Characterizing diurnal roosts of male Little Brown Myotis (Myotis lucifugus) during summer

Abstract

Shelter is one critical aspect of an animal’s habitat, providing refuge from predators and weather, protection for offspring, and aiding in physiological homeostasis. During the day, bats find shelter in roosts—spaces created under tree bark, in tree cavities, or between rocks—after spending the night searching for food. Finding a roost with a microclimate that enables bats to remain in their thermoneutral zone could reduce energetic demands or allow bats to allocate energy to other activities such as reproduction and fighting disease. We aimed to characterize the structural features and microclimate (i.e., temperature) of roosts used by male Little Brown Myotis (Myotis lucifugus) during the summer and determine whether bats select certain characteristics disproportionally to what is available at different spatial scales. During the summers of 2017 and 2018, we radio-tracked 34 male M. lucifugus in Lodgepole Pine-dominated forests. We located at least 1 roost for 20 individuals (average = 2.85 roosts/bat, range = 1 to 6). Although snags were available, most of the roosts were in rock features (86% in rocks, 14% in trees or snags). Male M. lucifugus were more likely to select rock roosts with less canopy closure that were closer to water compared to available roosts on the landscape. They also selected roosts in rock features occurring within larger areas of rock cover that had wider entrances and access to crevices that faced the sky; these roosts also had warmer microclimates relative to other locations available on the landscape. Crevices that allow the bat to bask in the sun and change locations within a roost, minimizing energy needed for active thermoregulation, could be very beneficial for individuals recovering from diseases such as white-nose syndrome. Our work indicates that rock features provide habitat for male M. lucifugus during summer; other studies have shown that bats roost in these features during autumn and winter, further supporting their importance. By protecting these important rock structures, managers can help bats meet their habitat needs throughout the year.