The mink is larger than the weasel and is usually dark brown with a white throat patch. It has a large, bushy tail that is often slightly darker than the body. Its dark fur has a beautiful sheen; its fur has brought recognition to the mink for many years. Many people have “stylishly” worn their mink coat. Mink are well adapted to their semi-aquatic riparian habitat. Their fur sheds water easily and they have partially webbed feet. They are very good swimmers. Total length is 19 to 28 inces (470-690 mm), tail length is 6.2 to 8.8 inches (154-220 mm), and they weigh 2 to 3.5 pounds (0.9-1.6 kg).
The mink is found throughout Alaska and Canada and most of United States except in the desert Southwest.
They prefer forested, permanent, or semi-permanent wetlands with abundant cover, marshes, and riparian zones. They are rarely found away from water. In Idaho, they prefer aquatic habitats at lower and middle elevations.
Mink uphold the reputation of the weasel family as predators. They prey on fish, crayfish, and frogs, which they capture while swimming. In some areas they rely heavily on muskrats for food. During the summer, up to 50% of their diet is crayfish and muskrats, but they will also take waterfowl and even meadow voles. In winter they rely less on aquatic food by continue to eat muskrats and occasionally a rabbit. When food is abundant they will cache it. A researcher in Illinois discovered a mink food cache of 13 muskrats, 2 mallard ducks, and 1 coot. Mink are also good fishermen; they have been observed “herding” small schools of fish into shallow water where they could capture the fish and eat them.
Mink are mainly nocturnal and crepuscular. They may reduce activity in severe winter weather. When inactive, they occupy dens in muskrat burrows, abandoned beaver dens, hollow logs, holes under tree roots, or a self-constructed burrow in a stream bank. Individuals are solitary, except during mating period and when females have young. Their home ranges are almost linearly associated with watercourses, usually about 20 to 50 acres (8-20 ha.) Male home ranges are considerably larger than that of a female. In good habitat, density may be 9 to 22 per 2.6 km2; higher concentrations indicate abundant prey.
Mink breed from late February until early April. They give birth from early May into July. This Gestation of 40 to 80 days (average 51) is shorter than most weasels but delayed implantation does occur in Mink. The embryo develops in about a month. Once the average litter of 4 to 5 young are born they develop rapidly. Young mink acquire deciduous teeth early and eat some meat by 25 to 30 days. They are weaned at 5 to 6 weeks, and they are hunting with the mother at about 8 weeks. Males may sometimes help care for young.
Important State References:
Whitman, J.S. 1981. Ecology of the mink (Mustela vison) in west-central Idaho. M.S. Thesis, Univ. Idaho, Moscow. 101pp.