GEIS, A.*; WIBBELS, T.; M�RQUEZ-M, R.; GARDU-O-D, M.; BURCHFIELD, P.; PE-A-V, J.: Evaluation of hatchling Kemp’s ridley sex ratios using nest incubation temperatures at Rancho Nuevo, Mexico

The Kemp’s ridley sea turtle, Lepidochelys kempi, is the most endangered sea turtle in the world. It possesses temperature-dependent sex determination (TSD) in which the incubation temperature of the egg determines the sex of the hatchling. Past studies have suggested that TSD has the potential of producing highly biased sex ratios, which may not be advantageous to the recovery of endangered sea turtle populations. Therefore, it is of great importance to monitor hatchling sex ratio production in nesting beach conservation programs. The primary nesting grounds of the Kemp’s ridley is located on a stretch of beach near Rancho Nuevo, Mexico, where an international conservation effort (coordinated by Instituto Nacional de la Pesca) monitors all nesting and relocates all nests to protected areas (i.e. egg corrals). During the current study, nest temperatures were monitored in relatively large numbers of nests over three nesting seasons (1998-2000). This included monitoring nests in three different egg corrals throughout each of the nesting seasons. Temperature data from the initial two years of this study suggest that a majority of the nests produced mostly or all females, indicating an overall female bias for the 1998 and 1999 nesting seasons. We are currently analyzing the data from the 2000 nesting season. The biased sex ratios predicted during the current study exemplify the need to monitor hatchling sex ratios produced in sea turtle conservation programs. Such information is a prerequisite to the development of effective management strategy for endangered populations.