Head to head
Least Weasel vs Stoat
The weasel and the stoat are close relatives and look very similar, both long, thin, short-legged predators with a brown back and a cream belly that hunt mice and voles across the Northern Hemisphere. In Britain and much of Europe they are the two small mustelids people are most likely to glimpse, and telling them apart comes down to a few reliable features.
| Least Weasel | Stoat | |
|---|---|---|
| Size | Smaller; males about 25 cm, the smallest carnivore | Larger; males about 30 to 40 cm |
| Tail | Short, entirely brown | Longer, with a bold black tip year-round |
| Brown and white border | A straight, slightly wavy edge | A sharp, clean line |
| Gait | Low bounds close to the ground | Higher, arch-backed bounds |
| Main prey | Mice, voles, and shrews | Voles, mice, and rabbits |
| Winter coat | Turns fully white in the north | Turns white but keeps the black tail tip |
| Winter name | Just a weasel | Ermine |
| Memory aid | A weasel is weaselly recognised | A stoat is stoatally different (black tail tip) |
Weasel vs Stoat: common questions
What is the single best way to tell a weasel from a stoat?
The tail tip. A stoat has a distinct black tuft at the end of its tail in every season, and it is obvious even at a distance and even in winter when the rest of the animal has gone white. A weasel has a short tail that is brown all the way to the end, with no black. Backing that up, a stoat is clearly larger and longer-tailed overall, and the line where its brown upper parts meet its white under parts is crisp and straight, while on a weasel that line is more broken and wavy. The old rhyme, that a weasel is weaselly recognised while a stoat is stoatally different, is a reminder that the stoat is the one with the extra feature, the black tail tip.
Are weasels and stoats the same animal at different ages?
No. They are two separate species, Mustela nivalis and Mustela erminea, and a weasel does not grow into a stoat. A full-grown weasel stays much smaller than a stoat, and it never develops the black tail tip. The confusion is understandable because a large male weasel and a small female stoat can be closer in size than a small female weasel and a large male stoat, and both species have the same colours and body shape. But the black-tipped tail is present on a stoat from an early age and absent on a weasel throughout life, so it separates them regardless of size or age.
Why did stoats and weasels cause such damage in New Zealand?
New Zealand evolved with no native land mammals apart from bats, so its birds developed for millions of years with no defence against fast, agile mammalian hunters, and many became flightless or ground-nesting. Stoats and weasels, along with ferrets, were deliberately introduced in the 1880s in a misguided attempt to control rabbits, which were themselves an introduced pest. The mustelids largely ignored the rabbits in favour of easier prey and spread rapidly, and they now kill huge numbers of kiwi chicks, mohua, kaka, and many other native birds, as well as lizards and large insects. Stoats in particular are considered the single biggest threat to kiwi survival on the mainland, and intensive trapping and, in places, aerial control are used to protect the most vulnerable populations.