INTRODUCTION 



Several species of North American cave-dwelling bats have been adversely affected in 

 recent decades by a variety of human-induced environmental changes to caves, including cave 

 closures, impoundments, and vandalism or other direct human disturbances (see Humphrey 

 1978, Tuttle 1979, LaVal and LaVal 1980, Sheffield et al. 1992). These, and landscape changes 

 such as deforestation (including loss of large trees with basal hollows) and agricultural 

 development, have forced many bat species to abandon traditional sites in search of new roosts 

 and hibernacula As a result of these wide-spread disturbances, some cave-dwelling species in 

 the eastern and Midwestern United States have been listed as threatened or endangered under the 

 U.S. Endangered Species Act. Abandoned mines offer a variety of subterranean microclimates 

 similar to those in natural caves (Tuttle and Stevenson 1978, Tuttle and Taylor 1994) and can 

 provide suitable habitat for roosting and hibernating bats Abandoned mines now serve as 

 principle roosts and hibernacula for many cave-dwelling species (Tuttle and Taylor 1994), and 

 are important for populations occupying marginal habitats (Gates et al. 1984) in areas where 

 there are continued threats to primary natural roosts. It is widely acknowledged that natural cave 

 environments are the most stable and desirable long-term habitats for bats, but abandoned mines 

 may provide a suitable alternative 



Mine reclamation (including closure to restrict human access) is of interest to wildlife 

 managers because reclamation activities can have significant negative impacts on bat populations 

 (see Sheffield et al. 1992, Richter et al. 1993) Therefore, it is important that closure is done in 

 such a way as to minimize disturbance to bats in the mines affected. Because the majority of bat 

 species in Montana use caves and mines, it is especially important to determine the extent and 

 magnitude of mine use by bats in the state, and identify situations where access by humans to 

 abandoned mines can be restricted while maintaining mine attractiveness to bats. 



Increased concern over bat populations nationally, coupled with increased emphasis on 

 the closure of abandoned mines on public lands, has prompted Bureau of Land Management 

 (BLM) biologists in Montana to assess abandoned mines for bat activity prior to mine closure 

 (e.g., Hendricks 1997, Hendricks et al. 1999). A number of abandoned mines in west-central 

 Montana on BLM lands under jurisdiction of the Missoula Field Office are scheduled for closure 

 in the near future Some of these mines may provide habitat critical for hibernation, 

 reproduction, and warm-season roosting by bats, including Townsend's Big-eared Bat 

 (( 'orynorhmus townsendu), a designated Special Status species by the BLM in Montana. 

 Objectives of the surveys reported here include 1) assessing the suitability of several abandoned 

 mine workings as bat habitat, and 2) providing management suggestions that assist in 

 reclamation activities at these workings 



