What is a weasel?
What is the difference between a weasel, stoat, ferret or mink?
As it turns out there is no easy answer to this question. In fact, you could probably write a pretty lengthy essay on how these words are used and what species they refer to.
But I am still going to try to answer the question, so if you're curious, buckle up for the ride.
Terms we will be going over:
Marten
Sable
Fisher
Mink
Polecat
Ferret
Stoat
Ermine
Weasel
All of these words refer to members of the family Mustelidae, which includes weasels, otters, badgers, and wolverines.
All of these animals have a similar shape: long body, short legs, small round ears
Now let's talk about what each of these words means and what species they refer to
Marten
Image Source
Marten refers to a specific genus of mustelids that live in North America, Europe, and Asia. There are eight species. They tend to be larger than most of the other animals we're talking about here, with fluffy tails
They are semi-arboreal species who are skilled at climbing trees
Sable
Image Source
A Sable is a specific species of marten native to Russia.
Fisher
Image Source
Fishers, also called fisher cats, are a species closely related to martens and wolverines. They are arboreal like martens, but are bigger and live only in North America, mostly in Canada and the far north of the United States.
Mink
Image Source
Mink refers to two separate species: the American Mink and the European Mink. Despite sharing a name, they are not each other's closest relatives.
They do look almost identical. They are dark brown with a small white patch on the throat/face and small ears. Behaviorally they are similar to otters, spending most of their time near water and eating fish. You won't mistake them for an otter though, they are much smaller.
Polecat
Image Source
In my own experience, when people say polecat they are usually referring to the animal pictured above, the European Polecat.
They have a unique color pattern featuring the distinctive mask. They are bigger than most things called weasels, but are smaller than martens.
Image Source
However, there are several other species referred to as polecats. The European Polecat's most closely related species are the Steppe Polecat and the American Polecat (more commonly called the Black-Footed Ferret).
Another mustelid family, Ictonychinae, has several members referred to as polecats. The Marbled Polecat, the Striped Polecat, and the Saharan Striped Polecat.
Image Source 1, Image Source 2
Ferret
Image Source
Two species are referred to as ferrets. The Domestic Ferret and the Black-Footed Ferret (pictured above). The Domestic Ferret is descended from the European Polecat.
Stoat, Weasel, Ermine
Now things get more confusing. What the words "stoat" or "weasel" or "ermine" means depends on where you live.
Image Source
If you live in Europe then this is what you refer to as a stoat. It is a specific species.
Somewhat confusingly, this is also an ermine: but only in winter, when it has its white coat.
Image Source
A weasel would refer to this animal:
Image Source
This is the Least Weasel, also called the Common Weasel. They are tiny creatures, smaller than a stoat, with no black tuft at the end of their tail.
Both of these species also live in North America. However, the names we use are much less specific in the US. You might call what Europeans call a stoat a stoat as well, but I have usually heard it referred to as the Short-Tailed Weasel.
The Short-Tailed Weasel is probably called that in reference to the Long-Tailed Weasel, which is a species specific to the Americas. It is larger than the Short-Tailed Weasel with a longer tail and tends to live further south, though their ranges overlap.
Image Source
To make things more confusing, the Long-Tailed Weasel can also be called the Big Stoat, or the Masked Ermine.
There is also an entirely separate species which is called either the American Ermine or the American Stoat. They are pretty much identical to the Short-Tailed Weasel but have recently been identified as being a separate species. I would guess that they are probably also called the Short-Tailed Weasel pretty often.
But at least there's the Least Weasel right? That one's definitely a weasel. Except that I've heard people call this one a stoat too!
Basically, I don't think US Americans have any idea what the difference is between a weasel, a stoat, or an ermine. Personally, I have given up trying. I just call them all weasels.
Meanwhile, around the world, there are a huge variety of other mustelid species which are called weasels. At least in English. Most of these species have their own names in the native language to their area. But English speakers call them weasels. Not stoats or ermines*. Those names seem to be reserved for European and North American species.
*There is one other species called an ermine, the Haida Ermine, which lives on a few islands off the coast of North America
Here's a few weasels, just to give you a taste:
From left to right: Malayan Weasel, Mountain Weasel, African Striped Weasel, Japanese Weasel, Patagonian Weasel
So what is a weasel? It depends on where you live! However, it is also clear that "weasel" has become a rather general term to refer to Mustelids of this particular shape. There is in fact really no reason that any of the animals on this list couldn't be referred to as a type of weasel. Based on the phylogenetic tree, otters are also probably weasels. Possibly badgers as well.
This is the approach I've taken. It's all weasels. Everything's a weasel. Because if I spend any more time thinking about this I will lose my mind.
