Scientific Name: Mustela vison
The mink is a large, brown, semi-aquatic weasel. Males are 20 – 24 inches long, females about one-fifth smaller. The tail is less than half the length of the body. Weights range about 3 ½ pounds. Mink are dark brown, slightly paler beneath, with the tip of the tail nearly black. Their toes are partially webbed.
Mink live statewide in Colorado but are most abundant in the mountains, near beaver ponds. The beaver pond provides still-water habitat and an abundance of food on the plains.
Mink live in burrows, dens of muskrats or tree hollows but are only weak burrowers.
Mink primarily eat muskrats, nestling waterfowl, frogs, salamanders, fish, beaver kits and insects; crayfish may be a staple when in-season. Mink kill more food than they can eat at once, and excess food is stored, especially in winter.
Breeding occurs in summer, but implantation of embryos is delayed. Gestation takes five to ten weeks, with one to six (usually four) young born in April or May. Newborns are tiny, but grow quite rapidly, doubling their weight five or six times to reach 40 percent of adult weight by the time they wean at seven weeks of age.
Although coyotes, red foxes or great horned owls occasionally kill them, combat with other mink is a greater cause of death than all predators combined. Beyond that, the leading cause of mortality for minks is the harvest by humans for their beautiful winter fur.
By David M. Armstrong Department of Ecology & Evolutionary Biology Environmental Studies Program, University Museum of Natural History University of Colorado-Boulder