Baseline data on bat distribution and habitat use is essential for bat conservation. Little information exists on bats in the southern boreal forests of the Midwest. We measured summer bat habitat use and foraging activity at aquatic, linear corridor, and interior forest sites with bat detectors in deciduous, mixed-wood, and coniferous forests in northeastern Minnesota. We used three common acoustic bat activity indices to quantify acoustic bat data and we compared the results of each index. We further examined the indices to determine how differences among bat activity indices influence statistical inferences of bat activity. We measured the effects of relative insect abundance and degree of vegetation density on bat activity. We recorded all seven resident bat species across the study area. We recorded 7,666 identifiable bat calls during 1,440 detector hours in 2009. In 2010 we recorded 8,554 bat calls during 930 detector hours. Bat activity, dominated by Myotis species (Myotis lucifugus and M. septentrionalis), Lasiurus borealis, and Lasionycteris noctivagans, was concentrated at aquatic and linear corridor microsites, regardless of forest cover type. However, bats foraged at similar rates in each microsite type. Bat activity and foraging activity occurred earlier at interior forest sites relative to aquatic and linear corridor sites, suggesting that interior forest is also important habitat for bats as they leave day roosts to forage. Bat activity indices had clear biases, but resulted in similar statistical inferences of habitat use of northeastern Minnesota bat species.
University of Minnesota M.S. thesis. February 2011. Major: Integrated Biosciences. Advisor: Dr. Ronald A. Moen, Ph.D. 1 computer file (PDF); vii, 43 pages, appendix p. 43.
Abel, Rebecca Laura.
Measuring habitat use by bats in northeastern Minnesota using acoustic methods..
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