Colonies of these bats roost in clusters among neighboring and nearby mature trees of densely to sparsely stocked forest stands (Whitaker and Hamilton 1998). Roost trees may also be isolated in pastures, in other open areas, or in flooded conditions. They commonly roost under tree bark, or in crevasses or cavities of trees, apparently preferring the loose bark of dead trees.

NATURE SERVE GLOBAL HABITAT COMMENTS:

Hibernates in caves; maternity sites are in trees.

In hibernation, limestone caves with pools are preferred. Hall (1962) noted that preferred caves are of medium size with large, shallow passageways. Roosts usually are in the coldest part of the cave. Preferred sites have a mean midwinter air temperature of 4-8 C (tolerates much broader range) (Hall 1962, Henshaw and Folk 1966), well below that of caves that are not chosen (Clawson et al. 1980). Roost site within cave may shift such that bats remain in the coldest area (Clawson et al. 1980); may move from a location deeper in the cave to a site nearer the entrance as the cold season progresses; moves away from areas that go below freezing. Hibernation in the coldest parts of the cave ensures a sufficiently low metabolic rate so that the fat reserves last through the six-month hibernation period (Henshaw and Folk 1966, Humphrey 1978). Relative humidity in occupied caves ranges from 66 to 95% and averages 87% throughout the year (Barbour and Davis 1969, Clawson et al. 1980). Because of these requirements, M. SODALIS is highly selective of hibernacula.

In summer, habitat consists of wooded or semiwooded areas, mainly along streams. Solitary females or small maternity colonies bear their offspring in hollow trees or under loose bark of living or dead trees (Humphrey et al. 1977, Garner and Gardner 1992). Humphrey et al. (1977) determined that dead trees are preferred roost sites and that trees standing in sunny openings are attractive because the air spaces and crevices under the bark are warmer. In Illinois, Garner and Gardner (1992) found that typical roosts were beneath the exfoliating bark of dead trees; other roost sites were beneath the bark of living trees and in cavities of dead trees. Kurta et al. (1993) found a large maternity colony in a dead, hollow, barkless, unshaded sycamore tree in a pasture in Illinois. In Michigan, a reproductively active colony occupied eight different roost trees (all green ash), all of which were exposed to direct sunlight throughout the day; bats roosted beneath loose bark of dead trees (Kurta et al. 1993). In western Virginia, a male used a mature, live, shagbark hickry tree as a diurnal roost; the bat foraged primarily among tree canopies of an 80-year-old oak-hickry forest (Hobson and Holland 1995). In Missouri, primary maternity roosts were in standing dead trees exposed to direct sunlight; there were 1-3 primary roosts per colony; alternate roosts were in living and dead trees that typically were within the shaded forest interior (Callahan et al. 1997). See Garner and Garner (1992) for detailed information on summer habitat in Illinois. Though maternity sites have been reported as occurring mainly in riparian and floodplain forests (Humphrey et al. 1977, Garner and Gardner 1992), recent studies indicate that upland habitats are used by maternity colonies much more extensively than previously reported. Garner and Gardner (1992) reported that 38 of 51 roost trees in Illinois occurred in uplands and 13 trees were in floodplains. Of the 47 trees in forested habitat, 27 were in areas having a closed (80-100%) canopy, and 15 were in areas having an intermediate (30-80%) canopy. A single roost tree was found in the following types of habitat: a heavily grazed ridgetop pasture with a few scattered dead trees, a partially wooded swine feedlot, a palustrine wetland with emergent vegetation, a forested island in the Mississippi river, and a clearcut around a segment of an intermittent stream where dead trees were retained for wildlife. Roosts were not found in forests with open canopies (10-30%) or in old fields with less than or equal to 10% canopy cover.

Roost trees include slippery elm (ULMUS RUBRA), American elm (ULMUS AMERICANA), northern red oak (QUERCUS RUBRA), post oak (QUERCUS STELLATA), white oak (QUERCUS ALBA), shingle oak (QUERCUS IMBRICARIA), shagbark hickory (CARYA OVATA), bitternut hickory (CARYA CORDIFORMIS), sweet pignut hickory (CARYA OVALIS), silver maple (ACER SACCHARINUM), sugar maple (ACER SACCHARUM), cottonwood (POPULUS DELTOIDES), green ash (FRAXINUS PENNSYLVANICA), and sassafras (SASSAFRAS ALBIDUM) (Cope et al. 1974, Humphrey et al. 1977, Garner and Gardner 1992). See Garner and Gardner (1992) for a detailed description of tree characteristics.

In Illinois, Indiana bats used the same, evidently traditional, roost sites in successive summers. Recapture of the same individuals within traditional roost sites during subsequent summers suggests site fidelity (Garner and Gardner 1992).