Sex Ratio of Green Turtle (Chelonia mydas) Hatchlings at Sugozu, Turkey: Higher Accuracy with Pivotal Incubation Duration

Abstract

The majority of green turtle (Chelonia mydas) nests in the Mediterranean basin are found on the eastern Mediterranean beaches of Turkey. There are relatively few studies on the sex ratio of green turtle hatchlings for Turkey. In this study, 12 nests on the Sugozu beaches were equipped with temperature data-loggers during the nesting seasons of 2008 and 2009. Temperatures for the entire incubation period and for the middle third were close to the pivotal temperature around 29.0 degrees C. The average incubation duration for nests with known temperature was 52.8 d. An assessment of incubation durations together with histological analysis of 188 gonad samples collected from 103 nests revealed a pivotal incubation duration of 54.3 d and constant temperature equivalent conversion revealed 54 d. This value was identified for the first time for green turtles on the beaches of the eastern Mediterranean in Turkey based on 196 nests with known incubation duration; these nests showed a female-biased sex ratio in 2008 and 2009 (with 54.9% and 56.5%, respectively). Using incubation duration can increase sample size and therefore accuracy of sex ratio predictions without any hatchling sacrifice.