Analyzing Bat Activity in Burned Red Pine Stands in Northern Wisconsin

Abstract

Bats in Wisconsin play an important role in their environment as nocturnal insectivores and have been shown to substantially reduce insect populations. At the same time, Wisconsin bats face numerous conservation issues. Problems like white-nose syndrome, windmill strikes, and habitat fragmentation can decimate bat populations. Fire has historically disturbed landscapes in Wisconsin, and many ecosystems have evolved to co-exist with it. For example, red pines self-prune their lower branches to protect against canopy fires. This creates an open mid-story in red pine stands when paired with routine fires that thin out tree and understory cover. The opened-up mid-story has been shown to affect bat community dynamics, locomotion, and foraging styles. Our research project was located at Treehaven, a facility of the University of Wisconsin-Stevens Point, located in northern Wisconsin. We wanted to examine the effects of 1-year burn intervals on bat activity in the red pine stands found on the Treehaven campus compared to control units. We also wanted to examine the efficiency of using stationary detectors vs mobile transects to monitor bat activity. We conducted four mobile transects around three units that are burned every year and three units that are not burned. Stationary detectors were set out for six nights in each of these 2-acre units. We found that the 1-year burn units had a statistically higher bat density than the control units. We were also able to determine that stationary detectors collected more total calls than mobile detectors. We concluded that yearly prescribed fire is beneficial for bat populations.