Bat use of a high-plains urban wildlife refuge

Bats are significant components of mammalian diversity and in many areas ar e of management concern. However, little attention has been given to bats i n urban or prairie landscapes. In 1997 and 1998, we determined species rich ness, relative abundance, roosting habits, and echolocation activity of bat s at Rocky Mountain Arsenal National Wildlife Refuge (RMA), the largest urb an unit in the United States refuge system, located on the high plains near Denver, Colorado. An inventory using mist nets revealed 3 species foraging at this site: big brown bats (Eptesicus fuscus), hoary bats (Lasiurus cine reus), and silver-haired bats (Lasionycteris noctivagans). Big brown bats c omprised 86% of captures (n = 176). This pattern was consistent with contin ental-scale predictions of bat species richness and evenness based on avail ability of potential roosts. Relative abundance based on captures was simil ar to that revealed by echolocation detector Surveys, except that the latte r revealed the likely presence of at least 2 additional species (Myotis spp . and red bats [Lasiurus borealis]). Echolocation activity was significantl y greater (P=0.009) in areas with tree or water habitat edges than in open prairie, suggesting that maintaining such features is important for bats. B ig brown bats commuted greater distances (9.2-18.8 km) from roosts in urban core areas to foraging sites on the refuge than typically reported for thi s species elsewhere, emphasizing the value of the site to these bats. Urban refuges can provide habitat of importance to bat populations, but may be c haracterized by abundant bats that roost in buildings if a variety of other kinds of roosting habitats are unavailable.