Roost and Forage Site Fidelity of Western Small-Footed Myotis (Myotis ciliolabrum) in an Oregon Desert Canyon

Abstract

We describe the roosting and foraging behavior patterns of western small-footed myotis (Myotis ciliolabrum) observed during a vertebrate inventory of the John Day Fossil Beds National Monument in north central Oregon. We used radiotelemetry to track 9 adult females, including 3 lactating and 6 postlactating bats, during July-September 2003. We found that these bats showed considerable fidelity to a common foraging area at the confluence of the John Day River and a tributary creek along which bats commuted and roosted. Individual bats did not roost together, but each showed high fidelity to local clusters of rock outcrops in small side canyons along the tributary. Roosts were not found in large, exposed cliff faces, despite the availability of such features. Rather, radio-tagged bats roosted in smaller outcrops that averaged 4.5 m in height. Bats commuted up to 12 km from roosts in the tributary canyon to the common foraging site at the river confluence and remained on the wing to forage for up to 4 h before returning to day roosts. No radio-tagged bats were observed using night roosts, even after pups were weaned. Our study provides a description of roosting, commuting, and foraging activity, as well as habitat use, of western small-footed myotis. This information provides a nuanced perspective on the ecology of canyon-dwelling bats in the region. Such perspective could be useful for conservation and habitat management.