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

Abstract

Spring 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.

Systematic Review of the Roost-Site Characteristics of North American Forest Bats: Implications for Conservation

“…Preferable roost trees tend to be near water [106,176] and/or corridors [86,177], thus reducing the energetic demands of foraging. While males and nonreproductive females may be less restricted by their biological needs, pregnant and lactating females tend to select roosts with closer proximity to foraging resources [140]. Landscape attributes have significant predictive power when evaluating roost-site suitability [177], and including more data regarding the landscape in which roosts are situated may have provided additional context for the results of our study.…”

Roosting Behavior of Northern Long-Eared Bats (Myotis septentrionalis) in an Urban-Adjacent Forest Fragment

“…Northern long-eared bats (Myotis septentrionalis) are one of the forest-dependent species currently experiencing population declines in North America due to habitat loss and WNS [51][52][53]. Northern long-eared bats are considered endangered in the state of Indiana and are currently under consideration for classification as federally endangered in the United States [54].…”

“…The presence of a northern long-eared bat population in an exurban nature preserve warrants investigation, especially since one individual was a reproductive female that we tracked to a roost in a large, solar-exposed snag just outside of the largest nearby forest patch, a roost type more characteristic of Indiana bats in the Midwest United States [57,58]. Many studies have speculated that northern long-eared bats select more solar-exposed roosts when faced with increased energetic demands, such as those associated with reproduction [53,59,60]. However, few studies have directly studied northern long-eared bat body temperature and torpor use, especially in relation to the characteristics of roost trees [61,62].…”