Gestation is about three weeks. Newborn young are helpless and unfurred, but grow rapidly and reach adult size when 4-6 weeks old. For more specific life history information, see listings under each species. The masked shrew is the most widely distributed shrew in North America, ranging over almost all of the continent's northern half. It occurs throughout Pennsylvania.
Masked shrews molt twice a year.
In winter, they are dark brown to almost black on their upperparts, lighter brown or grayish on their underparts. Summer coloration is lighter and browner. Sorex cinereus closely resembles the slightly smaller pygmy shrew. Masked shrews inhabit wooded areas, living under rocks logs and in the leaf litter, often in swamps or along stream banks or spring runs. Rarely found in dry fields, they occasionally inhabit hedgerows and stone walls in open country.