INTRODUCTION 



Exploration and exploitation of uranium deposits on the southern exposures of the Pryor 

 Mountains in Carbon County of south-central Montana, quickly developed in the 1950's and 

 declined about as rapidly in the 1960's. Although the majority of workings are little more than 

 prospect pits or scrapes and most underground workings extend only a few yards, a few 

 abandoned mine sites include workings with more extensive underground passageway. 

 Reclamation of abandoned mine workings in 1989 included postmg warning signs at portals and 

 construction of fencing around open pits and shafts at sites with the most significant underground 

 workings. Thus, several underground workings remain accessible both to bats and humans 

 despite reclamation efforts. 



Perhaps because of the abundance of natural caves in the Pryor Mountains (Campbell 1978), the 

 area is occupied by a relatively large diversity of bat species, ten species documented so far 

 (Worthington 1991 ). Six bat species that could occupy abandoned mines in the Pryor Mountains 

 (Western Small-footed Myotis [Myotis ciliolabnaii]. Western Long-eared Myotis [M. evotis]. 

 Little Brown Myotis [A/, luclfiigiis]. Long-legged Myotis [M. volans]. Big Brown Bat [Eptesiciis 

 fuscus], Townsend's Big-eared Bat [Coiynorhiints townsendii]) are known from Pryor Mountain 

 caves (Worthington 1991 ). Of these six species, four (excepting Little Brown Myotis and Big 

 Brown Bat) are considered species of special concern by the U. S. Fish and Wildlife Service 

 (Hai-vey et al. 1999). 



There have been few efforts to systematically document bat use of caves in the Pryor Mountains, 

 with the notable exception of Worthington (1991 ). Documenting bat use of abandoned 

 underground mines in the Pryor Mountains has received less attention, even though mines have 

 supplemented or replaced caves as key year-round bat habitat in many regions of the United 

 States (Tuttle and Taylor 1994). The primary objectives of our field work in summer 2001 were 

 to: 1 ) assess the use by bats of several mine sites with underground workings still accessible to 

 them, and 2) offer suggestions for protection of significant bat roosting habitat from human 

 disturbance, should such habitat be identified. 



STUDY AREA AND METHODS 



The Pryor Mountains of Carbon County, Montana lie near the Wyoming border to the west of 

 the Big Horn River, and are separated from the Big Horn Mountains by the impressive gorge of 

 Big Horn Canyon. The Pryor Mountains are a series of asymmetric anticlines forming four 

 major uplifted mountain blocks (Campbell 1978), one of which is the Big Pryor Mountain block 

 where a series of abandoned uranium mines are located. Nearly all of the surface rock of the 

 Pryor Mountains is uplifted Madison Group limestone, which harbors numerous solution caves 

 in the upper portions of the Mission Canyon Formation. Base elevation on the southern slopes of 

 Big Pryor Mountain in Montana is 4600', reaching 8786' at the summit. 



A series of abandoned uranium mines are found between Gypsum Creek to the west and 

 Crooked Creek to the east. They range in elevation from 5380-7800' and are located on the 

 south-facing slope of a spur ridge leading to Red Pryor Mountain on the summit ridge of Big 

 Pryor Mountain. This cluster of abandoned mines was the focus of reclamation activity in 1989 



