All adult males in this study exhibited small testes size, and 

 were considered to be non-scrotal. Adult females that possessed 

 mammary glands which were swollen or from which milk could be 

 exuded were considered lactating. Adult females that possessed 

 mammary glands around which hair was lacking but which were not 

 swollen were considered post-lactating, and females that 

 possessed mammary glands around which hair was present were 

 considered non-lactating. Bats were classified as adults or 

 juveniles based upon the degree of epiphyseal-diaphyseal fusion 

 of wing bones (Anthony, 1988) . A bat was considered to be a 

 juvenile if the epiphyseal-diaphyseal fusion of the bat's back- 

 lighted wing appeared to be incomplete. Body mass was determined 

 by placing bats in a small plastic bag and weighing them using a 

 50 gm Pesola scale. Forearm length was measured using vernier 

 calipers. Most bats were marked using color and number coded 

 split-plastic wingbands (Barclay and Bell, 1988) to facilitate 

 identification upon recapture. 



Caves at which bats were captured were also entered in order to 

 record temperature and humidity and to describe structural 

 characteristics. Additionally, several abandoned uranium mines 

 along the Red Pryor Mountain Road were entered and temperature 

 recorded. 



Special efforts were placed on locating Euderma maculatum and 

 Plecotus townsendii . Trapping continued at three sites where 

 capture success was otherwise low in an attempt to capture these 

 species. In addition to trapping efforts, aural monitoring was 

 conducted in an attempt to locate Euderma maculatum . This is the 

 only species of bat in the study area that possesses an 

 echolocation call audible to the unaided ear (sensu Fenton et 

 al., 1984) and was easily identifiable. Monitoring for Euderma 

 maculatum was conducted primarily within the Bighorn Canyon NRA. 



RESULTS 



Bats were captured at five caves and four water sources. These 

 sites were investigated on 50 nights between 22 June and 11 

 September 1990. Additionally, nine mines and the five caves were 

 entered and temperature and humidity recorded. A total of 1,101 

 bats were captured representing ten species (Table 3). Of 1,079 

 bats marked (273 in 1989, 806 in 1990), 86 individual bats were 

 recaptured, representing 98 total recaptures. Of the total, 38 

 (39%) recaptures represent bats marked in 1989, the remaining 60 

 (61%) having been marked during 1990. All of the recaptures 

 occurred at one of four caves: Mystery, Little Ice, Royce, and 

 Four-eared. Only one recapture represented a bat that had moved 

 between caves, a male long-eared myotis, Myotis evotis, that was 

 captured at Little Ice Cave in 1989 and recaptured twice in 1990 

 at Royce Cave. 



10 



