Summer habitat use of roost trees by the endangered Indiana bat (Myotis sodalis) in the Shawnee National Forest of southern Illinois

Roost trees of Indiana bats (Myotis sodalis) and northern myotis (Myotis septentrionalis) were located using radio telemetry in two locations in southern Illinois. Fifty-three roost trees were located for 31 Indiana bats. Ten adult female northern myotis were tracked to 19 different trees. Indiana bats used seven different tree species and northern myotis used six. Indiana bats used green ash (Fraxinus pennsylvanica ) and pin oaks (Quercus palustris) more than expected and sweetgum (Liquidambar styraciflua) less than expected. Logistic regression was used to create models to predict use between Indiana bats and random trees, northern myotis and random trees, and Indiana bats and northern myotis. Indiana bat roosts differed from available trees by typically being in areas of low roost obstruction (clutter) that were close to intact forests (X2 = 10.284, df = 2, p = 0.006). When compared to random trees, roosts of northern myotis were closer to intact forests (X2 = 10.562, df = 1, p = 0.001). The amount of roost obstruction (clutter) around the roost and decay class of tree were important in distinguishing between the roosts of the two species (X2 = 38.633, df = 2, p < 0.001). Northern myotis roosts were typically more cluttered and not as decayed as those of Indiana bats. Northern myotis also made extensive use of exfoliating bark, cavities and crevices, whereas Indiana bats almost exclusively used exfoliating bark. Indiana bats used a larger area for roosting than did the northern myotis. Additionally, Indiana bats traveled greater distances between roosts than did northern myotis.; I suggest that Indiana bat colonies are ephemeral in a given area because of short-term persistence of their roosting requirements. This makes long-term management of a given site problematic. Land managers may be able to use bat houses to help sustain colonies between natural disturbances that create the necessary roosting habitat.