Little brown bat populations are rebounding at major hibernation sites across Wisconsin, with recent surveys showing recovery after steep declines caused by white-nose syndrome, a fungal disease that arrived in the state in 2014.
The rebound is concentrated in some of the state's historic mines, which serve as critical hibernation grounds. "Just a few of Wisconsin's historic mines are the winter home to a significant percentage of the nation's little brown bats," said Jennifer Redell, a conservation biologist with the Wisconsin Department of Natural Resources. In spring, those bats disperse across thousands of square miles of forests, fields and neighborhoods in the Midwest.
The recovery is significant because of the bats' ecological and economic role. Insectivorous bats consume large numbers of agricultural pests, saving farmers and forest owners billions of dollars annually. Of the eight bat species found in Wisconsin, four are state-threatened, and one, the silver-haired bat, is designated as a special concern because its population is declining.
White-nose syndrome attacks bats' bare skin during hibernation, exhausting their energy reserves and leaving them vulnerable to starvation before their insect diet becomes available in spring. Despite the encouraging signs in little brown bat numbers, other species including tricolored bats and the federally endangered northern long-eared bat remain stressed by the disease and have shown no comparable recovery.