Day-roost characteristics of northern bats in mixed mesophytic forest

Management of forests to promote habitat needs of bats requires information on all life requisites of each species. Data on roosting habitat of northern bats (Myotis septentrionalis) is limited for eastern deciduous forests. We radiotracked 13 adult female and 2 adult male northern bats as they used 57 day roosts in mixed mesophytic forest in northeastern Kentucky from 18 May to 5 August 1998. Northern bats used day roosts in 12 species of trees, with sourwood (Oxydendrum arboreum) and shortleaf pine (Pinus echinata) each comprising 29.8% (n = 17/57) of the roost trees, respectively. Colonies, >1 northern bat, were predominantly found in cavities of hardwood snags (44.2%, n = 19/43) or under the bark of shortleaf pine snags (32.6%, n = 14/43). Snags possessing sloughing bark with branches absent were more frequently used as roosting sites by northern bats (52.9%, n = 18/34) than any other stage class of snag. Solitary bats were primarily found roosting in cavities of living hardwood trees (92.9%, n = 13/14). Roost trees of northern bats were not distributed equally among topographic locations, with roosts more frequently situated on upper slopes (45.6%, n = 26) and midslopes (38.6%, n = 22) than on lower slopes (15.8%, n = 9). Mean population size of colonies appeared to decline as summer progressed, with pregnant females using the largest colonies (x̄ = 25.6 ± 10.2 bats), lactating females using intermediate-sized colonies (x̄ = 13.5 ± 2.98 bats), and post-lactating females using the smallest colonies (x̄ = 3.8 ± 1.66 bats). These data suggest that forest management practices that sustain diversity in tree species, tree-size class (3.1-55.8 cm dbh), and snag-condition class (stages 3 and 4) are necessary to provide habitat for northern bats in mixed mesophytic forests.