SUMMARY 



This report documents the results of a study of bat occurrence in 

 the Pryor Mountains of south central Montana that was initiated 

 in 1989 (Worthington and Ross, 1990) . The 1990 field research 

 was conducted from 15 June to 14 September and resulted in a 

 total capture of 1,101 individuals of 10 species. Bats were 

 captured at ponds, springs, and at the entrance of five caves. 

 Numbers of bats captured were generally greater at the caves. 

 Capture success was considerably lower at water sources, but a 

 greater diversity of species was noted at these sites. While 

 several of the species captured occurred throughout the area, the 

 spotted bat, Euderma maculatum , the pallid bat, Antrozous 

 pallidus , and the silver-haired bat, Lasionycteris noctivagans , 

 were more restricted in distribution. Two specimens of the 

 spotted bat, Euderma maculatum . were captured. These specimens 

 represent the first live spotted bats captured in Montana since 

 1949 (Nicholson, 1950; Hoffmann and Pattie, 1968) . Spotted bats 

 were observed throughout the eastern portion of the study area. 

 Townsend's Big-eared bat, Plecotus townsendii . was previously 

 known only from winter records in the Pryor Mountains; 11 

 individuals were observed in 1990. Seventeen individuals of 

 Antrozous pallidus were captured, bringing to 26 the total number 

 captured in the area since the species was first documented in 

 Montana in 1979 (Shryer and Flath, 1980; Worthington and Ross, 

 1990) . Several of the species of bats found in the Pryor 

 Mountains were captured in numbers significantly different from 

 an expected 1:1 sex ratio. This was especially true at the 

 caves, where males greatly out-numbered females, suggesting that 

 in some species males and females may be differentially utilizing 

 habitat. The generally low temperatures of the caves 

 investigated in this study may preclude their summer use by many 

 female bats, especially pregnant or lactating individuals, which 

 require higher roost temperatures in order to maintain the higher 

 metabolic rate necessary for raising young (Racey, 1982) . Bat 

 activity at the caves, especially Mystery Cave, indicated that 

 these caves provide important summer roosting habitat. 

 Additionally, these caves possess characteristics which may make 

 them important as hibernacula. 



