Least Weasel - Mustela nivalis

The least weasel has a thin, very elongated and extremely flexible body with a small, yet elongated, blunt muzzled head which is no thicker than the neck. Its eyes are large, bulging and dark coloured. Its legs and tail are relatively short, the latter constituting less than half its body length. The feet are armed with sharp, dark claws, and the soles are heavily haired.

Least Weasel

The winter fur is dense, but short and closely fitting. In northern subspecies, the fur is soft and silky, but coarse in southern forms.

This species' dimensions vary geographically, to an extent rarely found among other mammals. Least weasels of the vulgaris group, for example, may outweigh the smaller races by almost four times. In some large subspecies, the male may be 1.5 times longer than the female. Variations in tail length are also variable, constituting from 13-30% of the length of the body. Average body length in males is 13–26 cm, while females average 11.5–20.5 mm. The tail measures 1.2–8.7 cm in males and 1.7–6.0 cm in females. Males typically weigh 36-250 grams while females weigh 29.5-117 grams.

Weasels tolerate a wide range of habitats, including forests, farmlands and cultivated fields, grassy fields and meadows, riparian woodlands, hedgerows, alpine meadows and forests, scrub, steppe and semi-deserts, prairies, and coastal dunes. This species occurs from sea level to at least 3,860 m.

Least Weasel

It forms dens in crevices among tree roots, in hollow logs, or in abandoned burrows of other species. This species is a specialist diurnal predator of small mammals (especially rodents), although it will also occasionally feed on birds’ eggs, lizards, frogs, salamanders, fish, worms, and carrion. Food may be stored for the winter. Habitat selection is usually determined by local distribution of rodents. Foraging individuals avoid open spaces, where they are most vulnerable to predation by raptors. They prefer dense, rank grassland where microtines (voles and lemmings) are abundant. In the wild, most least weasels do not live more that 3-4 years.

In the European part of its range, there are documented population declines in some areas (e.g. Britain), and suspected declines in others. Throughout Eurasia, it is relatively common, but not often seen. Local densities of 0.2 to 1.0 individuals per hectare can occur in favored habitats when prey are abundant. However, over wider areas, the average density may be as low as 1 to 7 per 100 hectares. Populations fluctuate both seasonally and annually, sometimes involving large increases of up to 10-fold, concurrently or within 9 months of a population peak of small rodents, and lasting 6 to 18 months.

The population trend is believed to be stable globally.

• Afghanistan
• Albania
• Andorra
• Armenia
• Austria
• Azerbaijan
• Belarus
• Belgium
• Bosnia and Herzegovina
• Bulgaria
• China
• Croatia
• Czech Republic
• Denmark
• Estonia
• Finland
• France
• Georgia
• Germany
• Greece
• Hungary
• Iran
• Iraq
• Israel
• Italy
• Japan
• Kazakhstan
• Kosovo
• Kyrgyzstan
• Latvia
• Liechtenstein
• Lithuania
• Luxembourg
• Macedonia
• Malta
• Moldova
• Monaco
• Mongolia
• Montenegro
• Netherlands
• Norway
• Poland
• Portugal
• Romania
• Russia
• San Marino
• Serbia
• Slovakia
• Slovenia
• Spain
• Sweden
• Switzerland
• Syria
• Tajikistan
• Turkey
• Turkmenistan
• Ukraine
• United Kingdom
• Uzbekistan

This species has a circumboreal, Holarctic distribution, taking in most of Eurasia. It has been introduced in Malta, Crete and the Azore Islands. It is found throughout Europe including Britain (but not Ireland), and all major Mediterranean islands. The populations on the Azores and Mediterranean islands (Malta and Crete) are widely considered to be introduced.

Least Weasel

Threats include incidental poisoning with rodenticides and persecution. The weasel prefers open agricultural habitats, which are declining owing to changes in agricultural practices (rural abandonment) in parts of Europe, as open fields undergo succession.