ESR 8:147-155 (2009)  -  DOI: https://doi.org/10.3354/esr00200

Methods of estimating natural sex ratios of sea turtles from incubation temperatures and laboratory data

N. Mrosovsky1,*, S. J. Kamel2, C. E. Diez3, R. P. van Dam4

1Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario M5S 3G5, Canada
2College of Biological Sciences, Section of Evolution and Ecology, University of California at Davis, Davis, California 95616, USA
3Departamento de Recursos Naturales y Ambientales, PO Box 366147, San Juan, Puerto Rico 00936, USA
4Chelonia, PO Box 9020708, San Juan, Puerto Rico 00902, USA

ABSTRACT: In laboratory experiments, we determined pivotal temperature (29.6°C), i.e. the constant temperature yielding 50% of each sex, and pivotal incubation duration (57.3 d) for hawksbill turtles Eretmochelys imbricata (Agassiz, 1857) nesting on Mona Island, Puerto Rico. Based on the laboratory curves for sex ratio, predictions were made about sex ratio in field conditions. Temperature of natural nests provided a better prediction of the actual independently verified sex ratios than incubation duration. Predictions made from temperature were not highly sensitive to the exact specification of the thermosensitive period within incubation. Recommendations are made for estimating sex ratios of hatchlings on beaches for which there is currently no information. The pivotal temperatures for Mona Island hawksbill turtles were similar to those obtained previously for hawksbills nesting in Antigua and in Brazil, suggesting some conservatism in this characteristic. If pivotal temperatures are similar for different areas, then sex ratios of turtles hatching on thermally different beaches are likely to vary considerably. Implications for the impacts of global warming on sea turtles are also discussed.


KEY WORDS: Hawksbill · Sea turtle · Sex ratio · Temperature · Incubation duration


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Cite this article as: Mrosovsky N, Kamel SJ, Diez CE, van Dam RP (2009) Methods of estimating natural sex ratios of sea turtles from incubation temperatures and laboratory data. Endang Species Res 8:147-155. https://doi.org/10.3354/esr00200

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