Asynchronous Emergence of Flatback Seaturtles, Natator Depressus, from a Beach Hatchery in Northern Australia

Abstract

The timing and synchrony of sea turtle emergences from the nests are primary factors in determining hatchling vigor and likelihood of survival. A clear benefit of synchronous emergence is a reduction in energy expenditure through social facilitation, but disadvantages also result from reduction in energy stores if hatchlings have to wait any appreciable time in the nest. We investigated hatchling emergence times throughout emergence of the entire clutch for 21 clutches of Flatback Seaturtles, Natator depressus, incubating in a beach hatchery at three clutch sizes and three nest depths. Emergence of the entire clutch spanned an average of 3.1 days, with shallower nests exhibiting greater emergence asynchrony (mean20cm = 4.0 days, mean35cm = 4.5 days) than deeper nests (mean50cm = 1.7 days). Hatchlings emerged through the night, peaking between 2100 and 2200 h, with hatchlings from shallower nests emerging earlier in the night. For natural nests, hatchlings generally emerged within a single night, evident from the low number of hatchlings remaining in the nest the day after emergence. The disparate observations between a beach hatchery, and natural nests provide important conservation implications for hatchery management.