Nest depth may not compensate for sex ratio skews caused by climate change in turtles

Read the Commentaries on this Feature Paper: Chelonians in a changing climate: can nest site selection prevent sex ratio skews?; For reptiles with temperature‐dependent sex determination, thermal variability may be as important as thermal averages; Revealing the links between climate and demography for reptiles with environmental sex determination Response from the authors: Experimental field studies of species' responses to climate change: challenges and future directions Maternal ability to match nest characteristics with environmental conditions can influence offspring survival and quality, and may provide a mechanism by which animals can keep pace with climate change. In species with temperature‐dependent sex determination that construct subterranean nests, the depth of the nest may affect incubation temperatures, and thus offspring sex ratio. Maternal adjustment of nest depth may be a mechanism by which climate change‐induced sex ratio skews could be prevented in globally imperiled taxa such as turtles. We experimentally manipulated nest depth within a biologically relevant range in nests of the model turtle species Chrysemys picta. We then quantified the effects of nest depth on incubation regime, offspring sex ratio and offspring performance. We found no effect of nest depth on six parameters of incubation regime, nor on resultant offspring survival, size or sex ratio. However, deeper nests produced hatchlings that weighed less, and were faster at righting themselves and swimming, than hatchlings from shallower nests. We suggest that cues used by females in adjusting nest depth are unreliable as predictors of future incubation conditions, and the adjustment in nest depth required to affect sex ratio in this species may be too great to keep pace with climate change. Therefore, maternal adjustment of nest depth seems unlikely to compensate for climate change‐induced sex ratio skews in small‐bodied, freshwater turtles.