Maternity and hibernation colonies typically are in caves and mine tunnels. Prefers relatively cold places for hibernation, often near entrances and in well-ventilated areas. In California, most limestone caves are too warm for successful hibernation; solitary males and small groups of females are known to hibernate in buildings in the central part of the state. Does not use crevices or cracks; hangs from the ceiling, generally near the zone of total darkness (Schmidly 1991). Uses caves, buildings, and tree cavities for night roosts. Throughout much of the known range, commonly occurs in mesic habitats characterized by coniferous and deciduous forests (Kunz and Martin 1982), but occupies a broad range of habitats (e.g., see Handley 1959). In California and Washington, known from limestone caves, lava tubes, and human-made structures in coastal lowlands, cultivated valleys, and nearby hills covered with mixed vegetation. On West Coast found regularly in forested regions and buildings, and in areas with a mosaic of woodland, grassland, and/or shrubland. Recorded from pine-fir- hemlock-broadleaf deciduous forest in western Oregon, and from the edge of spruce-fir forest in Colorado (see Handley 1959). In Texas, ranges from desert scrub to pinyon-juniper woodland, consistently in areas with canyons or cliffs (Schmidly 1991). In New Mexico, most commonly captured in evergreen forests during warm months, least commonly captured in xeric shrublands (see Kunz and Martin 1982). In Arizona, occurs in desertscrub, in shelters in desert mountains (where infrequent), oak woodland, pinyon-juniper, and conifer forests (Hoffmeister 1986). Apparently restricted in Kansas and Oklahoma to riparian communities and nearby gypsum caves in the mid-grass prairie region. Generally uncommon in prairies and extreme desert, although occurs in the lower elevations of the arid plateau and desert ranges of northcentral Mexico and the arid valleys south of the transverse volcanic belt. Known in Mexico mostly from relatively arid regions (e.g., grassy hills with nearby pine-oak woodland) but also from more humid localities with oak, pine, juniper, cypress, madrone, and manzanita (Handley 1959). Ozark and Appalachian populations inhabit caves mostly in oak-hickory forest (Handley 1959). Nimble; able to fly through narrow passages (Hoffmeister 1986). Females gather in small nursery colonies in the warm parts of caves or mines, sometimes in buildings (western U.S.). Individuals generally return to the same maternity roost in successive years. In Oregon, both sexes apparently use a series of interim roost sites between emergence from hibernation and the time females enter into maternity colonies, with little individual fidelity to these sites (Dobkin et al. 1995).