Influence of sand grain size on the nest escape of green sea turtle hatchlings

Abstract

Sea turtle hatchlings rely on their finite energy reserve to sustain embryonic development in underground nests and during the first few days of their post-hatch life, including nest escape, beach crossing, and swimming offshore. This study aimed to investigate if the grain size of the nest substrate has an impact on green sea turtle (Chelonia mydas) hatchlings’ energy usage during nest escape. About-to-hatch green sea turtle eggs were incubated in laboratory chambers filled with either coarse-grain sand (φ = 0.507 phi) or fine-grain sand (φ = 2.028) at a temperature of 28oC. Open-flow respirometry was used to measure the hatchlings’ oxygen consumption rate during nest escape, which was then converted to energy consumption values. Results showed that hatchling morphology, hatching success, emergence success, and synchronous emergence rate were not significantly different between the groups of hatchlings in coarse versus fine sand. Hatchlings that dug through coarse sand emerged significantly faster (168 ± 13.9 h) than those in fine sand (233.21 ± 12.6 h) (t (26) = –3.473, p = 0.002). Additionally, the hatchlings in coarse sand (310.55 ± 28.1 kJ) consumed significantly less energy than hatchlings in fine sand (474.85 ± 64.7 kJ) (t (17.739) = –2.328, p = 0.032). A difference in amount of energy reserve upon emergence was detected between coarse and fine sand groups. To improve hatchery management practices, relocating “doomed” clutches into coarse sand (φ = 0.507) could potentially maximise the hatchlings’ energy reserve.