The weasel

David Chapman / 30 November 2018

Wildlife expert David Chapman introduces the weasel, the tiny carnivore with a big personality.



There are many examples of animals’ names that have weaselled their way into the English language, usually due to some unusual physical characteristic or behavioural trait, and the weasel has both.

The thin, sharp face of a weasel is responsible for the term ‘weasel-faced’ and the same profile is responsible for the naming of the weasel’s-snout, a rare arable flower, also known as the lesser snapdragon. Recently the term ‘weaseling’ is being used for an outdoor activity which combines rock-hopping and scrambling between boulders. The connection here is the way in which people pop-up from between boulders as part of their activity, not unlike the way in which a weasel might appear from a hole or behind a rock.

Generally though, the verb ‘to weasel’ means to achieve something by cunning or deceit which is a reference to the way in which weasels and stoats can mesmerise their prey before striking. The movement of weasels can be confusingly fast and seemingly random, so much so that one of the collective nouns for weasels is a ‘confusion’.

In fact it would be very rare to see more than one weasel at a time except possibly a group of kits. But the myth that gangs of weasels hunt together has been reinforced through children’s literature such as in ‘The Wind in the Willows’.

The weasel in the UK

The weasel is Britain’s smallest terrestrial carnivore, and it is astonishingly small. Adult females may only be seventeen centimetres long, males are slightly longer typically up to twenty-two centimetres long, and that includes their tail. In a sense this measurement gives a misleadingly large impression of their size. An adult female weasel can weigh only sixty grams, that’s less than the weight of three AA batteries. It is their diminutive girth which makes them look tiny and enables them to hunt mice and voles by entering their tunnels.

Weasels don’t hibernate and need to eat a third of their body weight every day of the year. Their prey is dominated by mice and voles, though they will also take small rabbits and rats as well as the eggs and young from birds’ nests, which has brought them into conflict with humans.

Breeding habits of weasels

Male weasels do their best to defend a large territory which might be twenty hectares and within that area might be the territories of several females but the two don’t associate with each other until it is time to breed. Unlike other mustelids, female weasels cannot delay the implantation of the egg in the womb so as soon they are mated they become pregnant. For this reason, when prey numbers are high they can respond quickly and produce a greater number of young, sometimes having two litters in a summer.

A female weasel will often make a nest in an old rodent tunnel, a hole in a wall or some similar-sized space. She gives birth to between four and six young kits which are weaned by the time they are eight weeks old and soon after that become independent. Young weasels can breed in their first summer, making them unique amongst British mustelids, but their lives are typically very short with only 10% making it to their second birthday.

Where to spot weasels

Weasels occur in a wide range of habitats including woods, moors, gardens, farmland and hedgerows depending mostly on the availability of suitable prey. They themselves can fall prey to a wide range of other creatures including foxes, birds of prey and cats. Many are killed on our roads and many more are killed by people who wish to protect their interests, particularly on grouse moors. There are times when a weasel might be taken by stoat since the stoat is the larger of these two very similar animals.

The difference between stoats and weasels

Both the stoat and the weasel are brown on top and creamy-white underneath. They are both very long and thin and though the stoat is the larger of the two it isn’t always easy to distinguish them on size alone when they move so quickly! In relation to its body the stoat has a longer tail than the weasel and the tail tip is black. By contrast the weasel has a much shorter tail which is all brown.

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