 They are one of the last species to enter hibernation in the fall and the first to leave in the spring, with a hibernation period lasting from late November to early April.They have been found in very cold caves and mines and can tolerate lower temperatures than other bat species (Whitaker and Hamilton 1998).Unlike most other bat species, they often hibernate in caves and mines that are relatively short (150m) and they are most often found hibernating near the entrance where temperatures sometimes dip below zero and the humidity is low (Barbour and Davis 1969; Merritt 1987; Harvey 1992).