Abstract
Few studies have described winter microclimate selection by bats in the southern United States. This is of particular importance as the cold-adapted fungus, Pseudogymnoascus destructans, which causes the fatal bat disease white-nose syndrome (WNS), continues to spread into southern United States. To better understand the suitability of winter bat habitats for the growth of P. destructans in this region, we collected roost temperature and vapor pressure deficit from 97 hibernacula in six ecoregions in Texas during winter 2016-17 and 2017-18. We also measured skin temperature of Rafinesque's big-eared bats (Corynorhinus townsendii), Townsend's big-eared bats (C. townsendii), big-brown bats (Eptesicus fuscus), southeastern myotis (Myotis austroriparius), cave myotis (M. velifer), tri-colored bats (Perimyotis subflavus), and Mexican free-tailed bats (Tadarida brasiliensis) during hibernation to study their use of torpor in these habitats. We found that temperatures within hibernacula were strongly correlated with external air temperatures and were often within the optimal range of temperatures for P. destructans growth. Hibernacula and skin temperatures differed among species, with Rafinesque's big-eared bats, southeastern myotis, and Mexican free-tailed bats occupying warmer microclimates and having higher torpid skin temperatures. For species that were broadly distributed throughout Texas, hibernacula and skin temperatures differed within species by ecoregion; Tri-colored bats and cave myotis in colder, northern regions occupied colder microclimates within hibernacula and exhibited colder skin temperatures, than individuals of the same species in warmer, southern regions. These data illustrate the variability in microclimates used as hibernacula by bats in Texas and suggest similar variation in susceptibility to WNS in the state. Thus, monitoring microclimates at winter roosts may help predict where WNS may develop, and where management efforts would be most effective.
Highlights
The choice of overwintering habitat has numerous impacts on mammalian hibernators
To improve our overall understanding of the suitability of bat habitats for P. destructans— and potentially white-nose syndrome (WNS)—in Texas, and to better inform management practices, we described the microclimates used by seven bat species as hibernacula across the state
We found that bats hibernate under diverse conditions across Texas, and observed broad differences in selected microclimates and torpid skin temperatures among species
Summary
The choice of overwintering habitat has numerous impacts on mammalian hibernators. Suitable hibernacula must provide an appropriate thermal environment. Defining appropriate thermal habitats has been the focus of research for decades, as the temperatures inside. Winter habitats of Texas bats (CFDA# 15.611) as administered by Texas Parks and Wildlife Department, https://tpwd.texas.gov/ and the U.S Fish and Wildlife Service (CFDA# 15.657), https://www.fws.gov/ (MLM, BLP). Additional funding support was provided by the Fightwns ‘Micro Grants for Microbats’, https:// www.fightwns.org/, Texas Ecolab research grants, https://texasecolab.org/, and National Speleological Society WNS Rapid Response Grant, https://caves. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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