Ferret family tree: Mustelidae


Last week we looked at the taxonomy, the classifications system, and we narrowed it down to where we want to be, which is in the caniform, in the carnivora area of the animal kingdom.

This week we’ll look at the family mustelidae, particularly at the genus mustela.

Now mustela actually means weasel and for a lot of other countries outside the United Kingdom, the term weasel is actually an overarching term for anything of our little ferrity weasily type animal.

In the UK, when you say weasel, we are thinking of a specific species which is weasel. So actually what we Brits think of as a weasel is a specific species, called the least weasel, the little weasel or the common weasel. That is mustela nivalis. So Mustela is the the genus and nivalis is the species.


Weasels are the smallest of the weasel family. They are super tiny, but they’re also super fierce. Sadly they do get the bad guy reputation and quite often they are the bad guys in cartoons. But I think it is only because they’re super clever and super fierce. For all they’re small and cute, you wouldn’t want to handle them because you wouldn’t get your fingers back.

They have that typical elongated body and quite short legs on the whole. There are exceptions but generally this is standard for this kind of creature. The tail length relative to the size of the body, can often change. So for weasels, they generally have a shorter tail. They are brown with a white belly. The line demarcating the brown, and then the white of the belly is generally wavy on a weasel. And that’s one of the ways, certainly in the UK, that you can tell the difference between a stoat and a weasel.

One’s weasley recognisable and the other’s stotally different!


A bit like the stoat in higher altitudes and in more northern parts of the world common weasels can actually be pure white. We don’t get that in the UK as much.

There are 18 different subspecies of weasel. The males like to mark their territory and they do that using scent. Weasels eat a lot of small rodents and rabbits. When you look at the size of a weasel compared to the size of the rabbit, you can see why they get a reputation as fierce. They’re wonderful creatures. And you’ll see them quite often on back lanes, scuttling along and they’re
probably not much bigger than a rat.


A stoat’s genus is still mustela and its species is erminia because the stoat can also be called an ermin because they go pure white in the winter. And for those lucky few who have seen it, that does happen in the UK.

One of the great ways you can tell the difference between a stoat and a weasel is that the stoat has the black tip on the tail. Again, I’m talking about in the UK. I can’t talk about every single different type of stoat because there are 35 different subspecies of stoat.

In the UK stoats are ever so slightly longer and the tail relative to the body is longer. It always exceeds one third of the entire body length. If you see something small and brown and the tail seems quite stumpy and less than one third of the body length, it’s probably just a geet big weasel.

Stoats have a prolonged gestation period. Between mating and actual birth, they can almost put everything on pause to give birth at a time when the seasons are are more positive for that little baby to be born into. You can have up to a 10 month gestation period for the stoat. And you can also get between three and 13 young.

While weasels tend to eat more rodents and rabbits, stoats tend to eat more birds, eggs, frogs and other invertebrates. Weasels fight and kill above their weight while the stoats tend to hunt within their own weight bracket.


The Eurasian, EU or Russian Mink are still part of the mustela genus which makes them closer to the stoats, the weasels, the polecats that we’ve looked at. And of course our own darling ferrets. While the American mink is actually a different genus – neogale, making it a totally different genus. That is why we tend to class our EU minks in with our polecats and our ferrets.

The mink is semi-aquatic. It likes to hang around water a lot. It actually has webbing between its feet which will help it in the water. It can actually hold its breath underwater for up to two minutes. And it will mainly be found around water bodies, which won’t freeze in the winter, for that reason.

The mink is critically endangered now. There’s been a decline of over 50% just in the last three generations, partly to do with climate and habitat change. Climate change has created changes in the habitat, which has been part of the issue. But habitat changes due to buildings and other man-made interactions.

So some of the river ecosystems that have been changed and are destroyed has had a massive impact on the mink population, as has the introduction of the American mink.

Because it’s part of the mustela group, the mink has an elongated body and short limbs. So again, it’s a bit more like ferrets and polecats. It’s a bit more solid.

Mink have short tails like the weasel but are much bigger than weasels. They are a dark brown or a reddish brown. Certainly in the winter they are more dark brown rather than a lighter brown. And in the summer some red comes through.

The different between EU and American mink is that the European mink will always have a little bit of white on the top part of its lip, and the rest of it will be pretty much black with a small amount of a mask on the top and the bottom. The American mink will only ever have white on the bottom part of that lip on its bottom jaw.

Mink can be albino as well. There is the possibility of albinoism, a bit like with ferrets. Albinoism is more common in ferrets than in the human population.

They like to burrow in small holes and only have a small territory, especially in the summer. I think that’s because they don’t need to go far because everything that they need is where they are. They will mainly eat voles, crustaceans, frogs, fish and water insects. Once again, they are similar to the stoats and weasels in terms of size.

Mink are much more water-based animals and they, just like stoats and weasels, are susceptible to being prey, mainly by the red fox, some larger owls and the golden eagle.

Check out the video to go with this blog.

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