The family Vespertilionidae contains more bat species than any other group. Vespertilionids demonstrate a diversity of roosting sites including buildings, especially attic areas, caves, mines, fractures in rock, and hollowed locations or foliage roosts in trees. Fewer than 400 specimens of Idaho bats have been professionally prepared and deposited in natural history museums in the United States. Consequently, the distribution of each of the species is very poorly known. Many vespertilionids use abandoned or inactive mine sites, a condition that may gravely impact populations of individual species as old mine closures, now a national priority, increase. Closures are being mandated as a result of unstable and deteriorated conditions that endanger unsuspecting humans who do not understand their interest in exploring an old mine may lead to a tragic outcome.