There is a saying that ‘a weasel is weasel-ey recognised and a stoat is stoat-ally different’, but it only serves to confirm how difficult it is to tell the two species apart.
These little brown mustelids are both fast and ferocious, with sinuous bodies and short legs. But there are a few key indicators to look for if you see a tiny, slim brown mammal slip through the undergrowth at speed.
Black tip to the tail: The most important of these is that stoat’s tails have a bristly black tip whereas the weasel’s tail is much shorter and light brown all the way to its tip.
Look at the line where belly meets back: On a stoat there is a clean, straight line where the cream fur of her belly meets the brown fur of her back. On a weasel, it is very jagged. If you get close enough to these animals in the wild to see this line, it is a good way of telling weasels and stoats apart.
Size matters: Stoats are always bigger than weasels. In simple terms, think of a weasel as a long sausage, whereas a stoat is more like a cucumber. There is quite a difference between the males and females of each species. A female weasel is truly tiny weighing just 65g whilst a male stoat is just over five and a half times heavier at 360g.
White in winter: Stoats are the only one of the two that has the ability to turn white in winter. Although not all stoats turn white, it’s down to genetics – so just because it is winter don’t dismiss a brown-furred stoat as a weasel, use the guidelines above.
In Latin: The Latin name for the weasel family is Mustela. In the UK the sub-species, 'mustela nivalis, is known as weasel. In the US, the same animal is called a least weasel. Meanwhile the Latin name for the animal known in the UK as a stoat and in the US as a short-tailed weasel, is 'mustela erminea', a reference to the fact that a stoat is able to turn white, or ermine, in winter.
Read more:
Stoats & Weasels - Much maligned in History
Mustelids and Me: The wonderful world of Weasels and Stoats as featured in BBC Countryfile Magazine June 2018
Watch my weasel and stoat videos on Youtube
6 comments
Very helpful thank you. The name changes are complicated when you are British
There are in fact three species of weasels in North America that turn white in winter.
Least weasel (weasel in Britain)
Short-tailed weasel (stoat in Britain)
Long-tailed weasel (does not live in Britain)
Long-tailed weasels are difficult to distinguish from stoats, especially in the winter, since they look very much alike. The long-tailed weasel has a somewhat longer tail, and is larger.
In summer, the long-tail has a creamy yellowish tummy, while the stoat is more just white. Some, but not all, of them have a splash of white white fur on their forehead and sometimes in front of the ears.
In their winter coat, they can be very difficult to tell apart. They’re both white with black tail tips, and although the long-tailed weasel does have a longer tail, this varies per individual, and the fluffy winter fur can mislead the eye into thinking it looks like a stoat tail. There is considerable overlap in the size of the two species, with a female long-tailed weasel being about the size of a male stoat, so this isn’t reliable either. They have subtly different head shape, with the long-tailed weasel’s head being slightly more pointy and marten-like, but again, it’s very slight.
Despite looking very similar, stoats and long-tailed weasels are only distantly related, with the long-tailed weasel actually being related to the American mink.
Anyway, my feeling is that Britain just doesn’t get enough snow for white winter coats to be useful. Weasels have lost them entirely, and stoats only rarely have them.
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Just a quibble, but there are two species of weasels in North America that do turn white in the winter, the long-tailed weasel and the least weasel. In the northern part of its range and at high altitudes, the least weasel (which is termed weasel in England), changes colour in the winter, the coat becoming pure white and exhibiting a few black hairs in rare circumstances.
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