The weasel

Size and weight vary greatly and show clear sexual dimorphism, meaning that males and females differ. In the case of the weasel, this applies to size, with males being larger and heavier than females.

• Head-torso length: 11-26 cm
• Weight: 25-250 g
• Hibernation: no
• Pups per litter: 2-10 (several litters per year)
• Mating season: Peak in spring and summer, but possible almost year-round
• Life expectancy: 1-3 years, up to 10 years in captivity

The least weasel is the smallest representative of the mustelid family. The body is very slender and elongated with a brown upper side and white belly. The legs are short with brown paws. Only a few populations, especially those further north or in alpine locations, turn white similar to the related stoat.

Weasels can easily be confused with stoats. However, weasels are generally smaller, or only about half the size of stoats. The dividing line between the brown back and the light-colored belly is rather jagged and not sharply defined. The paws are brown. Those animals that turn white in winter never have a black tip on their tail. A brown spot in the corner of the mouth is also typical of the weasel.

Least weasels are predominantly diurnal and primarily go hunting at twilight and in the late afternoon. They live as solitary animals in fixed territories, the size of which can vary greatly depending on food availability. The boundaries of their territories are marked with scent marks and aggressively defended. Least weasels are very agile and inquisitive hunters, can climb very well and even swim. They are constantly exploring their surroundings. When hunting, they also penetrate into underground burrows and tunnels of their prey, making them highly successful hunters.

Least weasels occur throughout Europe (except Ireland, Iceland and the Arctic islands), in large parts of Asia and North Africa. In North America they are found in Alaska, Canada and the northern USA. The species was introduced to New Zealand, where it is considered invasive and poses a threat primarily to populations of ground-nesting birds such as kiwis or penguins.

They prefer richly structured fallow land, fields and meadow landscapes, pastures and forest edges. They can also become very common in extensive agricultural areas and near human settlements. Least weasels are extremely adaptable. For hunting or protection, they use rock crevices, hollow tree trunks or piles of stones just as much as the burrows of rodents and moles. Nests are often built in abandoned vole burrows, which are then lined with leaves and hair. The animals avoid deserts, deep forests and mountains over 3000 m.

Weasels are efficient hunters and pure carnivores whose diet consists mainly of mice. This makes them true food specialists. Their slender build enables these nimble hunters to penetrate the underground tunnels of mice. If necessary, they supplement their diet with birds, lizards, insects, worms, and even young rabbits. If the food supply is sufficient, they store it and eat it in several smaller portions throughout the day. Since weasels have a comparatively high basal metabolic rate, they need to eat about one-third of their body weight every day, which is equivalent to about five mice.

Due to their specialization in mice, weasels are bound to habitats with a minimum mouse density. They react strongly to vole gradations and follow the population fluctuations. In years with high mouse populations, there are also many more weasels; population lows are usually compensated for by several litters per year.

Natural enemies of the weasel include birds of prey, owls, foxes, and even the stoat.

The mating season for weasels begins early in the spring and lasts until late summer. However, if there is sufficient food available, the animals reproduce throughout the year and a female can give birth to two litters per year.

About 5 weeks after mating, 2 to 10 young are born in an underground nest, often built in old mouse burrows. The young are born hairless, blind, and toothless. After 2 weeks, they eat meat for the first time, and after about two months, they begin to hunt on their own. Raising the young is exclusively the responsibility of the female. During this time, she has to catch a particularly large amount of prey. A litter of 7 young, for example, requires 15 mice per day.

After 4-5 months, the young are sexually mature and the mother is ready to mate again. Premature young females from the first litter can then be mated themselves.

Since least weasels feed primarily on animals that humans consider pests, they are usually met with goodwill. Least weasels are classified as least concern (except in Switzerland, where the least weasel has been placed on the "Red List of Endangered Species"), but they are still protected year-round in many regions. They can only be hunted year-round in Burgenland, Lower Austria, and Vienna, while in Styria they are considered game animals, but have a closed season from February to June.

In richly structured habitats with sufficient food supplies, weasel populations remain stable. However, the loss of natural structures, intensification of agriculture, road traffic, and domestic cats are leading to a steady decline in numbers.

The long-standing connection between humans and least weasels is also evident in the various myths surrounding these animals. For instance, the hissing of a least weasel in England was considered a clear sign that the person was a witch. Alternatively, the least weasel itself was regarded as a transformed witch, which is why killing this animal would bring great misfortune.