Pivotal temperatures for loggerhead turtles (Caretta caretta) from northern and southern nesting beaches

Abstract

The pivotal incubation temperature (that giving 50% of each sex) was estimated for two clutches of eggs from loggerhead sea turtles (Caretta caretta) nesting in each of three areas along the east coast of the United States: North Carolina, Georgia, and southern Florida. All pivotal temperatures were close to 29.0 °C. There was a significant difference between the pivotal temperatures of the two clutches from Florida. As an index of beach temperature, data on incubation durations in the three areas were collated and analysed: even during the warmest part of the season, incubation took about 6 days longer in North Carolina than in Georgia, and about 10–14 days longer than in Florida. Since there was no evidence that pivotal temperatures in North Carolina were lower than those of turtles nesting further south, it is likely that a higher percentage of males are produced on the North Carolina beaches, but data on pivotal temperatures of additional clutches are needed before this prediction can be made with confidence. The possible use of incubation duration for estimating sex ratios of hatchlings is discussed.