Diurnal roost selection of northern long-eared bats on the southern edge of their range

Abstract

Mortality from white-nose syndrome has made management and recovery of the northern long-eared bat (Myotis septentrionalis) a priority. Ensuring availability of diurnal summer roosts, where gestation and rearing of young occurs, is a critical component of successful recovery. However, observed variation in roost selection across the species’ range makes extrapolating data across physiographic regions and habitat types difficult, and limited information exists on roost selection at the southern range extent of the species. Therefore, we examined M. septentrionalis diurnal roost selection toward the southern range extent in northern Georgia, USA. We identified characteristics of desirable roosts for all individuals and for reproductive females by comparing roosts to surrounding vegetation and topographic characteristics at the plot, home range (67 ha), and landscape (17.2 km2) scales. From May to July 2014–2017, we radio tagged 12 female and 4 male M. septentrionalis and located 37 roosts. Bats roosted in cavities, loose bark, and hollow boles of 16 tree species. Over half of roosts (53%) were located below the canopy and in trees with larger diameters than surrounding trees. Bats disproportionately roosted in snags, with relative probability of selecting a snag roost increasing with snag density at the plot scale. On low gradient slopes, roosts occurred more frequently on west-facing aspects but as slope increased bats showed no aspect preference. Results indicate individuals in our study area are indifferent to or actively avoid roosts with high solar exposure. Our results support previous research that management efforts should focus on creating and retaining snags across the landscape and highlight the need for management to consider regional variation in habitat use.