Indiana bat roosting behavior differs between urban and rural landscapes

Abstract

Urbanization may negatively affect forest obligate bat species. We compared the roosting behavior of federally endangered Indiana bats (Myotis sodalis) in a fragmented site, located on the leading edge of a developing urban area (Indianapolis, IN), with a site of relatively contiguous forest cover in Indiana, USA, during the summers of 2013–2015. Bats in both sites used large standing dead trees and bat boxes with low levels of overhead canopy closure (fragmented site: 26.1 ± 11.0%, contiguous site: 20.1 ± 7.3%) as primary roosts (large groups of bats resident over many days). Between the 2 sites, secondary roosts (individual bats or small groups resident for only a few days) differed in canopy closure at the roost-scale (fragmented site: 66.9 ± 5.1%, contiguous site: 37.1 ± 9.3%); secondary roosts in the contiguous site resembled solar-exposed primary roosts. Bats in the fragmented site switched roosts less often (1.7 ± 0.5 switching events/bat, 5.8 ± 1.7 days of use/roosts) and traveled shorter distances between roosts (702 ± 211 m) than bats in the contiguous site (2.3 ± 0.6 switching events/bat, 2.4 ± 0.4 days of use/roosts; 1216 ± 337 m between roosts). This suggests that the fragmented site may have had low densities of available roosts, which may help explain the heavy use of bat boxes by bats in the fragmented site. These data suggest that urban populations of Indiana bats behave differently than those in rural areas, which managers should consider while managing for this species.