Physical Parameters Affecting Incubating Temperatures in Loggerhead Sea Turtles, Caretta caretta, in Virginia

Detailed physical profile of eight transplanted loggerhead sea turtle, Caretta caretta, nests were obtained from Virginia and northeastern North Carolina and reburied in Back Bay National Wildlife Refuge (BBNWR), Virginia Beach, Virginia during the summers of 1987, \u2788, and \u2789 to determine if the physical location of the egg within the nest had an affect on sex determination. Transplanted nests were reburied in sandy substrate at a depth of 15-60 em on south facing dunes, and a Campbell Scientific data-logger logged synchronously environmental data. The following data were collected: temperatures at various locations within a nest, net absorbed radiation, ambient temperature, rainfall (em), substrate moisture content, and tide cycles. To understand the determination of sex, a time series analyses was employed to explain the variability, the periodicity, and the irregular oscillations of the temperature data. The regression analysis, using the periodicity of the spring/neap cycles, indicated a significant diurnal and spring/neap tidal affect. The 29.5 and 14.7 day cycle were significant. In addition, a delayed heating affect on the dune temperatures was noted 3-5 days after the lowest tides of the full and new moon cycles which consistently occurred at approximately 3:00P.M. Temperature records in nests at BBNWR were consistent with those producing a predominance of male hatchlings (\u3c28.0C). Temperatures which produced females did exist, but were infrequent. Maximum beach face heating resulted in elevating · temperatures from 1-3C at the 37cm depths. This affect could produce females in late summer and early fall. Physical parameters varied with depth, time of day, and season (summer/fall). The results of this study are important to conservation of sea turtles because they contribute much to the knowledge of how nest manipulation may control sex ratios. Using the approach developed in this study, a mathematical model to predict sex ratios could be developed that would be applicable for various physical regimes found on most major nesting beaches of various sea turtles around the world