ABSTRACT 



Surveys of bat activity in the Little Rocky Mountains of Phillips County were conducted 

 in 1997 and 1998 to supplement survey data gathered in 1996. Focus of the 1997-1998 field 

 work was bat use of Azure Cave, the largest bat hibernaculum in the state and one of the largest 

 in the Pacific Northwest and Northern Rocky Mountains regions. Three rock-shelter caves were 

 also evaluated for bat use. Three hibernation counts in Azure Cave (April 1997 and 1998, 

 November 1998), and two trapping sessions at the mouth of Azure Cave (October 1997, 

 September 1998), were conducted during the study. 



Counts of hibernating bats in Azure Cave indicated a significant increase since 1978, the 

 first count available for the cave, and the only complete count for the hibernation period. In 

 April 1978, maximum count was 528. Mean counts in April 1997 and 1998 were 1246 and 1120, 

 respectively. Mean count in November 1998 was 1604. Four species of bats were documented 

 in Azure Cave in 1997-1998: Townsend's Big-eared Bat (Corynorhinus townsendii), Big Brown 

 Bat (Eptesicus fuscus), Little Brown Myotis (Myotis lucifugus), Long-legged Myotis (Myotis 

 volans). Most use continues to be by species of Myotis. 



Two nights of netting in October 1997 at the mouth of Azure Cave resulted in capture of 

 15 bats of three species: Townsend's Big-eared Bat (1), Big Brown Bat (13), Little Brown Myotis 

 (1). Two of the Big Brown Bats were recaptured males marked at the cave in October 1996. 

 Two nights of netting at the cave in September 1998 resulted in capture of 150 bats of six 

 species: Townsend's Big-eared Bat (2), Big Brown Bat (49), Little Brown Myotis (82), Long- 

 legged Myotis (10), Western Small-footed Myotis (Myotis ciliolabrum) (3), Western Long-eared 

 Myotis (Myotis evotis) (4). One male Big Brown Bat, marked at the cave in October 1996, was 

 present in this sample. Significantly more males were present in netting samples of Big Brown 

 Bat, Little Brown Myotis, and Long-legged Myotis, species for which sample sizes were largest. 



Within species, especially Little Brown Myotis and Big Brown Bats, mean weights in 

 September were greater than in June or July. For Big Brown bats, weight declined in October, 

 perhaps indicating that late-flying individuals were still attempting to gain fat reserves prior to 

 hibernation. Alternatively, they may have been seeking additional opportunities for mating at the 

 expense of accumulated fat stores. 



Evidence of bat use was found in two of three rock-shelter caves examined. These caves 

 were shallow (21 m maximum depth), and are most likely used as night roosts. Numerous other 

 limestone pockets and rock-shelter caves, as yet unexamined for bat sign, could be used by bats. 

 Most old mine workings are no longer accessible to bats, but a few could provide significant 

 habitat and merit further examination. Most caves and mines of any size in the Little Rocky 

 Mountains are too cold for use as maternity roosts by bats. 



To date, seven species of bats (the six previously listed plus the Hoaiy Bat. Lashirus 

 cinereus) have been verified in the Little Rocky Mountains, and an additional species (Silver- 

 haired Bat, Lasionycteris noctivagans) has been reported, based on vocal recordings. A summary 

 of all records for each species is provided. 



Unauthorized human entiy into Azure Cave, especially if it occurs during the period of 

 occupancy, continues to be a management concern for protection of the bats using the cave as a 

 hibernaculum. Means to improve security of the gate (while maintaining accessibility for bats), 

 and regular visits to Azure Cave to check on gate integrity, should be considered. 



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