Ecophysiology of Hibernating Eastern Red Bats (Lasiurus Borealis)

Many bats utilize torpor mechanisms to conserve energy during daily rest or seasonal periods of inactivity. Seasonal torpor (hibernation) allows bats to avoid thermoregulatory costs of extreme conditions. Unlike other temperate hibernating bats, eastern red bats (Lasiurus borealis) do not utilize typical hibernacula (i.e. caves). Instead, L. borealis will move into leaf litter during the cold bouts of winter months. Because temperatures fluctuate widely at these winter roost sites, my first goal was to describe the correlation between winter arousals and ambient temperatures (Ta). Additionally, I wanted to track changes in metabolism and body temperature (Tb) during hibernation and arousals at various Ta. Based on these data, I was able to estimate a winter energy budget for this species within a selected temperature profile. Bats were captures during fall of 2003 and 2004 in southwestern Missouri and kept in captivity during the winter seasons in environmental chambers simulating natural conditions. Torpor durations were assessed via temperature-sensitive data-loggers within environmental chambers at 1, 5, 10 and 15°C. Metabolism during torpor (measured as oxygen consumption rates) was assessed at -5, 1, 5, 10 and 15°C. These data were evaluated for differences between gender and Ta. My data suggest that gender has no effect on torpor duration (P = 0.441) and torpor duration was negatively correlated with Ta (P \u3c 0.0005). Gender has no effect on metabolism during Torpor (O2mL/h, P = 0.971; )2mL/h/g, P – 0.191; and O2mL/h/ĝ(0.67), P=0.357) and metabolism during torpor was varied with Ta (P \u3c 0.0005). Additionally, Tb of hibernating bats always remained above Ta and discrepancy between these temperatures was greatest at 1°C. These studies of ecophysiology yield a better understand of this species’ thermal limits and have predictive value when estimating winter energy budgets