Sex determination of green turtle, Chelonia mydas, related with nest temperature

Abstract

We could find a seasonal change of sex ratio with an air temperature by examining sex of 443 dead bodies among hatchlings of green turtle, Chelonia mydas, collected from October 1998 to October 1999 on the Khram Island, Thailand. A percent female was under 50% at an air temperature below about 28℃. Sand temperatures beside three nests were recorded by data loggers. As compared with indexes among Yntema (1979), Mtasuzawa (1998) and our two ideas, we proposed our index as a reference incubation temperature, because of easy calculating the index and having a hatching process to differentiate into each sex. The index is an average daily sand temperature in a period from nesting day to the metabolic heating day. Effect of shade by a plastic net over four nests to a percent female was examined. A percent female (30-100%) under shade was lower than that (100%) under sunshine.