Estimating the Sex Ratio of Adult Olive Ridley Turtles in the Mexican Pacific: A Biometric Study

Martín-Del-campo R.; Bielli A.; Ortega-Ortiz C.D.; Sosa-Cornejo I.; Petatán-Ramírez D.; González-Camacho Z.B.; Merchant-Larios H. · Herpetological Conservation and Biology (2024)

Resumen

Information on male sea turtles is important, yet scarce, due to the difficulty in accessing them. For sea turtles, tail length is an important secondary sexual characteristic in adults and can be helpful for demographic research. Here, we measured curved carapace length (CCL), curved carapace width (CCW), plastron to tip total tail length (TTL), and cloaca to tip tail length (CTTL) of presumed male and female Olive Ridley Sea Turtles (Lepidochelys olivacea) to determine maturity stages. We studied 106 nesting females on a solitary nesting beach and 94 turtles captured offshore. Based on CCL (58.5–78 cm) and TTL (6.5–20 cm) data from nesting females, we inferred the maturity stage and the individual sex of the turtles captured offshore. Of all individuals captured offshore, 31.9% were presumed males (minimum CCL of 58.5 cm and average TTL of 27.8 cm), 36.2% presumed females, and 31.9% immature. This corresponds to a 1.1F:1.0M adult sex ratio. This finding is consistent with the previously reported sex ratio of Olive Ridley adults from the Costa Rican offshore population; however, it contrasts with earlier studies on hatchlings from Mexico reporting a strong female bias (1.4F:1.0M) likely induced by increasing incubation temperatures due to climate change. Our results highlight the ecological importance of investigating Olive Ridley adult sex ratio and its relationship with hatchling sex ratio, as it may affect the fitness of Olive Ridley turtles and their resilience to climate change.