Effectiveness of shading to mitigate the impact of high temperature on sea turtle clutches considering the effect on pri
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Effectiveness of shading to mitigate the impact of high temperature on sea turtle clutches considering the effect on primary sex ratios José Vindas-Picado 1 & Adam Yaney-Keller 2 & Laura St. Andrews 2,3 & Aliki Panagopoulou 2 & Pilar Santidrián Tomillo 2 Received: 30 January 2020 / Accepted: 9 September 2020/ # Springer Nature B.V. 2020
Abstract
Developmental success of sea turtle clutches depends on incubation temperature, which also determines sex ratio of hatchlings. As global temperatures are rising, several studies have proposed mitigation strategies such as irrigation and shading to increase hatching success. Our study expands upon this research and measures the effects of using boxes with different degrees of shade coverage (50%, 80%, and 90%) on sand temperature and water content. Boxes were fully covered with fabric in 2017/2018 (top and sides) but were side open in 2018/2019. We took measurements at olive ridley (Lepidochelys olivacea) and leatherback (Dermochelys coriacea) turtle nest depths (45 and 75 cm) at Playa Grande, Costa Rica. Shading reduced temperature by up to 0.8 °C and up to 0.4 °C at 45 cm and 75 cm, respectively. There were statistically significant differences between shading and control treatments at both depths, but differences between shade treatments were only significant when using side open boxes, possibly due to air flow. Shading had no effect on water content. While the impact of using shaded boxes on temperature was low, the potential impact on primary sex ratios was large. If shading were applied to leatherback clutches, the percentage of female hatchlings could vary by up to 50%, with a maximum difference around the pivotal temperature (temperature with 1:1 sex ratio). Shading can be useful to increase hatching success, but we recommend avoiding it at temperatures within the transitional range (temperatures that produce both sexes), or using it only during the last third of incubation, when sex is already determined. As global warming will likely continue, understanding potential impact and effectiveness of mitigation strategies may be critical for the survival of threatened sea turtle populations. Keywords Climate mitigation . Climate change . Hatchery . Hatching success . TSD
* Pilar Santidrián Tomillo [email protected] Extended author information available on the last page of the article
Mitigation and Adaptation Strategies for Global Change
1 Introduction Climate change affects organisms and biological processes both on land (Walther et al. 2002) and in the ocean (Hoegh-Guldberg et al. 2007; Poloczanska et al. 2013). Sea turtles are affected by variations in thermal conditions in different ways. In particular on the beach, sand temperatures affect the duration of the incubation period (Valverde et al. 2010), hatching and emergence success (Santidrián Tomillo et al. 2009), and sex ratio of hatchlings as sea turtles have temperature-dependent sex determination (TSD) (Standora and Spotila 1985; Yntema and Mrosovsky 1982). Embryonic development is generally delimited t
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