Mini Marvel

With a body weight of less than 125 g the weasel is our smallest carnivore, but what this diminutive predator lacks in size it more than makes up for in personality. Weasels are perhaps most commonly encountered when seen scurrying across a road or path, displaying the appearance of an elongated vole. The small size is even more apparent when you encounter a female; such is the degree of sexual size dimorphism that the smallest female may weigh barely a third of the largest male, the former measuring in at just 18 cm in length (4 cm of which is tail).

Small body size enables the weasel to target mice and voles within their burrow systems, a place where they are usually free from the risk of predation. Two-thirds of the weasel diet is made up of small mammals, making this a small mammal specialist, with a further quarter comprised of rabbits and the remainder a mix of other mammals, birds and their eggs and, occasionally, earthworms. Rabbits may be particularly important in spring, when young rabbits are widely available and small mammal populations tend to be at their nadir. Being smaller, the females tend to concentrate on small mammals, the male’s larger size allowing a wider range of prey to be taken.

The weasel has a reputation for being ferocious beyond its size and this is certainly not a species you would want to handle. I have caught weasels from time to time in live traps set for small mammals. While they usually rush off once released, I once had one face me down in a stand-off that last for several minutes; the weasel was decidedly nonplussed about having been shut in a trap for several hours. Such ferocity might explain why weasels may sometimes attack prey much larger than themselves. Rabbit has already been mentioned but to this species can be added common rat and even brown hare!

Weasels are easily overlooked beyond such chance encounters. In part this reflects their behaviour, with most of their activity centred on hunting under matted grass or within small mammal burrow systems. They seem less inquisitive than the larger stoat, to which they are related, but will investigate other feeding opportunities when favoured prey are less abundant. For instance, they are known to raid nest boxes erected for birds. At some sites, in certain years, weasels have been a significant cause of nestling mortality.

While small size may offer certain advantages, it does leave the weasel at risk of ending up on the menu for other, larger, predators, such as red fox and domestic cat. I’ve even found the odd weasel jawbone in a barn owl pellet, although it remains rather uncommon. 

Our smallest carnivore

A narrow blur of warm brown flashes across the road ahead of me. Low to the ground, like a vole that has been elongated, this tiny, cylindrical mass of energy is a Weasel. In an instant it is gone, a bounding leap takes it up into the verge and out of sight. This is typical of an encounter with our smallest carnivore, all too brief and wholly unsatisfactory. On those few occasions when I have come across dead Weasels, freshly killed by passing traffic, I have been surprised at just how small they are. Even the largest males only just reach 24 cm in length and weigh in at less than 200 g. More typically, the males weigh in at 125 g and the females 70 g.

The Weasel is to be found across most of England, Wales and Scotland but is missing from nearly all of our offshore islands and, importantly, Ireland. It does best where there are good numbers of its favoured small mammal prey (mice and voles) and is usually associated with the cover provided by hedgerows and old stone walls. Its small size, which opens it up to predation by larger predators, may be one reason why it tends to avoid more open habitats.

At this time of the year the males are extending their exclusive territories, presumably in an attempt to increase access to potential mates, which will result in a number of female territories being enclosed within the male’s wider range. Individual Weasels do not make their own dens but instead occupy those of other species (such as rats, mice and moles). The small body size is an adaptation, allowing the Weasel to hunt and pursue small mammal prey down into their tunnel systems. This small size also enables them to enter and raid bird boxes in times when small mammals are less abundant. They have also been reported to take young Rabbits (a not uncommon prey item for the larger males when young Rabbits are available), reptiles, amphibians and even earthworms.

Most young are born between May and July, remaining with the female for three months as an energetic family group, and an encounter with such a party can be an engaging experience. Weasels are naturally curious and it is possible to call them out from cover by imitating a squeaking sound like that sometimes uttered by their prey when in distress. Closer encounters sometimes occur when using live traps for small mammals. I have caught several over the years and will always remember the one that, on release from the trap, turned and berated me for several minutes before disappearing off into the undergrowth. What they lack in size they make up for in character.

Our smallest carnivore

A narrow blur of warm brown flashes across the road ahead of me. Low to the ground, like a vole that has been elongated, this tiny, cylindrical mass of energy is a Weasel. In an instant it is gone, a bounding leap takes it up into the verge and out of sight. This is typical of an encounter with our smallest carnivore, all too brief and wholly unsatisfactory. On those few occasions when I have come across dead Weasels, freshly killed by passing traffic, I have been surprised at just how small they are. Even the largest males only just reach 24 cm in length and weigh in at less than 200 g. More typically, the males weigh in at 125 g and the females 70 g.

The Weasel is to be found across most of England, Wales and Scotland but is missing from nearly all of our offshore islands and, importantly, Ireland. It does best where there are good numbers of its favoured small mammal prey (mice and voles) and is usually associated with the cover provided by hedgerows and old stone walls. Its small size, which opens it up to predation by larger predators, may be one reason why it tends to avoid more open habitats.

At this time of the year the males are extending their exclusive territories, presumably in an attempt to increase access to potential mates, which will result in a number of female territories being enclosed within the male’s wider range. Individual Weasels do not make their own dens but instead occupy those of other species (such as rats, mice and moles). The small body size is an adaptation, allowing the Weasel to hunt and pursue small mammal prey down into their tunnel systems. This small size also enables them to enter and raid bird boxes in times when small mammals are less abundant. They have also been reported to take young Rabbits (a not uncommon prey item for the larger males when young Rabbits are available), reptiles, amphibians and even earthworms.

Most young are born between May and July, remaining with the female for three months as an energetic family group, and an encounter with such a party can be an engaging experience. Weasels are naturally curious and it is possible to call them out from cover by imitating a squeaking sound like that sometimes uttered by their prey when in distress. Closer encounters sometimes occur when using live traps for small mammals. I have caught several over the years and will always remember the one that, on release from the trap, turned and berated me for several minutes before disappearing off into the undergrowth. What they lack in size they make up for in character.