ESTES, J.*; WIBBELS, T.; BALAZS, G.; Univ. of Alabama, Birmingham; Univ. of Alabama, Birmingham; National Marine Fisheries Service, Honolulu, Hawaii: Evaluation of incubation temperatures in green turtle nests at French Frigate Shoals, northwest Hawaiian Islands.

The green sea turtle, Chelonia mydas, possesses temperature-dependent sex determination (TSD) in which the incubation temperature of the egg determines the sex of the hatchling. This form of sex determination is of evolutionary significance because it has the potential of producing a wide variety of sex ratios that do not always conform to a 1:1 sex ratio. Hatchling sex ratios resulting from TSD are also of conservational and ecological interest, since they can affect the recovery of endangered populations. French Frigate Shoals (FFS) is an atoll located approximately 800 km northwest of Oahu in the Hawaiian Archipelago. Over 90% of Hawaiian green turtle nesting occurs on FFS. The purpose of this study was to evaluate nest temperatures in an effort to estimate sex ratios. Sand and nest temperatures were monitored on FFS during the 1998-2002 nesting seasons. The average incubation temperatures during the middle third of incubation were used to predict sex ratios. The pivotal temperature of sex determination for Hawaiian green turtles is unknown. If the pivotal for Hawaiian green turtles is similar to that of green turtles in Suriname and Costa Rica, where the pivotal temperatures have been estimated, then the majority of temperatures recorded in this study would be below the pivotal. This would suggest an overall male-bias. Alternatively, the Hawaiian green turtles may have evolved a lower pivotal temperature, which could result in unbiased or even female-biased sex ratios at these temperatures.