Most active on cloudy, dark nights. Probably solitary throughout much of the year. In captivity, females aggressively exclude other females from the nest, and males fight during breeding season, but sexes may share nests outside of the breeding season. Pregnant females have been found from May through August. After a gestation of 19-24 days, litters are produced from June through September.
Young females tend to have smaller litters.
There is a maximum of 3 litters per yr. The altricial young are weaned at about 19 days. Females are capable of breeding in the first spring, but sexual maturity usually achieved in the second yr for both sexes. Predators include hawks, owls, coyotes, bobcats, and weasels. The mammals of Canada.