Habitat
Buildings and other structures in cities, villages, and farm country, also dumps and open areas near abundant food. Most common in colder climates of high latitudes; in warmer regions restricted to habitats highly modified by humans (Musser and Carleton, in Wilson and Reeder 1993). In Hawaii: locally common in some lowland cane fields, rare or absent in extensive grassland and most native forests (Tomich 1986). In Oklahoma, moved from fields to buildings in fall (Caire et al. 1989). Young are born in nests in buildings, under debris, or underground.
Ecology
Home range is usually less than an acre. Can become locally abundant. Lives in highly organized colonies. Throughout range in different habitats, median survival time relatively consistent at about 3 months, annual survival rate at about 5%.
Reproduction
Breeds throughout the year, particularly from spring to fall. Gestation lasts 21-24 days or up to a week longer in lactating females. Litter size is 2-14 (average about 9). Averages 6 litters per year (range 3-12). Sexually mature in 80-85 days.