Summary of bat surveys conducted at abandoned and inactive mines of the Clearwater National Forest 2002–2004

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Abandoned and inactive mines are a safety concern and a liability for land managers. In order to reduce this hazard, the USDA Forest Service is considering closing inactive mines on the Clearwater National Forest. However, many species of bats rely on inactive mines for day and night roosts. Surveys were conducted in order to determine which abandoned and inactive mines are being occupied as roosts by bats. Mine sites were located by using topographic maps and an Idaho Geological Survey publication entitled Site Inspection Report for the Abandoned and Inactive Mines in Idaho on U.S. Forest Service Lands (Region 1)—Clearwater NF, Volumes I and II (Kauffman, Bennett and Mitchell 2000). Surveys were conducted on a total of 32 adits and/or shafts over a three-year time period (Table 1). Eleven other mines reported in the Kauffman Report were also considered for survey, but most of these 11 were dropped because they were found on active mining claims. A few of the adits were also dropped because they appeared to have little bat habitat potential (generally short lengths or shallow depths). At the end of the three-year survey, 17 adits and shafts were found to have bat activity (see Table 1 and individual mine summaries). Types of surveys used included external, observed emergence, remote detection, mist net, and harp traps. An ANABAT detector was used for acoustic sampling. We obtained 594 calls using the ANABAT detector. Species trapped or detected acoustically at the mine sites included long-legged myotis (Myotis evotis) and long-eared myotis (Myotis volans). The silver-haired bat (Lasionycteris noctivagans) was also identified acoustically, but it is unclear whether this species is actually using any of the mines. No silver-haired bats were trapped in mist nets. Of the 15 mines or shafts where no bat activity was recorded there were a few mines that stand out as possibly having habitat potential for bats. Negative results do not necessarily mean that the mines are not used. These mines include the following: K8109901 near Bluebell Creek: several bats were seen in the area, but none flew in or out of the mine during the survey; Mountain Gulch Adits 3 and 4: these adits are thought to be connected to a shaft which did have confirmed use; and the Mizpah Shaft: this shaft is deep with side adits that appear like they could have potential for bat habitat. One surveyed mine (Gold Dust – Adit 3/3a) was later confirmed to be collapsed by the Regional Mineral Examiner and is thought to have no bat habitat potential. Lodestone Peewee – Adit #2 and the Gold Dust Mother Lode adits are also thought to be collapsed, but collapse has not been confirmed by underground examination.

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ELECTRONIC FILE - Zoology: Mammals