Abandoned mines have become significant bat roosting sites worldwide, but they can be extremely hazardous when entered by curious people. Tons of rock periodically fall from the ceiling of this Wisconsin iron mine, yet it also provides hibernation sites for over 100,000 bats of four species. Many states have begun large
-scale programs to close or "reclaim" mines as a public safety measure, usually without conducting surveys to check for bat populations (story, page 13). Driven from their traditional cave roosts by human disturbance, cave-dwelling bats now have little or no choice but to live in abandoned mines, which are now key to their survival.