Tree roosts of northern long‐eared bats following white‐nose syndrome

Abstract

ABSTRACTSpring emergence and summer maternity seasons are critical to long‐term survival of cave‐hibernating bats inhabiting geographic regions affected by white‐nose syndrome (WNS). White‐nose syndrome reached cave‐hibernating populations of bats in Mammoth Cave National Park (MCNP), Kentucky, USA, in 2013, with significant declines in several species of bats that hibernate in MCNP during winter 2014–2015, including the northern long‐eared bat (Myotis septentrionalis). To assess behavior and roost selection of individuals surviving to spring emergence and the summer maternity season, we radio‐tracked 26 northern long‐eared bats captured at various locations with differing habitat conditions in MCNP during 2015 and 2016. We tracked bats daily to identify roosting sites and patterns in use of roosts, describe habitat conditions associated with roosting sites, and quantify variation in size of colonies occupying roost trees. The average number of bats emerging from roost trees (3.58 ± 0.57 [SE]) was low compared with estimates for the species in studies completed pre‐WNS. Adult female bats selected trees within 6 roost areas with no overlap in use of roost areas between non‐reproductive females in spring and pregnant and lactating females in summer. Variation in roost tree and surrounding forest characteristics occurred across sex and reproductive condition classes, with males and pregnant and lactating females roosting at higher landscape positions than non‐reproductive females. Comparisons of roosting habitat models demonstrated the torpor model (decay class, stem diameter, canopy cover) to be parsimonious, regardless of sex and reproductive condition class, suggesting importance for choosing roost trees that facilitate use of daytime torpor. Such a strategy would promote energy savings and be consistent with behaviors anticipated for bats vulnerable to WNS effects during winter hibernation because these bats are potentially compromised in health and physiologic condition upon emergence from hibernation in spring. We encourage land managers responsible for roost trees of northern long‐eared bats to consider seasonal and landscape‐level variation in roosting habitat needs of these bats. © 2017 The Wildlife Society.