Stoat (Mustela erminea): the short-tailed weasel and ermine

Physical characteristics

Stoats have a slender body, short legs, and a long neck that aid rapid movement through cover. Summer fur is typically brown above and pale below; in colder parts of their range they molt to an all-white winter pelt while retaining the black tail tip. Adults can reach body lengths approaching a foot, and their sharp dentition and flexible spine allow them to enter burrows and pursue prey. A commonly noted behavior is the way they deliver a killing bite at the connection between the skull and spine of prey, a precise technique used to subdue larger targets (see skull base).

Distribution and habitat

Stoats are broadly distributed across much of the Holarctic region, inhabiting a variety of environments from open grassland and farmland to woodland and tundra. They are adaptable and occur where small mammals such as rodents and rabbits are present. In some areas humans have introduced stoats outside their native range; these introductions have sometimes had serious effects on local wildlife communities.

Behavior and diet

Primarily solitary and territorial, stoats are daytime and crepuscular hunters. Their diet consists mainly of small mammals (mice, voles, rabbits in some regions), birds, eggs, and occasionally amphibians and insects. Stoats are capable of killing prey larger than themselves and will often cache surplus food for later consumption. They are agile climbers and can swim when necessary, allowing a wide range of hunting strategies.

Reproduction and lifecycle

Breeding in stoats can include a period of delayed implantation, a reproductive strategy seen in several mustelids whereby the embryo remains dormant for weeks or months before developing. This allows birth to occur at a favorable time of year. Litters vary in size, and young are raised in nests or burrows until they disperse. Juveniles mature quickly and establish territories of their own.

Human interactions, cultural notes, and conservation

Ermine pelts have a long cultural history and were prized for use in ceremonial robes and trim, symbolizing purity and status. Stoats have also been viewed variously as beneficial predators of pests and as harmful invaders when introduced to sensitive ecosystems; for example, introductions in island environments have led to declines in native bird populations. Conservation status of stoat populations varies regionally; some local populations face pressures from habitat change, persecution, or competition with introduced species. For comparisons with related species, note that the stoat is larger than the least weasel (weasel) and is distinct in its black-tipped tail and seasonal color change.

• Scientific name: Mustela erminea
• Common names: stoat, short-tailed weasel, ermine (winter)
• Diet: small mammals, birds, eggs; will cache food
• Notable traits: seasonal white coat in cold areas, black tail tip, ability to kill larger prey