MEPS 577:189-203 (2017)  -  DOI: https://doi.org/10.3354/meps12242

Balanced primary sex ratios and resilience to climate change in a major sea turtle population

Ana R. Patrício1,2,*, Ana Marques3, Castro Barbosa4, Annette C. Broderick1, Brendan J. Godley1, Lucy A. Hawkes1, Rui Rebelo3, Aissa Regalla4, Paulo Catry2

1Centre for Ecology and Conservation, University of Exeter, TR10 9FE Penryn, UK
2MARE - Marine and Environmental Sciences Centre, ISPA - Instituto Universitário, 1140-041 Lisbon, Portugal
3Centre for Ecology, Evolution and Environmental Changes (CE3C), Faculdade de Ciências, Universidade de Lisboa, Bloco C2, Campo Grande, 1749-016 Lisboa, Portugal
4Institute of Biodiversity and Protected Areas of Guinea-Bissau (IBAP), CP - 70 Bissau, Guinea Bissau
*Corresponding author:

ABSTRACT: Global climate change is expected to have major impacts on biodiversity. Sea turtles have temperature-dependent sex determination, and many populations produce highly female-biased offspring sex ratios, a skew likely to increase further with global warming. We estimated the primary sex ratio at one of the world’s largest green turtle Chelonia mydas rookeries in Guinea-Bissau, West Africa, and explored its resilience to climate change. In 2013 and 2014, we deployed data loggers recording nest (n = 101) and sand (n = 30) temperatures, and identified hatchling sex by histological examination of gonads. A logistic curve was fitted to the data to allow predictions of sex ratio across habitats and through the nesting season. The population-specific pivotal temperature was 29.4°C, with both sexes produced within incubation temperatures from 27.6 to 31.4°C: the transitional range of temperatures (TRT). Primary sex ratio changed from male- to female-biased across relatively small temporal and spatial scales. Overall it was marginally female-biased, but we estimated an exceptionally high male hatchling production of 47.7% (95% CI: 36.7-58.3%) and 44.5% (95% CI: 33.8-55.4%) in 2013 and 2014, respectively. Both the temporal and spatial variation in incubation conditions and the wide range of the TRT suggest resilience and potential for adaptation to climate change if the present nesting habitat remains unchanged. These findings underline the importance of assessing site-specific parameters to understand populations’ responses to climate change, particularly with regard to identifying rookeries with high male hatchling production that may be key for the future conservation of sea turtles under projected global warming scenarios.


KEY WORDS: Sex ratio · Climate change · Green turtle · Chelonia mydas · Pivotal temperature · Transitional range of temperatures · Thermosensitive period


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Cite this article as: Patrício AR, Marques A, Barbosa C, Broderick AC and others (2017) Balanced primary sex ratios and resilience to climate change in a major sea turtle population. Mar Ecol Prog Ser 577:189-203. https://doi.org/10.3354/meps12242

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