Effect of egg location and respiratory gas concentrations on developmental success in nests of the leatherback turtle, Dermochelys coriacea

Hatching success of leatherback turtles, Dermochelys coriacea, is typically ~50%, but the reasons for embryonic death are unknown. We investigated the distribution of egg failure within 16 developing nests to determine whether spatial position or respiratory environment was associated with embryonic death. We measured oxygen and carbon dioxide partial pressures during incubation to investigate whether any spatial variation in developmental success was associated with regions of hypoxia or hypercapnia. Eggs in the centre of nests had a significantly lower mean hatching success (42.1 ± 7.6%) than eggs in the intermediate (66.1 ± 5.3%) and peripheral (69.8 ± 3.5%) regions. Of those eggs that died, there were no significant differences in the timing of early- and late-stage embryonic death in central (77.6 ± 7.2% early death, 17.3 ± 8.2% late death) and peripheral (80.8 ± 10.1% early death, 14.7 ± 5.8% late death) regions. Oxygen tension in all regions of nests was significantly lower and carbon dioxide tension was significantly higher than in control nests by Day 35 of incubation. Although spatial variation in respiratory gases was detected, it did not appear to explain spatially variable developmental success because late-stage embryonic death did not increase in the central region where oxygen tension was lowest and carbon dioxide tension was highest.