Species‐specific responses to white‐nose syndrome in the Great Lakes region

Abstract

White‐nose syndrome is a fungal disease that is threatening bat populations across North America. The disease primarily affects cave‐hibernating bats by depleting fat reserves during hibernation and causing a range of other physiological consequences when immune responses are suppressed. Since it was first detected in 2006, the disease has killed millions of bats and is responsible for extensive local extinctions. To better understand the effects of white‐nose syndrome on various bat species, we analyzed summer acoustic survey data collected from 2016 to 2020 at nine US National Parks within the Great Lakes region. We examined the effect that white‐nose syndrome, time of the year relative to pup volancy, habitat type, and regional variation (i.e., park) have on the acoustic abundance (i.e., mean call abundance) of six bat species. As expected, little brown bat (Myotis lucifugus) and northern long‐eared bat (Myotis septentrionalis), both hibernating species, experienced a significant decline in acoustic abundance following white‐nose syndrome detection. We observed a significant increase in acoustic abundance as white‐nose syndrome progressed for hoary bats (Lasiurus cinereus) and silver‐haired bats (Lasionycteris noctivagans), both migratory species that are not impacted by the disease. Contrary to our predictions, we observed an increase in big brown bat (Eptesicus fuscus; hibernating) acoustic abundance and a decrease in eastern red bat (Lasiurus borealis; migratory) acoustic abundance following the detection of white‐nose syndrome. We did not observe any significant changes after the onset of white‐nose syndrome in the seasonal patterns of acoustic activity related to pup volancy, suggesting that production or recruitment of young may not be affected by the disease. Our results suggest that white‐nose syndrome is affecting the acoustic abundance of certain species; however, these changes may not be a result of reduced reproductive success caused by the disease. In addition, species population dynamics may be indirectly affected by white‐nose syndrome as a result of reduced competition or a foraging niche release. We also found that for parks located at higher latitudes, little brown bat and northern long‐eared bat were more likely to experience greater declines in acoustic abundance as a result of white‐nose syndrome. Our work provides insight into species‐specific responses to white‐nose syndrome at a regional scale and examines factors that may facilitate resistance or resiliency to the disease.