They have a long slender body with long shiny fur. Their fur is light brown to black with a cream colored patch on their chest. Their legs and tail are dark brown to black, and they have a gray colored head.
Females are usually smaller and lighter in color.
Martens are opportunistic feeders, and prey on small mammals such as squirrels, mice, voles, chipmunks, snowshoe hares and occasionally birds. They will also feed on insects, fruits, nuts and carrion. A favorite prey is the red squirrel. Martens are solitary and nocturnal animals, but usually feed during the day when prey is most abundant. They are somewhat arboreal and spend much of their time dwelling in trees, but are also at home in the water.