Species-specific patterns of bat activity in an urban landscape

Urbanization is currently considered to have a negative effect on biodiversity, including the abundance and diversity of bat (Chiroptera) communities. However, relatively little attention has been devoted to the urban ecology of bats despite their ubiquity and ecological importance. We conducted a study during 1997-1999 to acoustically monitor species-specific distributions and activity patterns for bats in a highly urbanized landscape. Of 11 896 passes recorded during the study that satisfied our criterion for species classification, 8672 (73%) were identified to species. We identified calls from five species (Eptesicus fuscus, Lasionycteris noctivagans, Lasiurus borealis, Lasiurus cinereus, Pipistrellus subflavus) and the Myotis group. Few landscape variables were significantly related to E., fuscus activity; however, L. borealis and L. noctivagans activity had positive relationships with adjacent industrial/commercial land use and an urban index. We determined mean occurrence at monitoring sites for all identified species, and each species and the Myotis group exhibited positive relationships with the urban index. More species were detected in habitat fragments within urbanized landscapes, and each of these species was detected more frequently in urban areas than in more rural habitat fragments. Correspondence analysis suggested community structure was similar among classes of urbanization, with E. fuscus predominant, although fewer species occurred in rural areas. Urban areas may represent islands of habitat for some bats within larger landscapes dominated by intensive agriculture. Thus, the nature of the relationship between urbanization and bats is probably dependent on context at the macrogeographic scale and local habitat quality within the urban matrix.