The mink (Mustela vison, Fig. 1) is a member of the weasel family. It is about 18 to 24 inches (46 to 61 cm) in length, including the somewhat bushy 5- to 7-inch (13- to 18-cm) tail, and weighs 1 1/2 to 3 pounds (0.7 to 1.4 kg).
Females are about three-fourths the size of males. Both sexes are a rich chocolate-brown color, usually with a white patch on the chest or chin, and scattered white patches on the belly. The fur is relatively short, with the coat consisting of a soft, dense, underfur concealed by glossy, lustrous guard hairs. Mink also have anal musk glands common to the weasel family, and can discharge a disagreeable musk if frightened or disturbed. Unlike skunks, however, they cannot forcibly spray musk.
Figure 1. The mink, Mustela vison, is a semiaquatic furbearer well known for its high-quality fur.
General Biology, Reproduction, and Behavior
Mink are polygamous and males may fight ferociously for mates during the breeding season, which occurs from late January to late March. Gestation varies from 40 to 75 days with an average of 51 days. Like most other members of the weasel family, mink exhibit delayed implantation; the embryos do not implant and begin completing their development until approximately 30 days before birth. The single annual litter of about 3 to 6 young is born in late April or early May and their eyes open at about 3 weeks of age. The young are born in a den which may be a bank burrow, a muskrat house, a hole under a log, or a rock crevice. The mink family stays together until late summer when the young disperse. Mink become sexually mature at about 10 months of age.
Mink are active mainly at night and are active year-round, except for brief intervals during periods of low temperature or heavy snow. Then they may hole up in a den for a day or more. Male mink have large home ranges and travel widely, sometimes covering many miles (km) of shoreline. Females have smaller ranges and tend to be relatively sedentary during the breeding season.
Range and Habitat
Mink are found throughout North America, with the exception of the desert southwest and tundra areas (Fig. 2). Mink are shoreline dwellers and their one basic habitat requirement is a suitable permanent water area. This may be a stream, river, pond, marsh, swamp, or lake. Waters with good populations of fish, frogs, and aquatic invertebrates and with brushy or grassy ungrazed shorelines provide the best mink habitat. Mink use many den sites in the course of their travels and the availability of adequate den sites is a very important habitat consideration. These may be muskrat houses, bank burrows, holes, crevices, log jams, or abandoned beaver lodges.
The mink is strictly carnivorous. Because of its semiaquatic habits, it obtains about as much food on land as in water. Mink are opportunistic feeders with a diet that includes mice and rats, frogs, fish, rabbits, crayfish, muskrats, insects, birds, and eggs.
Edward K. Boggess. Wildlife Program Manager. Minnesota Department of Natural Resources. St. Paul, Minnesota 55155