Interspecific variation in evaporative water loss and temperature response, but not metabolic rate, among hibernating bats

Hibernation is widespread among mammals in a variety of environmental contexts. However, few experimental studies consider interspecific comparisons, and for many unstudied (or understudied) species we must assume the underlying physiology of hibernation is comparable to the relatively few species that have been studied in detail. Studies of interspecific variation provide insight into general patterns of hibernation strategies. We studied 13 species of free-living bats, including populations spread over thousands of kilometers and diverse habitats. We measured torpid metabolic rate and evaporative water loss (two key parameters for understanding hibernation energetics) across a range of temperatures. Response to ambient temperature varied among species, but all species achieved similar minimum torpid metabolic rate. Conversely,  evaporative water loss varied among species and our results suggest two general hibernation strategies in North American bats, representing high and low evaporative water loss groups. Notably, species that have suffered population declines due to white-nose syndrome fall in the high evaporative water loss group and less affected species in the low evaporative water loss group. Documenting general patterns of physiological diversity, and associated ecological implications, contributes to broader understanding of biodiversity, and may help predict which species are at greater risk of environmental and anthropogenic stressors.