ESTIMATING SEX-RATIOS OF LOGGERHEAD TURTLES IN BRAZIL FROM PIVOTAL INCUBATION DURATIONS

A method of estimating natural sex ratios of hatchlings of species wit h temperature-dependent sexual differentiation from data on incubation durations is described. The method was applied to loggerhead turtles (Caretta caretta) nesting in Brazil. Data on incubation durations were collected from 11 nesting beaches monitored for up to six seasons. It was estimated that 82.5% of the loggerhead hatchlings produced were f emale. The strongly female-biased sex ratio in Brazil is similar to th at found previously for loggerheads using beaches in the eastern U.S.A . This suggests that a female-biased hatchling sex ratio may be a feat ure of loggerhead populations.