The 2003 study of bat roosts in the John Day Fossil Beds National Monument supplemented ongoing vertebrate inventory information and developed significant new information on the roosting and foraging ecology of the pallid bat, western small-footed myotis, and the spotted bat in the lower John Day River valley. The University of Idaho Department of Fish and Wildlife Resources conducted the study under a cooperative agreement with the Pacific Northwest Cooperative Ecosystem Studies Unit. The primary goal of the study was to determine the location, size, and physical characteristics of maternity colonies for four bat species of concern in and adjacent to the monument. The four target species were the pallid bat, Townsend's big-eared bat, western small-footed myotis, and the silver-haired bat. Each of these species are listed by state and federal agencies as species of concern. Additional goals included the collection of information on the foraging behavior of the western small-footed myotis and the spotted bat.