Climate change and temperature‐linked hatchling mortality at a globally important sea turtle nesting site

Abstract

The study of temperature-dependent sex determination (TSD) in vertebrates has attracted major scientific interest. Recently, concerns for species with TSD in a warming world have increased because imbalanced sex ratios could potentially threaten population viability. In contrast, relatively little attention has been given to the direct effects of increased temperatures on successful embryonic development. Using 6603 days of sand temperature data recorded across 6 years at a globally important loggerhead sea turtle rookery-the Cape Verde Islands-we show the effects of warming incubation temperatures on the survival of hatchlings in nests. Incorporating published data (n = 110 data points for three species across 12 sites globally), we show the generality of relationships between hatchling mortality and incubation temperature and hence the broad applicability of our findings to sea turtles in general. We use a mechanistic approach supplemented by empirical data to consider the linked effects of warming temperatures on hatchling output and on sex ratios for these species that exhibit TSD. Our results show that higher temperatures increase the natural growth rate of the population as more females are produced. As a result, we project that numbers of nests at this globally important site will increase by approximately 30% by the year 2100. However, as incubation temperatures near lethal levels, the natural growth rate of the population decreases and the long-term survival of this turtle population is threatened. Our results highlight concerns for species with TSD in a warming world and underline the need for research to extend from a focus on temperature-dependent sex determination to a focus on temperature-linked hatchling mortalities.

Climate change resilience of a globally important sea turtle nesting population

“…As incubation temperatures approach lethal levels, towards the end of the century, growth is expected to reach a plateau, and eventually start to decline. This is in agreement with previous studies, indicating that resilience of TSD species to climate change will eventually be overcome, due to unviable high temperatures (Laloë et al., ; Santidrián Tomillo et al., ). However, the existence of thermal microrefugia can potentially allow for continued population growth.…”

“…We then accounted for the microhabitat‐specific hatchling survival (hatchling emergence success in 2013/2014: open sand = 66.1 ± 30.8%, n = 62; forest border = 51.9 ± 38.3%, n = 20; and forest = 42.2 ± 41.6%, n = 16; Patrício, Marques, et al., ), and the temperature‐induced hatchling mortality per microhabitat, using the logistic equation described in Laloë, Cozens, Renom, Taxonera, and Hays (), which models the relationship between emergence success (E) and incubation temperature (T):where the upper asymptote is A = 86%, the growth rate constant is β = −1.7°C, the inflection point is T 0 = 32.7°C, and T = mean incubation temperature per microhabitat (Laloë et al., ). We could not use the population‐specific hatchling mortality response to incubation temperature as currently natural nests in Poilão experience moderate temperatures (i.e., 27.5–32.2°C for mean incubation temperatures during middle third of incubation, in the centre of the clutch, n = 101, Patrício, Marques, et al., ), not sufficiently high to negatively affect embryo survival.…”

Potential limitations of behavioral plasticity and the role of egg relocation in climate change mitigation for a thermally sensitive endangered species

“…Uncertainty exists regarding the ability of long‐lived thermally sensitive reptiles, such as sea turtles, to exhibit compensatory responses to accelerated climate‐driven environmental changes capable of offsetting negative consequences to population demographics (Hays, Mazaris, Schofield, & Laloë, ; Laloë, Cozens, Renom, Taxonera, & Hays, ). For eastern Pacific hawksbills nesting in mangrove estuaries at Bahía de Jiquilisco, El Salvador, and Estero Padre Ramos, Nicaragua, our results demonstrate that clutches protected in situ incubated at higher temperatures, yielded lower hatching success, produced a higher percentage of female hatchlings, and produced less fit offspring than clutches relocated to hatcheries.…”

Effect of sand granulometry on the egg hatchling success of the sea turtle Caretta caretta

“…Recentes estudos indicam que as mudanças climáticas podem ainda afetar o desenvolvimento embrionário e o sucesso de eclosão dos filhotes (Hawkes et al 2007;Fuentes et al 2011;Laloë et al 2017). A temperatura do ambiente é um fator de grande influência não apenas na sobrevivência dos filhotes, mas exerce um papel determinante na razão sexual das ninhadas de tartarugas marinhas (Mros-ovsky, 1994;Kobayashi et al 2017;Laloë et al 2017). Temperaturas abaixo de 28 °C favorecem filhotes machos; acima de 28 °C favorecem filhotes do sexo feminino; e a temperatura de 28 e 30 °C favorece igualmente ambos os sexos (Ferreira Júnior, 2009a).…”