The influence of incubation duration and clutch relocation on hatchling morphology and locomotor performances of green turtle (Chelonia mydas)

The carapacial scute pattern of sea turtles is a conserved trait that provides taxonomic information. But non-modal scute patterns (NMSPs), i.e. intraspecific individual variabilities, are observed for almost all species and occur relatively often, particularly in hatchlings. We surveyed 67 nests from 61 nesting green turtle females (Chelonia mydas) over an eight-week study duration on Redang Island, Malaysia. During this study, eight NMSP females laid two different clutches. For all newly emerged hatchlings from each nest (n = 4386), we analyzed their scute pattern (i.e. the number of vertebral and costal scutes). For a subsample of 1144 hatchlings, we compared their carapace size, weight, and their locomotor performances (self-righting ability, running and swimming speeds). The proportion of hatchlings with NMSP varied from 0 to 70.4% (mean ± SD = 16.4% ± 16.2) per nest. We compared the scute pattern of nesting females to that of their hatchlings and found that the scute pattern of the mother does not predestine that of her descendants. However, our results revealed that the main driver of scute pattern abnormalities and hatching success was the shorter incubation duration (i.e. warmer incubation temperatures). Eggs hatched after a short incubation period have lowered hatching success. Our data showed also that relocated nests have a greater proportion of NMSP hatchlings compared to in situ nest. Conversely, the scute pattern and clutch relocation do not appear to be linked to lower hatching success or slower locomotor speeds. Our work highlights the effects of incubation duration and clutch relocation techniques on the morphology and survival of green turtle and contributes to better informed management strategies as part of global research efforts to preserve an endangered species. Based on our findings, we suggest strictly following guidelines for relocating a sea turtle nest and applying clutch relocation to populations where hatching success is very low or only as a last resort for doomed nests.