RESULTS AND DISCUSSION 



AZURE CAVE 



Hibernation Counts — Total counts of bat occupancy in Azure Cave were 1 174-1318 (mean = 

 1246) on 20 April 1997, 1101-1138 (mean = 1120) on 18April 1998, and 1457-1751 (mean = 

 1604) on 12 November 1998 (Figure 2). The count from November probably represents a 

 reasonable estimate of the numbers that would be present if a count were conducted in April 

 1999, assuming little movement in or out of the cave during winter. Therefore, the November 

 count is considered in this report as equivalent to counts obtained in early spring. 



The 1997-1998/1999 counts show a significant increase (Figure 2) in the number of bats 

 using Azure Cave as a hibernaculum since the first complete count (Chester et al. 1978). The 

 three counts reported above were consistently greater than 1 1 00 individuals, more than a 

 doubling of the previous high count of 1978. Counts with questionable figures are those of Butts 

 (1993), which was incomplete, and the MTNHP count of June 1996 (Hendricks and Genter 

 1997), which probably occurred after spring emergence had begun. Reasons for the dramatic 

 increase of hibernating bats in Azure Cave are unknown, but may relate to the frequency and 

 timing of disturbance by cave visitors in the past. There is some circumstantial evidence that 

 visitation was once more common than in the last 4-5 years. 



The number of bats hibernating in Azure Cave since winter 1996/1997 make it one of the 

 largest known bat hibernacula in the Pacific Northwest and Northern Rocky Mountains regions. 

 Azure Cave harbors more wintering bats than any reported hibernaculum in British Columbia 

 (Nagorsen et al. 1993), Oregon or Washington (Perkins et al. 1990), and Wyoming (Priday and 

 Luce 1997). Azure Cave is as large or larger than hibernacula reported from Alberta (Schowalter 

 et al. 1979, Schowalter 1980) and is about the size of the Jewel Cave hibernaculum in South 

 Dakota (Choate and Anderson 1997). Jewel Cave, however, is used by a much greater number of 

 Corynorhinus townsendii, as are some other hibernacula in Idaho and Wyoming (e.g., Genter 

 1986, Priday and Luce 1997) 



Counts of bats in Azure Cave conducted throughout the year, using data from all sources, 

 indicate a seasonal pattern of occupancy (Table 1). Apparently few bats use the cave for a roost 

 site between mid- June and late August. Ambient temperature in all portions of the cave beyond 

 the Big Room ranged between 43-45°F (6.5-7. 5°C) and 85-100% relative humidity during April 

 entries, and similar data were collected in June 1996, and by Chester et al. (1979) during August 

 1978. Temperature and relative humidity were somewhat lower at the top of the Big Room 

 during the period of hibernation, nearer the cave entrance. These data indicate Azure Cave 

 remains relatively cold year round, with little seasonal fluctuation in the two environmental 

 climate variables important for bats. Because of constant cold temperature, Azure Cave is not 

 suitable for use as a maternity roost. 



In the Little Rocky Mountains, most female Myotis lucifugus, M. volans, M. evotis, and 

 Eptesicus fuscus probably select buildings and tree snags or stumps for maternity roosts, as 

 indicated by studies elsewhere (e.g., Schowalter and Gunson 1979, Schowalter et al. 1979, 

 Vonhof and Barclay 1997, Ormsbee and McComb 1998). Female Corynorhinus townsendii 

 probably move from Azure Cave to other, warmer caves and rock crevices or abandoned mines 

 for use as maternity roosts (Humphrey and Kunz 1976, Dobkin et al. 1995, Clark et al. 1997). 



Hibernating bats were not present uniformly throughout Azure Cave. Between 88.8- 

 89.2% of the total count (based on room and total means) were found widely spread in the Lunch 



