Least Weasel

## Description

The least weasel (Mustela nivalis ), little weasel, common weasel, or simply weasel is the smallest member of the genus Mustela, family Mustelidae and order Carnivora. It is native to Eurasia, North America and North Africa, and has been introduced to New Zealand, Malta, Crete, the Azores, and São Tomé. It is classified as least concern by the IUCN, due to its wide distribution and large population throughout the Northern Hemisphere.

The least weasel varies greatly in size over its range. The body is slender and elongated, and the legs and tail are relatively short. The colour varies geographically, as does the pelage type and length of tail. The dorsal surface, flanks, limbs and tail of the animal are usually some shade of brown while the underparts are white. The line delineating the boundary between the two colours is usually straight. At high altitudes and in the northern part of its range, the coat becomes pure white in winter. Eighteen subspecies are recognised.

Small rodents form the largest part of the least weasel's diet, but it also kills and eats rabbits, other mammals, and occasionally birds, birds' eggs, fish and frogs. Males mark their territories with olfactory signals and have exclusive home ranges which may intersect with or include several female ranges. Least weasels use pre-existing holes to sleep, store food and raise their young. Breeding takes place in the spring and summer, and there is a single litter of about six kits which are reared exclusively by the female. Due to its small size and fierce nature, the least weasel plays an important part in the mythology and legend of various cultures.

## Appearance

The Least weasel lives deep in the Northeast Asian deciduous forest. It hunts day and night, aided by its sharp nails and long slender body. It is the world’s smallest carnivore. According to Blackfoot legend, this species is the bravest of all animals, a hunter that is bold out of proportion to its size. Modern scientists agree with this view, as every single feature of these graceful, lightning-fast little animals appears to be designed so that they are the perfect predator.

## Distribution

The Least weasel has a Holarctic circumboreal distribution, including much of North Africa and Europe, Asia, and regions of northern North America. Round in a variety of habitats, this animal favors plentiful prey and good cover, including woodland, grassland, mountains, sand dunes, urban areas, moors, and marshes.

## Behavior

Except for the breeding season, the Least weasels are solitary. They are territorial animals and form gender-based dominance hierarchies, with older males being dominant over juvenile males and females. Least weasels need to eat very regularly so that they do not starve to death, and often they are found foraging at any time of day. They commonly use food caching, as they often kill prey bigger than themselves, but only consume a few grams of meat for each meal. Caches are hidden around the den entrance, and latrine sites are as well. An individual scent marks around a den site with secretions from its anal glands. When startled or cornered, these glands release a bad-smelling fluid that will deter an antagonist. Least weasels also sometimes perform a “weasel war dance”, consisting of a series of twists and leaps, often accompanied by noises like barks, an arched back, stiff limbs, and erection of their caudal and dorsal hairs. Weasels of any age perform the dance, though it is more common in the younger ones, especially kits when playing with their siblings.

## Diet

Least weasels are predominantly carnivores, they mostly eat small rodents like mice and voles but also eat frogs, fish, birds’ eggs, lizards, salamanders, and carrion.

## Reproduction

The least weasels are polygynandrous (promiscuous), with males and females mating numerous times with many partners. Males defend territories, usually against other males, but in the breeding season, they leave their territories to search for females. The breeding season is from March to June (though breeding can occur year-round). Following gestation of 34-37 days, a litter of 4-6 kits is born. Young are weaned at 4 weeks old and at 8 weeks old they are able to hunt, often going with their mother and hunting in 'gangs’. They are independent when they are 9-12 weeks of age and reach reproductive maturity when they are 3 to 4 months old.

## Population

### Population threats

Threats to this species include simplification and habitat loss. Agricultural changes in many areas have led to the reduction or loss of rough grasslands, prime habitat for Field voles, which is a primary source of food for this species. They are rarely seen and so are considered relatively rare. Population numbers vary with the abundance of prey, and they themselves are vulnerable to a range of predators, such as domestic dogs, cats, and foxes.

### Population number

The Least weasel has a wide distribution and presumed large population, but no estimate of population size is available for this species. Currently, the Least weasel is classified as Least Concern (LC) and their numbers today remain stable.

### Ecological niche

Least weasels, being highly-skilled predators of rodents, play a vital role in initiating or maintaining cycles in rodent populations, an important part of the tundra ecosystem, where specialized predators, like Least weasels, play a role to keep lemming populations in check. In New Zealand, on the contrary, where the Least weasels have been introduced, bird species are negatively affected by predation by this species, especially Brown kiwis, which live on the ground.

## Fun Facts for Kids

Weasels seem to be almost boneless, being so flexible they are able to reverse directions in what seem to be impossibly small spaces.

Weasels have short, heavily muscled jaws, with 34 extremely sharp teeth.

Historically, weasels were considered to have magical powers, able to bring their dead offspring back to life, and able to hypnotize their prey by dancing. This 'dancing' behavior, in fact, is believed to be a response to the discomfort of internal parasites.

Every day weasels can eat more than 50% of their body weight, more in the winter months.

Least weasels and stoats look very alike but can be told apart by the stoat’s tail having a black tip.

Under ultraviolet light, the white winter coat of this animal glows a bright lavender.

As weasels have a high ratio of surface area to weight, in winter they conserve body heat by curling up into a ball and slowing their metabolism.