Weasel (genus Mustela)

Mammal Mustelid Small carnivore

Overview

Weasels are small, slender, fast-moving carnivores of the genus Mustela, within the weasel family (Mustelidae). The group includes the least weasel (Mustela nivalis), frequently described as the smallest carnivoran in the world. Despite their size, weasels are bold and effective hunters.

Their elongated, low-slung bodies are perfectly suited to following small prey into burrows and crevices, making weasels important predators of rodents across much of the Northern Hemisphere.

Conservation note: the least weasel and several relatives are widespread and generally not of conservation concern, though status varies among the many species in the genus. Verify specifics at iucnredlist.org.

Classification

Weasels are mustelids, related to stoats, polecats, ferrets, martens, otters, badgers, and the wolverine. The genus Mustela contains the true weasels along with several close relatives.

Habitat & Range

Weasels are found across much of Europe, Asia, North America, and parts of North Africa, in habitats ranging from farmland and grassland to woodland and scrub. They favour areas with plenty of cover and abundant small-mammal prey.

Diet & Hunting

Weasels are specialist hunters of small mammals, particularly mice and voles, using their slim bodies to pursue prey underground. They have a fast metabolism and must eat frequently relative to their size. They may also take birds, eggs, and other small animals when available.

Behavior & Adaptations

Weasels are mostly solitary, active by day or night, and constantly on the move. In colder regions, some weasels moult to a white winter coat for camouflage in snow, switching back to brown in warmer seasons. Their boldness and agility allow them to tackle prey close to their own size.

Appearance & Recognition

Weasels have a very long, thin body, short legs, a small flattened head, and a short tail. The least weasel is typically brown above and pale below, and is strikingly small. The elongated shape that lets weasels enter burrows is their most distinctive feature.

Human Interaction & Conservation

Weasels help control rodent populations and are mostly beneficial, though they occasionally take poultry or eggs. Most species are widespread; for any species of particular concern, and for regional context, consult authoritative sources.

More photos of the weasel