Weasel | The Canadian Encyclopedia



The weasel is a small, long-bodied, carnivorous mammal of the family Mustelidae. Three species of weasels are found in Canada: the short-tailed weasel, also known as the ermine or stoat (Mustela erminea), the long-tailed weasel (Mustela frenata), and the least weasel (Mustela nivalis). The least weasel is the smallest species in the order carnivora. The genus Mustela also includes mink, black-footed ferret, and the introduced European ferret.

River Otter
Sea otters live on the wooded slopes of watercourses (artwork by Todd Telander).
Short-tailed Weasel
Weasels assume a white winter coat in northern regions (artwork by Claire Tremblay).
The fisher is a solitary hunter, secretive and seldom seen (artwork by Todd Telander).
The marten is an acrobatic weasel, spending much of its time in trees (artwork by Todd Telander).
Black-footed Ferret (Side View)
The black-footed ferret is likely the rarest land mammal in North Amercia (artwork by Todd Telander).


Weasels have dark brown upper bodies and tails and creamy white to orange underparts. They assume a white winter coat in northern regions. In the fur industry no distinction is made among the coats of the three species; all are marketed as ermine. The weasel's head is bluntly pointed and its ears are small and rounded. Weasels have long, slender bodies with thick necks and short feet.

Distribution and Habitat

Weasels live throughout mainland Canada from interior British Columbia to northern Ontario and  Quebec. They prefer coniferous forest or tundra but also inhabit marshes, meadows and broken woodlands.

Long-tailed weasels, the largest species, live in a range from South America to southern British Columbia, the Prairies, Ontario, Quebec and New Brunswick. They prefer mixed hardwood forest but also inhabit other forests or open country, always near water.

The short-tailed weasel, widespread in the northern hemisphere, lives throughout Canada in habitats including tundra, boreal forest, meadows and riverbanks. Least weasels are also widespread in Canada.

Reproduction and Development

Long-tailed weasels breed from July to August. Four to nine young are born 205-237 days later. Delayed implantation of the embryo accounts for the long gestation.

Short-tailed weasels mate in March; gestation lasts about 30 days and the single litter averages six young.

Least weasels breed throughout the year, with a 35-day gestation period. They bear two to three litters annually, with three to six young in each litter. Adulthood is reached at 120 days for females and 250 days for males.

In all species of weasel males may assist females in hunting food for the young.


All species of weasel eat small mammals and insects. Long-tailed and short-tailed weasels eat young rabbits and larger rodents as well. Least weasels are as small as the mice on which they prey.

Relationship with Humans

As efficient killers of mice, weasels are useful to farmers, except when they take poultry.

Other Members of the Weasel Family

Other members of the weasel family, Mustelidae, represented in Canada include the badgerfishermarten and  wolverine, the largest mustelid. There are three that spend some or most of their time in water: the mink and otter in freshwater, and the sea otter in saltwater.

Weasel Taxonomy













Species Found in Canada

M. erminea, M. frenata, M. nivalis

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External Links

Wolverine Distribution
Fisher Distribution
Marten Distribution