Long-Term Effects of Forest Harvesting on Habitat Use By Insectivorous Bats

Abstract

The short-term effects of forest harvesting on forest-dwelling bats have received considerable attention. However, knowledge about the long-term effects are also essential to better conserve forest-dwelling bat populations in North America. As vegetation regenerates over time post-harvest, changes created by harvesting (e.g., cutblocks and forest edges) will blur and eventually disappear with natural forest regrowth. Long-term effects of forest harvesting could thus differ from short-term effects on forest-dwelling bat species. To evaluate changes in habitat use by an insectivorous bat community in response to forest harvesting over time, I repeated a study (Grindal and Brigham 1999) conducted near Nelson, British Columbia, Canada. Grindal and Brigham’s principal objective was to evaluate bats’ use of habitats created by or left after clear-cut logging using acoustic detectors. I revisited the same exact locations 20+ years later to determine how bats use the forest regrowth of these habitats. As was done in 1993-94, I assessed bat community activity and insect community composition (bat prey) in three habitats types (i.e. cutblocks, forest edges, unlogged forests) in combination with different habitat features at landscape and local scales. I found that insect community composition within regenerating cutblocks and along forest edges, when compared to adjacent old-growth forests, showed signs of recovery suggesting the movement of the community towards a new equilibrium. I found that the bat community had modified its use of the same disturbed areas since 1993. My results suggest that clutter and openadapted bats mostly foraged and commuted above the canopy of dense and cluttered forest regrowth of regenerating cutblocks and along the remaining vertical forest edges. I also found that clutter-adapted bats flying within vegetation mainly used old-growth forests to forage and commute. By using a different approach than previous studies my research proposes a time and cost-effective way to enhance our knowledge about changes of bat habitat use over time in a dynamic environment.