In this month’s Gosforth Nature Reserve Journal, Christopher Wren, NHSN Naturalist, shares insights into Weasels and Stoats
Stoats and weasels are closely related small mustelids and have a lot of similarities but they are of different size, have different diets and occupy different ecological niches. Both are widespread but thinly distributed and are shy, fast moving and elusive so to see them is difficult (and lucky) and studying them is even harder.
Discussions of the differences in their appearance usually concentrate on the stoat’s longer, black-tipped tail and the dividing line between the brown and white fur (stoat – straight, weasel – wiggly) but perhaps most striking is the difference in size. A female weasel is tiny, weighing only 60g, about twice as much as a wood mouse. A male weasel is bigger, chunkier and weighs in at 120g. A female stoat is bigger again at around 250g and a male stoat is 350g, so weighing about six times as much as a female weasel. The photo below shows the four animals emerging from a camera box in roughly the same position. The photo is a bit blurry as it is a composite of heavily cropped screen grabs from trail camera videos but it shows the relative size of (from left to right) a male stoat, female stoat (unfortunately not paying attention), male weasel and female weasel.
Videos from inside the camera box gave the opportunity of making higher quality composite pictures (see below) to show the relative size of a female stoat (Left) and a female weasel (Right). The photos are from different days with different lighting conditions.
Here’s another example with the female stoat and a male weasel.
The first video shows a male and then a female stoat visiting (but unfortunately not entering) the camera box. I think the male must have left a scent mark in the entrance pipe as the female seemed distracted by it.
Both stoats and weasels will stand up to get a better look at their surroundings, as in this video of a stoat.
This wall was built specifically to attract small mustelids and is monitored by a trail camera. The female stoat was obviously very aware of the camera and disapproved of the invasion of her privacy.
Stoats rarely enter the camera box but weasels are much happier to go in and look around. The next video compares a male and a female weasel.
My last video shows a very persistent weasel hoping to find a dead mouse under the slate (there wasn’t one on this occasion).
Both stoats and weasels are very difficult for ecologists to survey as they have large territories with multiple nest sites and leave few if any field signs. Unlike mice, voles and shrews they are not amenable to live trapping but trail cameras are beginning to show some promise in seeing where they are and what they get up to.
You can get more updates on the local wildlife from Christopher Wren on his own TrogTrogBlog.