Meeting Abstract
Energetics of mammalian hibernation can be considered in terms of three phases: positive energy balance before winter; negative energy balance during winter; and spring recovery when positive energy balance is restored. Hibernation itself is comprised of long torpor bouts (periods of low body temperature (Tb) and metabolic rate) interrupted by brief arousals to normal Tb. The function of arousals is not fully understood but they are obligatory for mammals and account for most winter energy expenditure. Most data on hibernation come from rodents but insect-eating bats have potential for studying tradeoffs affecting all three phases of hibernation. Our group has been studying little brown bats (Myotis lucifugus) to test the hypothesis that similar tradeoffs influence all three phases of hibernation for rodents and bats despite dramatic differences in hibernation ecology and behavior. Data collected using temperature telemetry, infrared video, passive transponders (PIT tags) and plasma metabolite analyses suggest that individual and group characteristics (sex differences in reproductive timing, individual personality), and environmental factors (weather, winter duration) influence hibernation energetics and phenology. Our measurements of cortisol in claws of bats that survive the devastating fungal disease white-nose syndrome (WNS) highlight the trade-off between winter energy expenditure and summer reproduction, and suggest that effects of winter stressors carry over from one season to the next. This work has implications for understanding the evolution of hibernation, ecology of temperate-zone bats, and potential value of management strategies proposed for WNS.
