Loggerhead turtle--Breeding

Sea turtles have temperature-dependent sex determination, with males being produced at cooler temperatures and females at warmer ones. Thus, sex ratios are often estimated on average nest temperatures, but this is unreliable. Therefore, many studies have begun to look to alternative methods to identify sex ratios. Other methods used to determine sex require hatchling sacrifice or are labor intensive. This study utilized high performance liquid chromatography (HPLC) to investigate correlations between steroid hormone levels in hatchling plasma and allantoic fluid, nest temperature and sex. Hatchling sex was determined laparoscopically to ground-truth hormone profiles. No correlation was found between hormones, nest temperature and sex. However, as hormones were readily detectable by HPLC, the technique may be applicable to juvenile or adult turtles with mature profiles.

The sex ratios of hatchling loggerheads (Caretta caretta) were determined to provide robust assessments of regional and seasonal contributions of males and females to the population. Hatchlings from nests along the Atlantic coastline were raised to 120 g, sexed laparoscopically and verified histologically. Sex ratios differed at the beach, subseason, and subpopulation levels. There was no difference in overall sex ratios between the two study years. Average nest temperature and incubation durations were not accurate sex ratio correlates. Temperatures that produced female biased or male biased sex ratios overlapped in ranges with those producing a single sex. I found that the Transitional Range of Temperatures for loggerhead sea turtles is approximately 26.5°C--32°C, and the best correlation between average temperature and sex ratio occurred at 50--65% of incubation. Further studies are needed to define the roles of other environmental factors or the responses of tissues in loggerhead sex determination.