TWEL Alexander Silvis Thesis

The response of bats to shelterwood harvest and prescribed fire
 
Alexander Silvis, MS
Advisor: Stanley D. Gehrt
 
 
Declining oak (Quercus spp.) regeneration in eastern forests of North America has become a concern to wildlife biologists and foresters as the loss of oaks as a major overstory component impacts wildlife habitat and timber resources. Consequently, specialized forest treatments utilizing a combination of mechanical thinning and prescribed fire have been developed to favor oak regeneration over that of more shade-tolerant species. Despite increasing and widespread use of these techniques, little is currently known about the effects these activities have on bats (Chiroptera), which are sensitive to changes in forest canopy coverage and clutter. This study quantified bat activity levels in response to changes in canopy clutter resulting from overstory thinning and prescribed burning. Bat activity levels were acoustically monitored using Anabat II bat detectors from May to September in 2006, 2009 and 2010 in two Ohio state forests across 12 treatment areas and 96 plots. Measures of individual tree crowns were made on all plots in 2006 and on a subsample of 30 plots during 2009 and 2010 to estimate changes in canopy volume. Bat activity was negatively correlated with structural volume, and was greater in harvested stands than control stands in all years. Total activity did not change between 2006 and 2009, despite increases in understory structural volume. In contrast, activity levels following prescribed fire were significantly lower, and were not related to decreases in clutter. Activity levels within burned stands were greater than levels within unthinned, unburned control stands. Species specific responses to fire were variable, with big brown bats (Eptesicus fuscus) being more fire tolerant than red bats (Lasiurus borealis) and Myotis bats. The results of this study suggest that while prescribed burning may decrease bat activity within thinned stands, activity will still be greater than in unthinned stands.