Summer ecology of the Indiana bat (Myotis sodalis) in an agricultural landscape
Andrew B. Kniowski, MS
Advisor: Stan Gehrt
The majority of the summer range of the Indiana bat (Myotis sodalis) is within agricultural areas, yet despite known negative effects of agriculture, few studies have examined the ecology of the Indiana bat within a highly agricultural landscape. To evaluate the effects of agriculture on Indiana bats I asked the following questions: 1) Do Indiana bats selectively use habitat within an agriculturally-dominated landscape? 2) Do Indiana bats select habitat differently at different spatial scales within an agricultural landscape? and 3) Do Indiana bats select and use habitat within an agricultural landscape differently than other areas of their range?
From a study area along Big Darby Creek in Pickaway Co. Ohio USA, I captured 60 Indiana bats (including five recaptured bats) July–September 2008, April–September 2009, and April–September 2010. I calculated home ranges of 32 individuals that had an average area of 210.5 ha } 130.6 SD. I used distance based analysis to evaluate habitat selection within the home range, and at 1200 m and 4000 m spatial scales. At each scale, bats selected areas closer to forest and open water and farther from cropland than was expected by chance. The bats heavily used the wooded creek corridor, but also utilized wooded patches in upland areas. I tracked 51 bats to 56 roost trees 474 times. The bats used roost trees in a variety of locations and across a broad area. Most roost trees were located within the wooded creek corridor, but seven were more than 1 km from open water. I evaluated the location of roost trees within the landscape at 1200 m and 4000 m spatial scales. Roost trees were not located randomly at either spatial scale. The only significant factor in both cases was the distance to open water. There was also was a significant difference in physical characteristics of used and available roost trees (A = 0.257, P = 0.025) and primary and secondary roost trees (A = 0.032, P = 0.013). Widely scattered roosts suggest Indiana bat colonies use a broad area within the context of an agricultural landscape. The selection of habitats in a highly agricultural landscape appears similar to other landscapes and the selection is consistent over a broad range of spatial scales. Preserving forested areas with ample supplies of snags within agricultural landscapes, including smaller patches and especially along waterways, should be a conservation priority for the Indiana bat.