Sex-dependent phenological plasticity in an arctic hibernator

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Hibernation allows animals to conserve energy during predictable seasonal intervals of low resource availability. However, many organisms now face rapid changes in the temporal distribution of resources and their capacity to plastically adjust the timing of key seasonal life-cycle events, including hibernation, is likely a critical aspect of individual and population resilience to climate change. For vertebrates, one of the most commonly reported consequence of climate change involves warmer spring temperatures leading to earlier timing, although climate-driven changes in precipitation patterns can also alter the temperature dependency of phenology. For example, in the Arctic, higher spring temperatures are associated with increased intensity and frequency of late season snow events and have resulted delayed environmental phenology. The degree to which mammals can prolong the expression of seasonal dormancy is unclear. Here, we show that arctic ground squirrels exhibit sex-dependent plasticity in the physiology and phenology of hibernation in response to late spring snowstorms. Females and non-reproductive males responded to a >1 month delay in snow melt by extending heterothermy or re-entering hibernation after several days of euthermy, leading to a 2-week delay in reproduction. Extended hibernation consisted of repeated short 2-3 day torpor bouts with a slightly elevated minimum body temperature during torpor. In contrast, reproductive males did not extend or re-enter hibernation because this is prevented by seasonal gonadal recrudescence. Our findings reveal intriguing differences in how males and females respond to climatic stressors which may lead to phenological mismatches between the sexes.

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