LEBLANC, A.M.**; ROSTAL, D.C.; WIBBELS, T.; Univ. of Alabama, Birmingham; Georgia Southern Univ.; Univ. of Alabama, Birmingham: Predicting loggerhead sex ratios: confounding effects of temperature variation and thermosensitive period

Temperature-dependent sex determination was studied in loggerhead sea turtles (Caretta caretta) nesting on Wassaw (2000-2004) and Blackbeard Island (2001-2004) NWRs in Georgia. Sex ratios were estimated for 18 nests using histological analysis of gonadal tissue from 10 hatchings per nest. Each nest contained a temperature data logger. The temperature and sex ratio data were used to estimate a “natural” pivotal temperature and transitional range of temperatures (TRT). For these natural nests which did not experience rain events during the thermosensitive period, the natural pivotal temperature was estimated to be 29.3°C and the TRT was estimated to be 28.7-30.1°C. These estimates were similar to previously published pivotal temperature for Atlantic loggerheads based on constant incubation temperatures. Sex ratios varied widely in nests experiencing temperatures near the pivotal. This may be due to factors such as variation in pivotal temperature between clutches and fluctuation in daily temperature (especially from rain events). The temperature and sex ratio data were also used to evaluate the thermosensitive period by altering its predicted length and timing in order to determine a best-fit model for predicting sex ratios. The sex ratio data from the 18 nests indicate that both male and female hatchlings were produced with a yearly range of 60-85% female. However, this female bias is significantly less than those reported for nesting beaches in Florida. Therefore, Georgia beaches may be of conservational significance due to the increased production of males.