Sometimes called the American Marten or the Pine Marten, this member of the weasel family is typical with a long, slender body and pointed face, beautiful, silky fur and a long bushy tail. Its legs are longer and its tail bushier than weasels. Its color is variable but usually brown to almost black on top, sometimes a yellowish brown on top, while underneath it is dark except for a creamy white to orange throat patch. Its legs and feet are usually black. Its tail, about one-third its body length, is very dark. An expert tree climber, it has longer legs than most members of the weasel family and semi-retractile claws. Total length is 18 to 26 inches (460-660 mm), tail length is 5.4 to 6.4 inches (135-160 mm), and they weigh 1 to 3 pounds (400-1400 g).
It ranges throughout Canada and Alaska in the northern boreal forest, and south through the Rockies and Sierra Nevada ranges, and into the northern Great Lakes Region, and northern New England.
It is usually found in dense, deciduous, mixed, and especially in coniferous upland and lowland forests. In Idaho it is usually found in conifer forests, which include fallen logs, stumps and shrubs. It may use rocky alpine areas. In the central Rockies, it is associated in winter mainly with old-growth forests. An Idaho study found the species used a variety of forest types, but greatest activity was in older stands of spruce-fir.
Diet consists mainly of small mammals such as red squirrels and chipmunks, which they often capture by climbing up into trees to prey on. They also eat red-backed voles and meadow voles, and even snowshoe hares, plus birds, insects, and carrion. An Idaho study found that voles were a primary item in their diet. They also eat berries in the late summer. A Grand Teton study showed that from analyzing food items in scats, small mammal remains were found in 90.2 %, birds in 7.2%, insects in 17.4 %, and fruit and berries in 6.2% of the scats analyzed.
In the late 1800's the marten was abundant in the United States, but a tendency toward curiosity that exposes it to easy trapping led to its rapid decline. Heavy trapping nearly decimated the species by the turn of the century. In Europe, royalty commonly wore the fur of the sable, the marten's European (Old World), close relative. Martens are territorial animals. A study in Grand Teton National Park showed that males had territories of 0.9 square miles (2.3 square kilometers), and females had territories of 0.4 square miles (1.1 sq. kilometers). Males and females excluded other members of their gender from their territories, but a male's territory usually overlapped with one to several female territories. Activity may peak at dusk and dawn in summer; individuals have been frequently observed by day in winter. In the Sierra Nevada, foraging activity was observed to be nocturnal in winter, diurnal in summer, and apparently synchronous with activity of prey. For many years the marten was thought to be a primary predator on red squirrels and that they foraged mainly in trees. However, recent studies have shown that they forage primarily on the ground, but also in trees. There is evidence that they track and ambush prey, they use hunting perches, and they rob bird nests. When they are inactive, they occupy holes in dead or live trees, or in abandoned squirrel nests, in the dense crown of conifers, rock piles, burrows, or snow cavities; in winter they mainly use subnivean (under the snow) sites, often associated with coarse woody debris. Densities of l-2/km2 have been recorded in early fall. Some studies suggest species is old-growth dependent. A northern Idaho study of habitat use was initiated in 1995 by the Idaho Dept. Fish & Game. An early naturalist attributed "sky diving" to martens. Snow tracking provides evidence that, when descending a tree, they will occasionally leap out and away from the tree into the snow, often from a height of several meters. One study has reported several marten vocalizations, including huffs, growls, screams, and even chuckles.
Females achieve estrus during mid-summer, when they frequently scent mark their territory by urinating often and rubbing abdominal glands on sticks, rocks and logs. Breeding occurs after a courtship period that may last up to 15 days. Interestingly, the fertilized eggs are held in an arrested state of development until February or March, when they implant into the uterus. About 25 to 28 days later the young are born. This "delayed implantation" occurs in most other members of the weasel family, as well as in bears. The young weigh only about one ounce (30 g) at birth, weaning begins by week 6 or 7, and by 3 months they are nearly full grown and on their own. Young become sexually mature in their second year.
Important State References:
Koehler, G.M. and M.G. Hornocker. 1977. Fire effects on marten habitat in the Selway-Bitterroot Wilderness. J. Wildl. Manage. 41:500-505.