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Bats of Azure Cave and the Little Rocky Mountains, Montana

2000; Ottawa Field-Naturalists' Club; Volume: 114; Issue: 1 Linguagem: Inglês

10.5962/p.363917

0008-3550

Paul Hendricks, David Leon Genter, Sam. Martinez,

Environmental and Biological Research in Conflict Zones

During 1996-1998, we documented eight species of bats in the Little Rocky Mountains of Phillips County, north-central Montana, USA.: Western Small-footed Myotis (Myotis ciliolabrum), Western Long-eared Myotis (M.evotis), Little Brown Myotis (M.lucifugus), Long-legged Myotis (M.volans), Big Brown Bat (Eptesicus fuscus), Townsend's Big-eared Bat (Corynorhinus townsendii), Silver-haired Bat (Lasionycteris noctivagans), Hoary Bat (Lasiurus cinereus).Presence of Lasionycteris was based on recorded vocalizations, all other species were captured more than once (n = 212 total individuals).Six species (all but the last two listed above) were captured at the mouth of Azure Cave.Sex ratios in samples of the three most common species at Azure Cave (M.lucifugus, M. volans, E. fuscus) were significantly biased (P < 0.05) for males.Five species were captured at stock ponds, and two additional species were detected but not captured at water sources.Mean hibernation counts in Azure Cave during April 1997 and 1998 were 1246 and 1120 bats, respectively; mean count during November 1998 was 1604 bats.These counts indicate more than a doubling in the number of bats using the cave since the first complete count in April 1978, and make Azure Cave the largest bat hibernaculum known in Montana and one of the largest in the Pacific Northwest and northern Rocky Mountain regions.Four bat species have been documented in Azure Cave (M.lucifugus, M. volans, E. fuscus, C. townsendii), with Myotis spp.consistently comprising the majority of individuals.Counts of bats in Azure Cave from previous studies during various months indicate that the cave is not used as a maternity site, probably because the cave environment is too cold (about 6.5-7.5°Cthroughout the year).Annual emergence probably occurs in late May to early June, fall swarming probably occurs from late August to mid-September.Weight of E. fuscus and M. lucifugus increased from summer to fall, but late-flying E. fuscus in October weighed less than September individuals, possibly because they had yet to attain threshold fat reserves prior to hibernation, or perhaps as a trade-off for increased mating opportunities late in the breeding season.