The native mammals of Massachusetts are as varied as the topography of this beautiful state in the northeastern United States. As of February 2009, the Massachusetts Division of Fisheries and Wildlife states that 60 native mammals were potentially present in the state. This number does not include the dozens of additional species that are vagrant or were introduced to Massachusetts. The native mammals in the state are all placental and can be classified by their commonly favored land or marine habitats.

Woodlands in Massachusetts consist of mixed forests that have areas of predominantly coniferous or deciduous trees. Native mammals that often prefer coniferous regions include red and flying squirrels, snowshoe hares, moose and fishers. Opossums, gray squirrels, chipmunks, deer mice, red and gray foxes, white-tailed deer, porcupines, and several species of bats are often seen in deciduous areas. Coyotes favor bushy scrub locations. Black bears frequent both coniferous and deciduous habitats. While people fear them, they usually do not attack humans but prefer to run away into the woods.

Grassland areas in Massachusetts include fields, meadows and farmland. Native mammals that prefer grassland habitats include moles, skunks, cottontail rabbits, voles and woodchucks. Native mammals that favor grassy areas often appear on lawns and in back yards of suburban homes and are usually considered pests. Cottontails are declining in numbers because of the decrease in their favored habitats, such as farmland and pastures, in the state.

Bogs, marshes, intertidal shores, wet meadows and swamps typify the wetland areas of Massachusetts. There are wetland areas throughout the state. Some native mammals that include wetlands among their favored habitats are muskrats, ermine, shrews, jumping mice, lemmings and bobcats. Among other habitats, lemmings frequently favor cranberry bogs. Bobcats roam wooded and scrub areas as well as swampy terrain near fields. They are the only wildcat presently found in Massachusetts and are very shy and elusive.

There are many rivers, ponds and lakes of all sizes in Massachusetts. The native mammals that most enjoy these habitats include minks, river otters and beavers. Weasels frequent various habitats but prefer to be close to water. River otters are found mainly near water but will sometimes wander far into forested locales. Beavers build dams and lodges with multiple entrances in freshwater areas such as ponds, rivers and lakes.

Numerous harbors and coves dot the Atlantic coastline of Massachusetts. Native mammals in these waters include harbor seals, harbor porpoises and several species of dolphins. There are many species of whales in the outer harbors and Atlantic coastal waters off Massachusetts, including killer, beluga and pilot whales. Endangered whales seen in these waters are the humpback, fin, sperm and northern right whales.