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Emerging infectious diseases can have substantial impacts on wildlife health, but also provide an opportunity to understand how populations respond to novel selective pressures. White-nose syndrome (WNS) has decimated some populations of bats in eastern North America, but impacts vary among species. We counted bats in 11 hibernacula in Ontario, Canada, before and after WNS arrived, and compared the relative abundance of 5 bat species captured pre-WNS (1966–1968 and 2007–2009) and post-WNS (2017–2019) during swarming at one of these hibernacula. Counts of hibernating bats declined by 87%–100% after WNS arrived. However, we observed a recent, gradual increase in bat counts in the two largest, monitored hibernacula. During swarming, little brown bat (Myotis lucifugus (Le Conte, 1831)) was the most frequently captured bat in all sampling periods. Capture frequency of northern long-eared bat (Myotis septentrionalis (Trouessart, 1897)) declined precipitously after WNS arrived, while eastern small-footed bat (Myotis leibii (Audubon and Bachman, 1842) represented a higher proportion of bat captures in 2017–2019 compared to other sampling periods. Our data suggest potential adaptation of some bat populations to WNS, but also highlight the importance of protecting bats and their habitat during the active season to facilitate population recovery. [ABSTRACT FROM AUTHOR]

Wildlife are exposed to neurotoxic mercury at locations distant from anthropogenic emission sources because of long-range atmospheric transport of this metal. In this study, mercury bioaccumulation in insectivorous bat species (Mammalia: Chiroptera) was investigated on a broad geographic scale in Canada. Fur was analyzed (n = 1178) for total mercury from 43 locations spanning 20° latitude and 77° longitude. Total mercury and methylmercury concentrations in fur were positively correlated with concentrations in internal tissues (brain, liver, kidney) for a small subset (n = 21) of little brown bats ( Myotis lucifugus ) and big brown bats ( Eptesicus fuscus ), validating the use of fur to indicate internal mercury exposure. Brain methylmercury concentrations were approximately 10% of total mercury concentrations in fur. Three bat species were mainly collected (little brown bats, big brown bats, and northern long-eared bats [ M. septentrionalis ]), with little brown bats having lower total mercury concentrations in their fur than the other two species at sites where both species were sampled. On average, juvenile bats had lower total mercury concentrations than adults but no differences were found between males and females of a species. Combining our dataset with previously published data for eastern Canada, median total mercury concentrations in fur of little brown bats ranged from 0.88–12.78 μg/g among 11 provinces and territories. Highest concentrations were found in eastern Canada where bats are most endangered from introduced disease. Model estimates of atmospheric mercury deposition indicated that eastern Canada was exposed to greater mercury deposition than central and western sites. Further, mean total mercury concentrations in fur of adult little brown bats were positively correlated with site-specific estimates of atmospheric mercury deposition. This study provides the largest geographic coverage of mercury measurements in bats to date and indicates that atmospheric mercury deposition is important in determining spatial patterns of mercury accumulation in a mammalian species. [ABSTRACT FROM AUTHOR]