Scientia Marina, Vol 78, No 2 (2014)

Adult sex ratios of loggerhead sea turtles (Caretta caretta) in two Mediterranean foraging grounds


https://doi.org/10.3989/scimar.03988.30E

Paolo Casale
Department of Biology and Biotechnologies “Charles Darwin”, University of Rome “La Sapienza” - Centre for Ecology and Conservation, University of Exeter, Italy

Daniela Freggi
Sea Turtle Rescue Centre WWF Italy, Italy

Fulvio Maffucci
Stazione Zoologica Anton Dohrn - Dipartimento di Scienze” Università Roma Tre, Italy

Sandra Hochscheid
Stazione Zoologica Anton Dohrn, Italy

Abstract


Sea turtles show temperature-dependent sex determination (TSD) and information on sex ratios at different life stages is necessary both for population dynamics models for conservation and to shed light on the possible adaptive value of TSD. Adults represent the less abundant class of sea turtle populations and adult sex ratios at foraging grounds are very difficult to obtain. We first analysed biometric data of 460 juvenile and adult loggerhead sea turtles ranging from 60 to 97.5 cm curved carapace length (CCL), in which a clear bimodal distribution of tail length (the main secondary sexual character of adult males) was observed in the size class >75 cm CCL. We then sexed 142 adult turtles in this size class collected from the Tunisian shelf and from the southeastern Tyrrhenian Sea, observing a proportion of females of 51.5% (95% CI: 41.2-61.8%; n=97) and 40.0% (95% CI: 25.7-55.7%; n=45) respectively. Our results complement previous studies and support their findings of similar and more balanced sex ratios in adult and juvenile loggerhead turtles in the Mediterranean, in contrast with highly female-biased sex ratios of hatchlings.

Keywords


Caretta caretta; sea turtle; adult; sex ratio; maturity; temperature-dependent sex determination; Mediterranean

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