A Amarican marton weasel has a long slender body covered in glossy brownish fur with a lighter coloured throat, a long bushy tail and a pointed snout. Like those of cats, its claws are semi-retractable, and aid it in climbing trees. It also has very large foot pads in relation to body weight allowing it to walk on hard snow. This provides the marten with a distinct advantage in areas that receive heavy snows. The animal is omnivorous, preferring to catch and eat small mammals, but readily consuming fish, frogs, insects, carrion, and fruit and other vegetation when available. It is most active at night, early morning, and late afternoon. It is usually solitary outside of the mating season. Males defend a territory of one to three square miles, and can be very aggressive toward other males. Mating occurs during the summer, but implantation of the fertilized egg is delayed (delayed implantation) and 1 to 5 young "kits" are born the following spring in a den in a hollow tree or rock cavity.