Developmental timing of flash drought influences offspring survival in the field.

Extreme climate events, including rapid-onset flash droughts, are increasing with anthropogenic climate change. Flash droughts impact growth and survival of plants, microbes, and invertebrates, yet less is known about their ecological consequences in vertebrates. Although constant water deprivation during vertebrate embryonic development influences a range of offspring traits, the effects of acute, short-term hydric stress are less well-studied, particularly in the context of subsequent survival in the field. In this study, we combined experimental manipulation in the laboratory with a large-scale field experiment to examine the effects of the developmental timing of flash drought in an oviparous vertebrate model. We exposed common snapping turtle (Chelydra serpentina) eggs to simulated flash drought events at different stages of embryonic development and measured the effects on growth and offspring phenotypes. We then conducted an experimental release in the field to evaluate offspring survival during migration from the nest. Flash drought during mid-to-late development decreased egg mass, incubation time, and hatchling body size, while flash drought during late development substantially limited post-hatching survival in the field. This study is among the first to examine juvenile survival effects of flash drought during embryonic development in a vertebrate system. Our results suggest that early-life mortality is likely to increase as flash droughts intensify with climate change. This study contributes to a growing body of research on the ecological consequences of extreme climate events and highlights the importance of considering these events in a developmental context.