Summer cave use by tricolored bats declined in response to white-nose syndrome despite persistence in winter hibernacula in the southeastern United States

Abstract

Abstract Several bat species have experienced rapid population declines in the northern United States and Canada in response to the white-nose syndrome (WNS) epizootic. The pathogen has since spread across the United States, including the Southeast, where relatively warm temperatures may change host–pathogen interactions. In the cave-rich Tennessee–Alabama–Georgia (TAG) region, we examined the impacts of WNS and forest cover on the Tricolored Bat (Perimyotis subflavus) metapopulation using a long-term data set of 832 cave surveys conducted in summer and winter from 2004 to 2022. Most bat colonies were small (<30 individuals), and bats were more likely to be present and abundant in caves surrounded by high percent forest cover, reiterating the importance of forest management for bat conservation. When comparing the years before and after the pathogen arrived in 2010 to 2012, bat presence and abundance during winter hibernation did not change. This stability contrasts with significant declines in other studies, suggesting that Tricolored Bat populations respond differently to WNS in small colonies in the TAG region. Fewer tricolored bats used caves in the summer than during hibernation, but across all years, we observed 1,021 tricolored bats in 121 caves during summer surveys. Unlike stable winter trends, bat presence and abundance declined in the post-WNS period in summer, when cave use is optional. This first broad geographical analysis of summer cave use highlights a potentially important change in bat behavior. Disease surveillance and conservation efforts that target caves with relatively small Tricolored Bat colonies in winter and/or summer may be important for regional population persistence of this threatened species.