Peromyscus leucopus

Adults are reddish brown (juveniles gray), with a white belly, white feet, membranous ears, and bicolored tail (usually not sharply bicolored); adult total length 145-205 mm, tail 62-97 mm (usually shorter than head and body), hind foot 18-24 mm, ear 13-19 mm; 16-29 g in the northeastern U.S.; 3 pairs of mammae (Hall 1981, Godin 1977, Paradiso 1960).

Often difficult to distinguish from P. MANICULATUS. In New England, differs from MANICULATUS by having coarser and redder pelage, a more well-defined mid-dorsal stripe, a tail that is less distinctly white on the ventral surface and that seldom is as long as the head and body, and a broader rostrum (Godin 1977). See Hoffmeister (1986) for differences from PEROMYSCUS species in the southwestern U.S.

Prefers woodland edges, brushy fields, clearcuts, riparian zones; primarily a forest dweller. In Pennsylvania, abundance increased with forest fragmentation (Yahner 1992), and in Indiana density was highest in forest patches of less than 2 ha (Krohne and Hoch 1999). In Ohio, summer habitats included roadsides, crop fields, and farmsteads; these may act as dispersal corridors between wooded habitats (Cummings and Vessey 1994). In Indiana, few mice dispersed through grassland or agricultural fields surrounding forest patches (Krohne and Hoch 1999). Nests are placed in a variety of sites; underground (especially in winter), under debris, in building, in log or stump, in tree cavity, in old squirrel or bird nest, or in bird nest box.

Home range is about 0.1-0.2 ha, may range from a few hundred to a few thousand sq m, depending on circumstances. Territorial behavior is most prevalent at high population densities.

Population density ranges up to about 40/ha, sometimes up to 100+ per ha (see Kirkland and Layne 1989). In Virginia, adult density ranged from 22.9/ha in March to 0.3/ha in November of the following year (Terman, 1992, J. Mamm. 74:678-687). In Virginia, populations were highest in the year following a large mast crop (Wolff 1996, J. Mamm. 77:850-856).

Demographic unit may occupy 2.4-13.5 ha; small units may often undergo winter extinction (Krohne and Baccus 1985). Males tend to disperse from natal area before their first breeding season (may overwinter communally before dispersing); some females may remain and breed in natal range (Kirkland and Layne 1989).

This species does not disperse particularly well over water and is not a good colonizer of barrier islands (Loxterman et al. 1998).

More communal in winter than at other times; several may share single nest.

Young generally are born March-December in the north (spring and fall peaks, mid-summer and/or winter lull in many areas), all year in southern Texas and probably in Oklahoma (and probably other areas with similar climate). Gestation 22-25 days, longer if female is lactating. Litter size averages 4-5 in the north, 3-4 in the southern U.S. Young are weaned in about 3 weeks. Sexually mature in about 5-7 weeks; young of year may enter breeding population in fall. Most live only a few months; few live more than 1 year. Mating system ranges from promiscuity to facultative monogamy. Male may share nest with female until parturition. (Kirkland and Layne 1989).