Effects of Nest Depth, Shading, and Metabolic Heating on Nest Temperatures in Sea Turtle Hatcheries

Abstract

This study investigated the effects of hatchery shading, nest depth, and metabolic heating on the temperature of Chelonia mydas clutches incubated in hatcheries at Ma'Daerah, Terengganu, Malaysia. Metabolic heating was found to be the most influential factor on nest temperature; the number of completely developed eggs explained nearly half of the variation in mean nest temperature. The degree of hatchery shading (70% vs. 100%) and nest depth (50 vs. 75 cm) had little influence on nest temperatures, with mean nest temperatures between 28° and 28.6°C in the first third of incubation (before metabolic heating of the clutch began to have an effect). Nests at a depth of 75 cm had significantly lower daily temperature ranges than nests at a depth of 50 cm, but a maximum mean daily range of 0.5°C (50 cm depth in 70% shade hatchery) resulted in calculated constant temperature equivalents (CTE) being identical to observed mean nest temperatures. The results of this study indicate that, under current climatic conditions in this area, shading between 70% and 100% and nest depths between 50 and 75 cm will incubate green turtle clutches within the optimal temperature range for development. However, this information is site-specific and could vary significantly between locations due to the complex interaction of biological, chemical, and physical factors that influence sea turtle nest temperature.