgia Southern University: Identifying Sex in Juvenile and Immature Gopher Tortoises Gopherus polyphemus, a Species with Delayed Sexual Maturation

The presence of temperature-dependent sex determination and the delayed expression of secondary sex characteristics (13 to 20 years) in gopher tortoises have made determining population demographics difficult. The use of steroids to determine sex in juvenile and immature gopher tortoises was validated in this study. The goal was to accurately determine the sex (and subsequent sex ratios) of immature gopher tortoises. A captive population of immature tortoises raised from hatching was used to validate the procedure. These tortoises were laparoscoped first to determine sex. Blood samples were then drawn and levels of testosterone (T) and estradiol (E₂) were measured using an Enzyme-linked Immunosorbent Assay (ELISA). Sex determined from the steroid levels was then compared with the known sex determined by laparoscopy. Results show that a combination of T and E₂ can be used to accurately verify the sex of immature gopher tortoises. T was observed to rise significantly in males once they reached 18 cm straight carapace length (SCL). Below 18 cm SCL, sex was only distinguishable using a combination of T and E₂. Wild tortoises from two large populations (Fort Stewart Army Installation, GA and Merritt Island National Wildlife Refuge, FL) were also used for this. Tortoises were hand captured and blood was drawn within the first 15 minutes to avoid stress effect on the steroid levels. T and E₂ were measured for the wild tortoises. This data was then used to establish the sex ratios for juvenile and immature tortoises in the two wild populations. These sex ratios will be compared to the adult sex ratios that have been observed and to temperature profiles from field nests.