Weasel

Weasels /ˈwiːzəlz/ are mammals of the genus Mustela of the family Mustelidae. The genus Mustela includes the least weasels, polecats, stoats, ferrets, and European mink. Members of this genus are small, active predators, with long and slender bodies and short legs. The family Mustelidae, or mustelids (which also includes badgers, otters, and wolverines), is often referred to as the "weasel family". In Great Britain, the term "weasel" usually refers to the smallest species, the least weasel (M. nivalis), the smallest carnivoran species.

Least weasels vary in length from 173 to 217 mm (6+3⁄4 to 8+1⁄2 in), females being smaller than the males, and usually have red or brown upper coats and white bellies; some populations of some species moult to a wholly white coat in winter. They have long, slender bodies, which enable them to follow their prey into burrows. Their tails may be from 34 to 52 mm (1+1⁄4 to 2 in) long.

Weasels feed on small mammals and have from time to time been considered vermin because some species took poultry from farms or rabbits from commercial warrens. They do, on the other hand, eat large numbers of rodents. Their range spans Europe, North America, much of Asia, and small areas in North Africa.

The English word "weasel" was originally applied to one species of the genus, the European form of the least weasel (Mustela nivalis). This usage is retained in British English, where the name is also extended to cover several other small species of the genus. However, in technical discourse and in American usage, the term "weasel" can refer to any member of the genus, the genus as a whole, and even to members of the related genus Neogale. Of the 16 extant species currently classified in the genus Mustela, 10 have "weasel" in their common names. Among those that do not are the three species of ermine, the polecats, the ferret, and the European mink.

The American mink and the extinct sea mink were commonly included in this genus as Mustela vison and Mustela macrodon, respectively, but in 1999 they were moved to the genus Neovison. In 2021, both Neovison species, along with the long-tailed weasel (Mustela frenata), Amazon weasel (Mustela africana) and Colombian weasel (Mustela felipei) were moved to the genus Neogale, as the clade containing these five species was found to be fully distinct from Mustela.

The genus name Mustela comes from the Latin word for weasel combining the words mus meaning "mouse" and telum meaning "javelin" for its long body.

The following information is according to the Integrated Taxonomic Information System and MammalDiversity.

¹ Europe and Northern Asia division excludes China.