Bats have been moving into abandoned mines for about as long as miners have been packing up their picks and shovels to go in search of more promising diggings. Centuries of miners have left thousands of miles of underground passageways spiderwebbed beneath the surface of North America and much of the world. Bats use many of them for hibernating, for courtship and mating, for giving birth and rearing young, for night roosting, and as crucial rest stops on their migratory journeys.
Mines have become critical as traditional bat habitats disappear with alarming frequency. Cities encroach on natural caverns, while big, old hollow trees vanish from the forests. Old mines have become homes of last resort for millions of bats that represent 28 of the 46 bat species in the United States.
In the American West, some species, including Townsend’s big-eared bats (Corynorhinus townsendii) and California leaf-nosed bats (Macrotus californicus), often depend on abandoned mines for their very survival. In eastern states, abandoned mines house some of the largest known populations of such endangered species as the Indiana myotis (Myotis sodalis). Our understanding of the intricate ways in which bats use mines continues to grow as researchers study the complex interactions between bats and mines.
A decade ago, many of North America’s largest remaining bat populations were severely threatened by plans to close thousands of bat-occupied mines on federal, state, and private lands because of safety concerns. BCI and the U.S. Bureau of Land Management created the Bats and Mines Project in 1994 to protect mine-dwelling bats. By building local partnerships with an array of federal and state agencies, private organizations, and leading mining companies, the project has installed bat-friendly gates on more than 1,000 old mines. Local and national caver groups have contributed thousands of hours of labor.
Once, countless bats were trapped inside mines that were blasted or bulldozed shut. Now, thanks to BCI’s Bats and Mines Project, pre-closure surveys are almost routine and thousands of mines have become bat sanctuaries. As a direct result, the endangered Indiana myotis is now showing real signs of recovery. The Townsend’s big-eared bat, which had seemed destined for a spot on the endangered list a decade ago, is growing in numbers in many areas. Approximately 200 of its most important roosts are now protected as mine sanctuaries.