Hydric environment and sex determination in the flatback turtle (Natator depressus Garman) (Chelonia : Cheloniidae)

Abstract

Eggs of Natator depressus (from eastern Queensland, Australia) were incubated at a constant temperature of 29.5˚C on vermiculite substrate with three different moisture levels: wet (~–180 kPa), intermediate (~–1200 kPa) and dry (~–2000 kPa). The male : female ratios on wet, intermediate and dry substrates were 8 : 7, 5 : 5 and 5 : 8 respectively. Sex determination was not influenced by the hydric environment but was significantly affected by different clutches. A clutch with smaller eggs appeared to produce a higher proportion of females. The pivotal temperature was close to 29.5˚C, with a possibly narrow transitional temperature range of 1˚C. Visual designation of sex was confirmed (100%) by histological examination. Hatching success and the incubation duration were not influenced by the hydric environment.