Effects of sand erosion and current harvest practices on incubation of the flatback sea turtle (Natator depressus)

A suitable gaseous, hydrous and thermal nest environment is essential for the development of sea turtle embryos. The harvest of partial clutches by indigenous people and changes in nest depth from wind erosion or predation have prompted questions about the impact of clutch size and nest depth on nest success and hatchling output. We investigated the impact of reduced clutch sizes and nest depths on flatback sea turtle (Natator depressus) eggs, using a hatchery on a natural beach and clutch sizes of 10, 30 and 50 eggs, deposited at depths of 25, 35 and 50 cm. Hatchlings were collected on emergence and their size, mass, scalation and locomotor performance were measured. Neither clutch size nor nest depth had a significant effect on hatching success, emergence success or escape success in this study. Smaller clutches had longer incubation durations due to the lower temperatures within the nest, presumably from the lower metabolic heat produced. Hatchlings from deeper nests emerged later in the night than did those from shallower nests. Within the context of this study, changes to clutch size and nest depth appear to have no detrimental effect on the fate of the remaining eggs and the condition and performance of hatchlings.