Roost elevation and ambient temperature best predict use of summer heterothermy in eastern red bats

Abstract

Temperate bat species cope with environmental temperatures outside their thermoneutral zone through physiological responses, habitat selection, and social roosting. While there have been several studies examining these factors in bat species that form maternity colonies in tree cavities, underneath bark, or in manmade structures, such studies rarely focus on bats that roost solitarily in tree foliage. To better understand the thermal environment of a foliage‐roosting bat and how they respond to thermal stimuli, we used temperature‐sensitive radio‐telemetry and environmental dataloggers to study the eastern red bat (Lasiurus borealis) in southeast Ohio. We collected skin temperatures from eight male and nine reproductive female bats in combination with microclimate data from 25 bat roosts and 15 random trees. We found that elevation, minimum ambient temperature, and maximum ambient temperature best predicted bat skin temperatures, while sex had little effect. We also found that trees located at higher elevations had warmer canopy microclimates than those at lower elevations, but temperatures did not differ between roost and random trees. These results show that solitary, foliage‐roosting species use torpor extensively in response to cool temperatures during summer. These results have conservation implications, indicating that areas on the landscape with warmer conditions are important for reducing the cost of maintaining euthermic body temperatures. In southeastern Ohio, this includes upland forests, but our data suggest that temperatures at slope positions, and not the elevation itself, are the important habitat feature for eastern red bats.