Impacts of Different Forest Tree-Harvest Methods on Diets and Populations of Insectivorous Forest Bats

Abstract

The Hardwood Ecosystem Experiment (HEE) in central Indiana presents an excellent opportunity to study species reactions to different forestry practices: clearcutting, shelter wood cutting, and single tree selections. This project focuses on the differences in the populations and diets of the various insectivorous bat species in the HEE management units. Bats studied were Myotis septentrionalis, Lasiurus borealis, Eptesicus fuscus, Perimyotis subflavus, Myotis sodalis, Myotis lucifugus, and Lasionycteris noctivagans. Since insectivorous bats do not simply eat whatever is available, and I hypothesize that the diets of these bats will not change despite their changing environment and changing populations. To test these ideas, guano was collected between years 2006-2010 and ANABAT calls were recorded between years 2007-2010. I analyzed 440 guano samples, and the invertebrate parts were identified visually to the lowest taxonomic level within a reasonable amount of time; this is most often to family, but always order for the Lepidopterans. The data were compared within each species: before and after treatment, across treatment types, between males and females, and across different months. There was no significant change between bat diets before and after treatments, and each species maintained a specific diet across the years. These results reinforce previous conclusions that bats select among available foods and do not simply eat whatever is available. I also analyzed 5346 call minutes using ANABAT bat detectors. There were significant changes in Myotis sodalis, Lasiurus borealis, and Perimyotis subflavus call minutes. This supports the hypothesis that the diets still remain constant despite the changes in the species populations.