List of Mammals of Connecticut

This list of mammals of Connecticut includes both native and nonnative species (introduced or invasive) found in the state now or in the past, but not domesticated or farm animals.

Many mammals formerly extirpated in the state have returned, sometimes with active human projects and sometimes through a natural expansion from neighboring states as Connecticut's natural environment has become more welcoming to them.

Many mammal species were removed from Connecticut or almost became extinct within the state through hunting and clearing forests to create farmland, starting in the 17th century with European colonization and continuing until the 19th century, when most of the state's forest covering had been replaced with farmland. Populations of moose, turkeys, black bears and mountain lions lost their habitats and were greatly reduced or eliminated in Connecticut. Pollution in the 19th and 20th centuries also played a role in either greatly reducing or extirpating some species, such as the bald eagle.

With the collapse of farming in the 19th century and its continued decline in the state in the 20th century, forests spread back over much of the land. They are not the same forests, however: Chestnut trees, for instance, wiped out by a disease, are not nearly as prevalent as they once were, and the lack of their nuts affects the populations of various mammals. Stone walls, built largely in the nineteenth century, provide more welcoming homes to certain species; and mammals from Europe, including the house mouse and Norway rat, and from elsewhere (such as the coyote) can create a different competitive environment for some species and a different food source for some (the barn owl, for instance, can now feed on Norway rats).

To some extent, deforestation and fragmentation of forests has occurred in recent decades with expanded residential development. Some improvements have come with the removal of certain industries from Connecticut since the mid-20th century and the installation of more sewage treatment plants and improvements in their functioning. Residual industrial pollution remains, however, and prevailing winds keep Connecticut on the receiving end of pollution from the New York City metropolitan area and other areas south and west of the state, Connecticut also continues to produce some of its own pollution.

Dead animals killed by cars on the state's roads are one of the primary ways state residents see diverse varieties of local mammals. The more common roadkill in Connecticut consists of striped skunks, oppossums, raccoons, and gray squirrels.