Impact of the Presence of Pseudogymnoascus Destructans on Activity of Montana’s Bat Species

Abstract

In 2019 the pathogenic fungus Pseudogymnoascus destructans (Pd) which causes the disease White‐Nose Syndrome (WNS) was first detected in Montana. In 2020 Montana began surveys following guidance from the North American Bat Monitoring Program (NABat) to determine the status and inform management of bat species within the state. This effort uses acoustic recording units to record echolocation calls of bats at up to four sites within 10 by 10 km cells. Over the past four years, partners have surveyed 1476 sites within 122 cells. Over 3 million calls have been recorded representing 13 of Montana’s 15 species. Making inference about the trend of WNS impacted species using counts of recorded calls is difficult as calls may represent one or many bats. The large amount of data increases reliance on identifications suggested by the classification software but similarity between calls made by different species can reduce confidence in the suggested species. To address these challenges and minimize risk of misclassification we used a thresholding approach based on characteristic frequency to identify calls made by WNS susceptible species. These calls were then used as a response variable in a Bayesian, hierarchical, spatially misaligned regression model that included environmental and geographics factors as covariates, and allowed for estimation of the impact of fungus presence on the log‐mean bat relative activity. Our results indicate that fewer calls from WNS species are recorded in areas where Pd has been detected, confirming that despite differences in overwintering ecology of bats within the West, declines are likely.