ESR 3:305-312 (2007)  -  DOI: https://doi.org/10.3354/esr00058

ABSTRACT: Adult sex ratio is a crucial parameter in population dynamics, with environmental sex determination being of particularly high theoretical and conservation interest. Monitoring hatchling sex ratio over time and space and understanding its variation may prove essential for effective conservation of populations of species with temperature-dependent sex determination. We used clutch incubation duration to estimate sex ratio of hatchlings produced on Zakynthos (Greece), the largest rookery of loggerhead sea turtles Caretta caretta (a species with temperature-dependent sex determination: colder temperatures producing more males) in the Mediterranean. We also explored spatial variation in hatchling sex ratio estimates within this nesting area. The estimated hatchling sex ratio on Zakynthos was female-biased in 2002 and 2003 (68 and 75% females estimated, respectively). We found significant differences in incubation durations between the 6 nesting beaches of Zakynthos, which result in pronounced differences in estimated hatchling sex ratio. Little is known about the relationship between adult and hatchling sex ratio or about the minimum number of males needed in healthy sea turtle populations. With global climate change, however, particular attention should be paid to the protection of the beaches that are apparently characterised by comparatively cold incubation temperatures to provide females with a variety of incubation environments.

KEY WORDS: Caretta caretta · Incubation duration · Loggerhead sea turtle · Mediterranean · Temperature-dependent sex determination