Predicting niche spaces of expanding Evening Bat (Nycticeius humeralis) populations following white-nose syndrome establishment

Observations of the Evening Bat (Nycticeius humeralis), a species historically distributed abundantly throughout the southeastern United States, are speculated to have increased in the Midwest. One hypothesis for this expansion in geographic distribution is that local extirpations of other bat species resulted in the expanded realized niche spaces for evening bats. In Indiana, such niche spaces may have been created by declines in populations of the Northern Long-eared Bat (Myotis septentrionalis), Indiana Bat (M. sodalis), Little Brown Bat (M. lucifugus), Big Brown Bat (Eptesicus fuscus), and the Tri-colored Bat (Perimyotis subflavus) due to white-nose syndrome (WNS). Our goal was to estimate the occupancy of Evening Bat in Indiana post-WNS establishment relative to the occupancy of other bat species before significant population declines caused by WNS. We expected that indices of occupancy of nearly extirpated species pre-WNS establishment would best predict current Evening Bat observations, and this would elucidate the niche space evening bats are now filling. We hypothesized that Evening Bat populations may be expanding their geographic range due to compensatory community dynamics, and that their realized niche space may be expanding in part due to losses of other bat species from WNS. We constructed multi-season Bayesian occupancy models using informative priors and integrative prior knowledge to test our predictions. We found that evening bats are occupying the niche space they were already occupying pre-WNS establishment. Furthermore, our results indicate that evening bats may be filling the niche space left behind by Myotis spp. (M. sodalis and M. lucifigus). These results can help us understand the dynamics of bat communities in a post-WNS establishment landscape and may also help to inform conservation of imperiled Myotis species.