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  Carnivora · Mustelidae · Mustela nivalis

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Mustela nivalis

Least Weasel

Order: Carnivora
Family: Mustelidae

Click to see adaptations.   
Image of Mustela nivalis
Mustela nivalis - winter (white) coat, left; summer (brown) coat, right
Click to enlarge. (46 kb)

Conservation Status: Least Concern.

The smallest carnivores usually burn energy the fastest and have the most active lifestyles, so it is no surprise that the Least Weasel, the miniature among mustelids, consumes roughly half its body weight each day—equal to about two deer mice and a vole. As with other weasels, adult females may be half the size of adult males, and they mature much more rapidly; females are sexually mature at four months, males at eight months. Females produce two litters each year, unlike the larger, slower-breeding Ermine and Long-tailed Weasel. In the north, the fur of the Least Weasel turns from brown to white in winter, camouflaging them in the snow.

Also known as:
Weasel, Dwarf Weasel, Pygmy Weasel, Mouse Weasel

Sexual Dimorphism:
Males are larger than females.

Range: 180-205 mm males; 165-180 mm females

Range: 40-55 g males; 30-50 g females


Linnaeus, C., 1766.  Systema Naturae per regna tria naturae, secundum classis, ordines, genera, species cum characteribus, differentiis, synonymis, locis, Twelfth Edition, p. 69.  Laurentii Salvii, Uppsala, 1:1-532.


Mammal Species of the World (opens in a new window).

Mammalian Species, American Society of Mammalogists' species account *
* PDF reader available here (opens in a new window).

Distribution of Mustela nivalis

Image of Mustela nivalis
Click to enlarge. (95kb)

Skull of Mustela nivalis
Click to enlarge. (15kb)

Bones and Teeth

Mustela nivalis
Right lower carnassial tooth (second from left), with adjacent molar (far left) and three adjacent premolars (right). Click to enlarge. (6kb)

Mustela nivalis
Left upper carnassial tooth (second from left), with adjacent molar (far left) and two adjacent premolars (right). Click to enlarge. (9kb)