Weasels are mammals of the genus Mustela, family Mustelidae, which is often aptly referred to as the “weasel family”. In the United Kingdom, the word “weasel” will often refer solely to the smallest species of weasels, the least weasel (Mustela nivalis). There are 17 known species of weasels, the most widespread of which is the common weasel (also known as the European weasel, the least weasel, and, scientifically, as Mustela nivalis).
Description and distribution
Weasels have long, slim bodies, short legs, a small, narrow head (which is almost the same thickness as the neck), and a flexible spine, appearance and anatomy that makes it easy to crawl and manoeuvre in tight spaces. A weasel’s head is triangular; they have a pointed snout, small, rounded years, and black, beady eyes. The teeth are sharp and pointed, like a canine’s. On their paws, weasels have five toes, tipped with small, non-retractable claws.
Depending on the species, length can vary, ranging from 17,3 to 21,7cm. A weasel’s tail can measure between 3,4 to 5,2cm. Weight can go up to 170g. Weasels are the smallest carnivorous animals in the world, with females being generally about a quarter smaller (as well as lighter) than males. Colouring also varies, although most weasels will have a red or brown upper coat and white bellies. Some individuals will change from brown to white in the winter, so they are camouflaged in the snow.
Weasels can be found on all continents, except Antarctica and Australia (and surrounding islands). Habitats vary, weasels living in woodlands, coniferous forests, and grassy plains; more and more often now, weasels can also be found in urban areas, especially close to farms, where food is easily available. They enjoy living in places where there is plenty of water and vegetation to hide in.
They are solitary, territorial animals, and spend most of their time hunting, which they do both during the day and night. The fact that a weasel’s body is small and thin means that it is perfectly adapted for hunting, but also that there is a large body surface to body weight ratio; only a thin layer of fat covers its body, which causes it to easily lose heat. This is one of the reasons why weasels need to be constantly moving and hunting.
Breeding and dietary information
The only time when weasels tolerate one another is when they need to mate, which happens once or twice a year. Following this, there comes a gestation period of around 5 weeks. The female gives birth to 1-10 kittens. Weasels build nests in crevices (such as tree roots) or in old mouse or vole burrows, lining them with grass, moss, hay, and fur; this is where the younglings spend the first weeks of life. They grow very quickly, though, weaned and able to hunt small prey by the time they are only two months old. They then leave their mothers in search of their own territory, becoming completely independent around the age of 3-4 months. Females are able to mate by the time they are 2 years old. The general lifespan of a weasel is 3 years, with males living significantly less (sometimes not even reaching a first birthday), seeing as their tendency to roam longer distances in order to find a mating partner exposes them to danger in the form of numerous predators. These predators include birds of prey (such as owls, hawks, eagles, etc.), which are the most common; foxes and snakes also hunt weasels, along with some domestic cats and dogs.
When it comes to their dietary needs, weasels eat small mammals, most commonly mice, voles, shrews, lemmings, but occasionally also birds, snakes, various other small reptiles, and insects. They have also been known to consume eggs. Although they are relatively small and may seem harmless, weasels are very good and very active predators. One of the reasons why is because they have very fast metabolisms and need to eat around half of their body weight every day. As a result, a weasel’s bloodlust is instinctual, with them killing anything that moves and seems to be prey, even on a full stomach. They hunt by cornering their prey, wrapping their long, muscular bodies around it in order to immobilize it, and then killing it by biting the back of its head, puncturing its skull or its spinal cord. The only other animal with the same hunting pattern is the jaguar. They can kill animals that are up to 10 times larger (ducks, rabbits, etc.), and, if they cannot consume them in a single sitting, they will hide the leftovers in small underground holes. Therefore, in the winter, if they deem it too cold to step outside of their den, weasels can just eat whatever they have in the “fridge”.
Weasels as pests
Because of the weasels’ diet, they have been known to eat eggs, poultry, and rabbits from farms. From this point of view, one can understand why they are sometimes considered to be pests. Moreover, a concern that is always present when there is wildlife around your house, weasels can carry diseases (such as rabies), their faeces posing threats to both pets and children. If cornered, weasels can also become aggressive, biting people, which brings concerns, once again, when it comes to the possible diseases they may carry. On the other hand, they also eat large number of rodents, which are pests themselves.
As is the case with many animals, weasels have been assigned a variety of cultural meanings. In Greece, they are considered to be a sign of evil if they are found inside or in the vicinity of a house. In North America, as well, Native Americans thought the same, claiming that crossing a weasel’s path guaranteed a “speedy death”. In English (the language), the word “weasel” can be used to refer to someone who is “sneaky”, “conniving”, or “untrustworthy”. In Macedonia, on the other hand, they are considered to be an omen of good fortune.
When it comes to their activity around your farm, weasels do not only feed on chickens or their eggs, but they can also cause a lot of distress around your flock. Their very presence can disrupt normally active laying hens and cause them not to lay eggs for fear of danger. They will get in feed bins and can cause the spread of disease among creating a terrible mess. Due to their strength, tenacity and small size, weasels are quite unique amongst farm predators. By securing your chicken coop, keeping it clean and locking up your free-ranging chickens at dusk, you will have a chance of protecting them against these predators. For more preventive measures against weasels, you can check our relevant article on how to ‘Prevent infestation with Weasels’. If you are already dealing with an infestation and your aim is to eliminate them from your property, you can check our article about ‘How to get rid of Weasels’ and learn about the various methods of control that you can use.