Introducing the weasel. Mustela nivalis

Weasels belong to the Order Carnivore and the family Mustelidae which includes the Pine marten, Polecat, American mink and ferrets, which are all of a similar build in various degrees of size. The family also includes the Badger and the Otter. The weasel is placed in the genus Mustella {as are the stoats} and are given the specific name of nivalis. Nivalis alludes to snow and refers to the mammal turning white in snowbound regions of northern Europe. In Britain weasels do not change colour. Weasels do not occur in Ireland, however, the stoat does and is sometimes referred to as a weasle there!.


Description of the Weasel.

The Weasel.  Mustella nivalis.

Photograph courtesy of Snowmanradio at Creative commons attribution

The male weasel is about 21 cm long from nose to tip of tail. females 18 cm. males weigh about 120 gm and females 65 gm. The legs are short.

The body is long and slender  with fur that is chestnut brown on the back, the underparts are white, with small brown patches on the throat. The tail is relatively short and lacks the black tip which helps to differentiate it from the stoat. The colouring of this species remains the same throughout the year in Britain. An irregular line separates the brown coat from white chest and belly. No two weasels have the same exact patterning.

The ears are small and rounded. The eyes are dark and bright, enabling the creature to see well in the gloom of its victims burrows. Weasels are much smaller than the stoat and even a  large weasel could easily curl up in the palm of a mans hand. This diminutive size allows the weasel access to smaller holes and burrows than even a stoat can enter.

Lifestyle and breeding

Weasels tend to keep low to the ground and within cover in order to avoid predation. They are exceptional hunters and have a very inquisitive nature. They are closely related to the larger stoat and are just as efficient in the manner of dispatching their victims. However, the disadvantage for the weasel is that they can easily become the meal of the former, thus the weasel will avoid the stoat wherever possible. weasels also fall victim to many other predators such as the fox, cat and birds of prey particularly owls. Thus this small carnivore is ever alert and watchful.

Being smaller than the stoat it can gain access to burrows of the tiniest of mammals where they despatch the victim in the manner of the stoat, that is to say, by biting their prey at the base of the skull with poweful jaws and needle sharp teeth. The majority of victims are tracked downin this manner, however, the weasel is an excellent climber and will readily take eggs and nestlings located in trees, shrubs and general vegetation. There are records of hibernating dormice being taken from nest boxes by these wily creatures. When hunting in grassland they will momentarily sit on their haunches to smell the air, while at the same time scanning the surroundings for potential predators.

In common with the stoat,the weasel is rarely seen, and signs of their existence are equally difficult to detect. droppings known as scats are sometimes encountered, however, an experienced eye would be needed to -a, find them, and b, recognise them for what they are.

Weasels hunt in the main by their keen sense of smell and this readily takes them to carrion such as dead birds which provide an easy meal. To stay alive a weasel must eat throughout the day and night as food passes through the body in as little as three hours. Studies have revealed that if they were deprived of food for just a few hours they would be in danger of starving to death.  Scientific estimates reveal that a male must eat 33% of its body weight in 24 hours to avoid starvation.

Weasels inhabit mainy grassland, farmland and woodland. This is particularly true of rough grassland that are heavily populated by field voles, a favourite prey. Their frenetic lifestyle means that weasels only live for about 8-9 months.

Weasels, male and female, both live in separate territories and it is only in the spring that the males seek out females in order to breed. Breeding occurs throughout spring and summer. The pregnancy lasts for about 5 weeks with litters being born up until September.

They have just one litter per season as a rule but may produce another brood if food is plentiful. the brood consists of between 4-9 kits with 6 being the average. The kits are born naked and blind. The eyes open at the age of four weeks. They are capable of hunting and killing their own prey at the age of 8 weeks. They disperse at the age of 9-12 weeks.


This painting shows the stoat in its winter coat , note the black tip to the tail, and also the difference in size between it and the two weasels.

The stoat is a much larger mammal up to twice as big as the weasel.

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