Vegetation cover predicts temperature in nests of the hawksbill sea turtle: implications for beach management and offspring sex ratios

Abstract

Whether a sea turtle embryo develops into a male or a female depends, as with many other reptiles, on the temperature during incubation of the eggs. With sea turtles, warm tempera- tures produce 100% females and, thus, increasing global temperatures have the potential to sig- nificantly alter offspring sex ratios. Nest-site selection provides a potential mechanism by which females might adjust the sex of their offspring, but necessitates a reliable cue which provides information about the thermal properties of a nest. Overstory vegetation cover was found to sig- nificantly predict temperatures in nests of the hawksbill sea turtle Eretmochelys imbricata. Nests placed under high vegetation cover are significantly cooler and remain within the male-producing range of temperatures throughout incubation. Interestingly, metabolic heating of the developing clutch is less pronounced under vegetation, further reinforcing the importance of this nesting habitat with respect to the production of males. This underscores the importance of preserving natural vegetation cover at hawksbill nesting beaches in order to maintain the thermal diversity of nesting sites and, potentially, mitigate the impacts of increasing global temperatures.