Species: Mustela nivalis (European Weasel)
IUCN Status: Least Concern
Population trend: stable
Distribution: throughout England, Scotland and Wales but absent from Ireland, the Isle of Man and most smaller islands. Found widely in rest of Europe and in much of Asia, North Africa and parts of the United States. Introduced to New Zealand.
Habitat: woodland, hedgerows, farmland, moorland and mountains.
Description: long, slim; short furry tail. Reddish-brown upperparts separated from white underparts by a wavy flank line.
Length: male - head & body
21.5cm - 28.5cm. Female is smaller.
Height: to shoulder, 4 - 6cm.
Weight: males, up to 115g. Females, up to 59g.
Life-span: 1 - 2 years in the wild. Up to 10 years in captivity.
Food: mainly mice and voles but also rats, moles, small birds, birds' eggs, rabbits.
The weasel is Britain's smallest carnivore and belongs to the same family as the stoat and otter. It is a fierce hunter and is usually only spotted as a long, thin tan-coloured streak as it dashes across a road or woodland path.
Each weasel has a territory of 10 - 20 acres (2.5 acres = 2 football pitches). Males' territories are larger than females' and they may overlap with one another. The size of the territory depends on the food supply; where there is plenty there is no need to hunt for food far and wide. The individual territories are marked with strong-smelling secretions from the anal scent glands. Females stay in their territory throughout the year, but during the mating season, males may travel long distances outside their normal range to find a mate. Weasels do not make themselves any kind of permanent burrow - they usually use the tunnel or burrow of one of the animals they have eaten!
A weasel hunts mainly by scent and investigates every likely hole and crevice it comes across. It is small enough to follow its favourite prey - voles and mice - down into their underground runs. The victim is killed with a sharp bite to the back of the neck. Prey is usually taken on the ground, but weasels can climb well and sometimes raid a bird's nest box. Weasels are good swimmers too and will chase water voles through the water.
Hunting is done mainly at night, although weasels often hunt during the day too. The favourite food is the field vole and when voles are plentiful there will be a high weasel population. Vole populations fluctuate and when they are low, the weasels do not breed and their populations decrease in turn.
A weasel eats about 28g of food a day - about 25% of its own body weight.
Weasels mate in the spring and this is the only time males and females associate with each other. After a 5 week gestation period (the time between mating and birth) a litter of 3 - 8 babies (kittens) is born, in April or May. There may be a second litter in July or August. The kittens are born in a nest of leaves or grass in a hole or crevice. Their eyes open when they are about three weeks old and they are weaned at 4 - 5 weeks. The family often goes out hunting together until the youngsters can kill for themselves at 8 weeks. At 12 weeks the mother drives her offspring away to find territories of their own. Young weasels, born early in the year, are capable of breeding themselves during their first summer, unlike other British carnivores which do not breed until their second year.
Weasels and Humans
Weasels are often known as sneaky and deceitful creatures. We even associate the name “weasel,” with negative behaviours and weasels often represent dishonest characters in books. Humans have persecuted weasels over the years particularly in areas where pheasants and partridges are reared; gamekeepers and farmers have always regarded weasels as vermin and trapped them in large numbers. In fact, since one weasel may eat hundreds of mice in a year, it should be looked on as a useful friend, doing more good than harm!
Cats, owls, foxes and birds of prey will all try to kill weasels, although a weasel will fight hard to defend itself. Many weasels are killed on the roads too, but despite the dangers they face from humans, they are still quite common and are under no threat as a species.