Least Weasel, Weasel
Value of species
Game (hunting) species
Mustela nivalis nivalis Linnaeus, 1766
Mustela nivalis rossica Abramov & Baryshnikov, 1999
Mustela nivalis vulgaris Erxleben, 1777
The taxonomy of Least Weasel Mustela nivalis was reviewed by Abramov and Baryshnikov (2000), who considered Egpytian Weasel M. subpamata to be a distinct species, a treatment followed here. Tonkin Weasel M. tonkinensis and Sichuan Weasel M. russelliana, here treated as distinct species following Groves (2007), were included as part of M. nivalis by Abramov and Baryshnikov (2000) (and in previous versions of its Red List assessment). A weasel population found in Taiwan in the late 20th century and considered by its finders to be a new species allied to Stoat M. erminea is here considered, following Abramov (2006) to be part of M. nivalis.
Least Weasel has a circumboreal Holarctic distribution, taking in much of Europe, northern Asia and northern North America (Sheffield and King 1994, Abramov and Baryshnikov 2000). It is found almost throughout Europe, including on Britain (but not Ireland). In mainland Asia it ranges south to northern Mongolia (Bannikov 1954, Dulamtseren 1970), Korea (not just northernmost, where indicated by Won and Smith (1999), but also in southern parts; Abramov and Baryshnikov 2000), and northern China (Nei Mongol, Heilongjiang, Jilin, Liaoning, Hebei and Xinjiang provinces; Wang 2003). Populations further south are not here considered conspecific; see 'Taxonomic notes'. Further west in Asia it occurs south to Lebanon, Iran and Afghanistan (Abramov and Baryshnikov 2000, Habibi 2004). It is also found on Honshu, Hokkaido, Kunashiri and Etorofu islands in Japan (Abe et al. 2005), on Sakhalin and the Kuril islands in Russia (Abramov and Baryshnikov 2000), and on Taiwan (Abramov 2006). In North Africa it is confined to Morocco, Algeria and Tunisia; these populations have typically been considered native, but it is not impossible that they were introduced (Lebarbenchon et al. 2010). It has been introduced to many Mediterranean islands, the Azores Islands, Sao Tome off west Africa, and New Zealand (Sheffield and King 1994, Dobson 1998, Lebarbenchon et al. 2010). Statements that it occurs or occurred in Israel lack any credible basis (Werner 2012).
This species occurs from sea level up to at least 3,860 m.
In the European part of its range, there are documented population declines in some areas (e.g., Britain: Battersby 2005), and suspected declines in others. Although it has a wide distribution, it is considered rare in North America (Sheffield and King 1994). In Eurasia, it is relatively common, but not often seen (Sheffield and King 1994). Local densities of 0.2 to 1.0 individuals per hectare can occur in favoured habitats when prey are abundant (Sheffield and King 1994). However, over wider areas, the average density may be as low as one to seven per 100 hectares (Goszczynski 1977). Populations fluctuate both seasonally and annually, sometimes involving large increases of up to 10-fold, concurrently or within nine months of a population peak of small rodents, and lasting six to 18 months (Sheffield and King 1994). It is often thought to be rare (although sometimes locally fairly common) throughout its range in south-eastern U.S.A., but its actual status there is uncertain (Handley 1991).
Least Weasel tolerates a wide range of habitats, including forest, farmland and cultivated fields, grassy fields and meadows, riparian woodland, hedgerows, alpine meadows and forest, scrub, steppe, semi-desert, prairies, and coastal dunes (Sheffield and King 1994, Pulliainen 1999). 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 (Sheffield and King 1994). Food may be stored for the winter (Danzig 1992). Habitat selection is usually determined by local distribution of rodents. When foraging it avoids open spaces, where it is most vulnerable to predation by raptors (Sheffield and King 1994). It prefers dense, rank grassland where microtines (voles and lemmings) are abundant (R. McDonald pers. comm. 2006).
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