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, Turtle 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 (Turtle and Stevenson 1978, Turtle 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 (Turtle 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) A number of abandoned mines on BLM land in southwestern Montana 

 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 (Corynorhmus townsendu), a designated Special Status species by the BLM in Montana, 

 identified as a high priority species in 1998 by the Western Bat Working Group, and designated 

 as a species of concern (former C-2 candidate for listing) by the US Fish and Wildlife Service 



Primary objectives of the 1997-1998 abandoned mine inventory on BLM lands in 

 southwestern Montana were to I ) identify specific mine workings used by bats, 2) gather 

 external mine attribute data that might aid in identifying the suitability of unsurveyed workings 

 and predicting broader patterns of mine use, 3) gather internal mine attribute data that will 

 provide baseline environmental information on abandoned mines used by bats, with the 

 expectation that these data will be useful in identifying suitable mine workings, even in the 

 absence of bats, and 4) capture and identify bat species using abandoned mines in the project 

 area 



