Integrating mortality risks and theadaptiveness of hibernation

International audienceLow mortality rate is often associated with slow life history, and so far, has mainly been assessed through examinations of specificadaptations and lifestyles that limit mortality risk. However, the organization of activity time budgets also needs to beconsidered, since some activities and the time afforded for performing them may expose animals to higher mortality risks such asincreased predation and/or increased metabolic stress, including oxidative stress. We examined the extent of activity timebudgets contribution to explaining variation in life history traits in mammals. We specifically focused on hibernating speciesbecause of their marked seasonal cycle of activity/inactivity associated with very different mortality risks. Hibernation isconsidered a seasonal adaptation to prolonged periods of food shortage and cold. This inactivity period may also reduce bothextrinsic and intrinsic mortality risks, by decreasing exposure to predators and drastically reducing metabolic rate. In turn,reduction in mortality may explain why hibernators have slower life history traits than non-hibernators of the same size. Usingphylogenetically controlled models, we tested the hypothesis that longevity was positively correlated with the hibernation seasonduration (the time spent between immergence and emergence from the hibernaculum or den) across 82 different mammal species.We found that longevity increased significantly with hibernation season duration, an effect that was particularly strong in smallhibernators (< 1.5kg) especially for bats. These results confirm that hibernation not only allows mammals to survive periods ofenergy scarcity, but further suggest that activity time budgets may be selected to reduce mortality risks according to life historypace