Responses of insectivorous bats to tree felling in forested wetlands

Forested wetlands provide habitat for a diversity of wildlife and create complex vegetation structure within forests. Current best management practices in New England have limited disturbances in forested wetlands due to concerns for wetland function and water quality. As a result, forested wetlands often have large, mature trees that were formerly rare under natural disturbance regimes. Our goal was to determine whether experimentally felling trees within forested wetlands is an effective management action to improve foraging habitat for insectivorous bats. In the winter of 2019 while the ground was frozen, we felled all trees in an area of approximately 0.1 ha in each of 3 forested wetlands to simulate a natural disturbance, similar to that caused by beaver activity or windthrow. The following spring and summer of 2019 and 2020, we monitored bat activity in the 3 treated forested wetlands as well as 3 untreated forested wetlands. We found that for all species recorded, bat activity was higher in treated wetlands than in untreated wetlands. We also found Lasiurus borealis and Lasionycteris noctivagans had a delayed response to treatments, with higher activity in the second year after treatments. Our findings suggest that managing forested wetlands consistent with historic patterns of forest disturbance and regeneration is beneficial to insectivorous bats. The positive response by bats to tree felling indicates that promoting age-class and structural diversity in forest canopies without flooding or soil disturbance is an appropriate consideration with respect to best management practices in forested wetlands.