Mitigating the effects of climate change on the nests of sea turtles with artificial irrigation.

For sea turtles, like many oviparous species, increasing temperatures during development threaten to increase embryonic mortality, alter offspring quality, and potentially create suboptimal primary sex ratios. Various methods are being implemented to mitigate the effects of climate change on reproductive success, but these methods, such as breeding programs, translocations, and shading, are often invasive and expensive. Irrigation is an alternative strategy for cooling nests that, depending on location, can be implemented relatively quickly and cheaply. However, multiple factors, including ambient conditions, nest substrate, and species characteristics, can influence irrigation success. Additionally, irrigation can vary in duration, frequency, and the volume of water applied to nests, which influences the cooling achieved and embryonic survival. Thus, it is critical to understand how to maximize cooling and manage risks before implementing irrigation as a nest-cooling strategy. We reviewed the literature on nest irrigation to examine whether artificial irrigation is feasible as a population management tool. Key factors that affected cooling were the volume of water applied and the frequency of applications. Embryonic responses varied with species, ambient conditions, and the timing of irrigation during development. Nest inundation was the key risk to a successful irrigation regime. Future irrigation regimes must identify clear targets, either primary or adult sex ratios, that maximize population viability. Monitoring population responses and adjusting the irrigation regime in response to population characteristics will be critical. Most studies reported on the manipulation of only one or two variables, further research is required to understand how altering multiple factors in an irrigation regime influences the cooling achieved and embryonic responses.

Como sucede con muchas especies ovíparas, el incremento en las temperaturas durante el desarrollo embrionario puede aumentar la mortalidad embrionaria, alterar la calidad de la descendencia y tiene el potencial de crear proporciones sexuales primarias poco óptimas en las tortugas marinas. Se están implementando varios métodos para mitigar los efectos del cambio climático sobre el éxito reproductivo, aunque dichos métodos (p. ej.: los programas de reproducción, reubicaciones y sombreado) suelen ser invasivos y costosos. La irrigación es una estrategia alternativa para el enfriamiento de los nidos, la cual, según la ubicación, puede implementarse de manera rápida y económica. Sin embargo, factores como las condiciones ambientales, el sustrato de anidación y las características de la especie pueden influir sobre el éxito de la irrigación. Además, la duración, frecuencia y volumen del agua aplicada a los nidos durante la irrigación puede variar, lo que influye sobre el enfriamiento y la supervivencia embrionaria. Por todo esto, es importante entender cómo maximizar el enfriamiento y gestionar los riesgos antes de implementar la irrigación como estrategia de enfriamiento de nidos. Revisamos la literatura sobre la irrigación de nidos para analizar si la irrigación artificial es una herramienta viable de manejo poblacional. Los factores clave que afectaron el enfriamiento fueron el volumen aplicado de agua y la frecuencia de las aplicaciones. Las respuestas embrionarias variaron según la especie, condiciones ambientales y el momento de irrigación durante el desarrollo. El principal riesgo para un régimen exitoso de irrigación fue la inundación del nido. Los próximos regímenes de irrigación deben identificar objetivos claros, ya sean las proporciones sexuales adultas o primarias, que maximicen la viabilidad poblacional. Para esto, serán muy importantes el monitoreo de las respuestas poblacionales y el ajuste del régimen de irrigación en respuesta a las características de la población. La mayoría de los estudios reportaron la manipulación de una o dos variables, por lo que se requiere de mayores estudios para entender cómo la alteración de varios factores en el régimen de irrigación influye sobre el enfriamiento obtenido y las respuestas embrionarias.

Ontogeny and ecological significance of metabolic rates in sea turtle hatchlings.

BACKGROUND: Sea turtle hatchlings must avoid numerous predators during dispersal from their nesting beaches to foraging grounds. Hatchlings minimise time spent in predator-dense neritic waters by swimming almost continuously for approximately the first 24 h post-emergence, termed the 'frenzy'. Post-frenzy, hatchling activity gradually declines as they swim in less predator-dense pelagic waters. It is well documented that hatchlings exhibit elevated metabolic rates during the frenzy to power their almost continuous swimming, but studies on post-frenzy MRs are sparse. RESULTS: We measured the frenzy and post-frenzy oxygen consumption of hatchlings of five species of sea turtle at different activity levels and ages to compare the ontogeny of mass-specific hatchling metabolic rates. Maximal metabolic rates were always higher than resting metabolic rates, but metabolic rates during routine swimming resembled resting metabolic rates in leatherback turtle hatchlings during the frenzy and post-frenzy, and in loggerhead hatchlings during the post-frenzy. Crawling metabolic rates did not differ among species, but green turtles had the highest metabolic rates during frenzy and post-frenzy swimming. CONCLUSIONS: Differences in metabolic rate reflect the varying dispersal stratagems of each species and have important implications for dispersal ability, yolk consumption and survival. Our results provide the foundations for links between the physiology and ecology of dispersal of sea turtles.

A review of the effects of incubation conditions on hatchling phenotypes in non-squamate reptiles.

Developing embryos of oviparous reptiles show substantial plasticity in their responses to environmental conditions during incubation, which can include altered sex ratios, morphology, locomotor performance and hatching success. While recent research and reviews have focused on temperature during incubation, emerging evidence suggests other environmental variables are also important in determining hatchling phenotypes. Understanding how the external environment influences development is important for species management and requires identifying how environmental variables exert their effects individually, and how they interact to affect developing embryos. To address this knowledge gap, we review the literature on phenotypic responses in oviparous non-squamate (i.e., turtles, crocodilians and tuataras) reptile hatchlings to temperature, moisture, oxygen concentration and salinity. We examine how these variables influence one another and consider how changes in each variable alters incubation conditions and thus, hatchling phenotypes. We explore how incubation conditions drive variation in hatchling phenotypes and influence adult populations. Finally, we highlight knowledge gaps and suggest future research directions.

Sea turtle hatchling locomotor performance: incubation moisture effects, ontogeny and species-specific patterns.

Incubation conditions are critical in determining numerous traits in reptilian neonates. This is particularly significant in species with low offspring survival such as sea turtle species, because of the extremely high predation rates that hatchlings face during their initial dispersal from nesting beaches. Hatchlings that develop in suboptimal nest environments are likely to be smaller, slower and more susceptible to predation than hatchlings from optimal nest environments. Previous studies have focused on the effects of temperature on hatchling traits, but few have investigated the effects of moisture concentrations, despite moisture levels in nests influencing hatchling size, sex, incubation duration, and hatching success. Here, we incubated eggs of three sea turtle species at various moisture levels and tested the terrestrial and aquatic locomotor performance of the resultant hatchlings during the frenzy and post-frenzy period. We also compared and evaluated the ontogeny of early locomotor performance for each species over the first months of life. Drier incubation conditions produced hatchlings that crawled more slowly and took longer to self-right than hatchlings from wetter incubation conditions. There was no difference in swimming performance associated with moisture treatments. We suggest that moisture in the nest environment during incubation may influence hatchling performance via their initial hydration levels. Thus, nest moisture influences terrestrial performance (i.e., escaping from the nest and dispersing across the beach), although upon entering the ocean hatchlings have the opportunity to rehydrate by drinking and thus, differences in locomotor performance associated with moisture treatments cease.