Managed forests provide roosting opportunities for Indiana bats in south-central Indiana

Abstract

There is an intense interest in the effects of timber harvest on forest-dwelling bats due to the potential for timber harvest to reduce available habitat. Knowledge of these effects would be especially significant for the conservation of threatened and endangered bat species, many of which are forest obligates. We conducted a study to determine how endangered Indiana bats (Myotis sodalis) select summer roosts within a managed midwestern forest. In the summers of 2012–2015, we tracked 4 male and 11 female Indiana bats to 49 roosts (nmale = 24, nfemale = 25) in south-central Indiana, USA. We collected roost-, plot-, and stand-scale data on roosts and associated available trees, randomly located throughout the same landscape. We generated 10 matched pairs conditional logistic regression models based on a priori hypotheses on roost selection and ranked them using Akaike’s Information Criteria. Plausible models explaining female roost selection included those describing typical Indiana bat maternity roosts (tall and solar-exposed roosts) and typical tree-cavity bat roosts (tall, solar-exposed roosts close to water and surrounded by snags). Females selected roosts under exfoliating bark on large (averaging 17 ± 2 m in height and 34.8 ± 3.0 cm in diameter) standing dead trees (snags; 72% of roosts) and in bat boxes (20% of roosts) with high solar exposure (28.0 ± 6.0% canopy closure above roosts). For males, the model describing predator avoidance (tall roosts with many available snags and live trees) was the most plausible explanation of roost selection. Males selected for roosts under exfoliating bark on tall trees (23 ± 2 m; 71% snags, 25% live trees) surrounded by snags (4.5 ± 0.7 snags/0.1 ha plot) and live trees (30.4 ± 2.7 live trees/0.1 ha plot). Roost selection models including distance to timber harvest openings were not plausible. However, females roosted in or ≤10 m from harvest openings and first-stage shelterwood cuts more than expected (15 of 25 roosts) based on their availability on the landscape. Males roosted in harvest openings as expected (3 of 24 roosts). Our results demonstrate that a managed midwestern forest provides an array of roosts for Indiana bats and that Indiana bats do not actively avoid roosting near harvest openings in this forest. This suggests that Indiana bats may be able to subsist in managed forests in south-central Indiana, provided adequate maternity roost habitat (i.e., large standing dead trees with high solar exposures) is available.