Habitat
These bats occur in various habitats, including sea coasts, desert scrub, oak-juniper woodlands, montane and humid coastal forests, mountain meadows, canyons, riparian woodlands, grasslands, rural residential areas, and towns (Barbour and Davis 1969, Hoffmeister 1986, Simpson 1993, Nagorsen and Brigham 1993, Verts and Carraway 1998, Oliver 2000, Adams 2003, Falxa 2007). Night roosts are in a wide range of sheltered sites, including trees, shrubs, mines, caves, bridges and buildings (Krutzsch 1954, Barbour and Davis 1969, Hirshfeld et al. 1977). They roost by day in crevices of various kinds, including rock fissures, tree cavities, spaces behind loose tree bark, and nooks in bridges and buildings; occasionally they roost on small desert shrubs or on the ground (Barbour and Davis 1969, Nagorsen and Brigham 1993, Simpson 1993, Barclay and Brigham 2001). Hibernation sites include caves (including lava tubes), mines, tunnels, or buildings; often in buildings in the Pacific Northwest (Senger et al. 1974, Perkins et al. 1990, Nagorsen and Brigham 1993). Maternity colonies are in rock crevices, tree cavities, under bark (Brigham et al. 1997, Barclay and Brigham 2001, Vonhof and Gwilliam 2007), or in crevices of bridges or buildings. Reproductive females often change roost sites among different trees (Brigham et al. 1997). Foraging occurs in a wide range of habitats: over meadows/grassland, shrubland, and wooded areas; over water; and around street lights (e.g., see review by Oliver 2000).
Ecology
In summer, these bats roost alone or in small groups of usually not more than 25 individuals (Simpson 1993). Reproductive females in tree-dwelling populations form small colonies averaging about 10-20 individuals (range = 4-52) (Brigham et al. 1997, Barclay and Brigham 2001, Vonhof and Gwilliam 2007). Males and females roost separately in summer.
Reproduction
Breeds in late fall in most of range, or early spring in California. Females give birth to single young, late May to mid-June (Barbour and Davis 1969), in late June or July in Canada (Banfield 1974, van Zyll de Jong 1985, Nagorsen and Brigham 1993). In southwestern California, no pregnant females were found after mid-June. Pregnant and lactating females have been found in Texas in mid- to late May (Ammerman et al. 2012). Individual females produce one young per year. Potential reproductive lifespan is 15 years (Duke et al. 1979). Colonies usually are small, up to about 25 individuals.