Mustela vison

Order: Carnivora
Family: Mustelidae

Status: This valuable furbearer is one of the most widespread carnivores in North America.  Official Montana furbearer managed and protected by regulated fur harvest seasons.

Identifying Characteristics: This medium-sized, semi-aquatic carnivore has a long, thin body; short, sturdy legs; short, pointed nose; short, rounded ears, and a dorsoventrally flattened head.  Thickly furred tail.  Usually rich dark brown in color with a white chin patch.  Sometimes white spots on belly.  Fur is soft and lustrous with long, glossy guard hairs.  Dense pelage is its only obvious aquatic adaptation.  Total length: 19 to 28 inches.  Weight: 1.5 to 2 pounds.

Habitat: Usually found along streams and lakes.  Commonly occurs in marshes and beaver ponds.  Permanence of water and dependable source of food are most important habitat components.  Often uses den sites of other animals and is commonly found in association with muskrats.

Food Habits: Preys primarily on small mammals, birds, eggs, frogs, and fish.  Its diet is almost entirely animal.  During summer preys on waterfowl.

 Life History: Semi-aquatic forager.  Can kill prey larger than itself.  Chiefly nocturnal, territorial, and secretive.  Dens underneath piles of brush or driftwood, under rocks, in hollow logs, and in houses or dens abandoned by beavers or muskrats.  Very aggressive mating behavior.  Mates from January through March; 40 to 79 day gestation; delayed implantation; young born during April or May; averages 4 to 5 per litter.

Similar Species: Weasel - has white or yellow underparts.  Marten - has buffy patch on throat and breast.  River otter - much larger.

STATEWIDE SEASON DATES: November 1 - April 15 of the following year except state Wildlife Management Areas and specific closures (See SPECIAL REGULATIONS). Limit: None.