Weasel, ermine, stoat, or mink?

Updated: Feb 16

This is a question that I often get in one form or another, especially in regard to trail camera photos taken during our Carnivore Camera Survey. Before I get to the main question, I really need to talk a bit about mustelids in general. The weasel family, Mustelidae, is an amazing and diverse family. Its largest member is the ferocious wolverine weighing in at about 40 lbs. Interestingly, the smallest carnivore in the world, the tiny least weasel, also belongs to this family, with males topping out at about 8.8 ounces and females at 4 ounces (yes, there is a large sexual dimorphism in weasels, that is, males are substantially larger than females in many species). Not only is the family diverse in size, but it is also diverse in the habitat they occupy. Most species are terrestrial; however, the family includes both semi-aquatic and aquatic freshwater (mink, river otters) and marine (sea otters) species as well.

Narrowing things down to “weasels,” there is considerable confusion. For example, what weasels occur in Ohio? Where are long-tailed weasels located? Short-tailed weasels? Least weasels? And what the heck is an ermine or a stoat? First, all of the species I listed above are those that are supposed to occur in Ohio. The most common is likely the long-tailed weasel. It is the only weasel that we get on our camera surveys. This species seems to be doing well in most forested areas and responds positively to the lure we use. I would also think that least weasels would be attracted to our lure. Although the trail cameras are less likely to pick up very small critters, we frequently capture pictures of curious flying squirrels. These little guys weigh in at approximately 2.5 ounces. So, I still maintain the hope of capturing a picture of a least weasel. Nonetheless, I have seen evidence of their occurrence in southeastern Ohio. On at least four occasions, I have seen least weasel carcasses. In every case, they were killed by an outdoor housecat and then taken home and proudly presented to the cat’s owners. Nonetheless, I am unsure of their population size or their distribution. It is an unfortunate fact that we simply do not know much about the status of weasels in Ohio. We don’t know if short-tailed weasels are still residents of Ohio or if they have been extirpated and no longer occur in the state. Although extirpation would be unfortunate, the short-tailed weasel in Ohio only occurred in the northeastern corner of the state, which represented the southern extent of its range.

So, let’s get to this blog’s primary question. What exactly are the differences between a weasel, ermine, stoat, and mink? Well, all member of Mustelidae are technically part of the “weasel” family. However, I doubt I would call a wolverine a weasel. Here, the term weasel is used to encompass all species with “weasel” in their common name. For now, let’s put the mink to the side. Regarding what I call “true weasels,” they all turn white during the winter. This applies to long-tailed, short-tailed, and least weasels. Interestingly, the long- and short-tailed weasels retain the black tip on their tails even when completely white, whereas the least weasel has no black tip. Additionally, these species do not turn white, or not completely so, in the southern part of their ranges. Why turn white in places where it does not snow? Amazingly, the difference appears to be genetic. One researcher took a long-tailed weasel from a northern location to Florida and it still turned white in the winter. However, I am getting off track. Back to weasels in Ohio…how do they differ? Long-tailed weasels are largest at 12–14 inches long, short-tailed weasels are medium-sized (total length of males 9–13 inches, females 7–11 inches), and least weasels are smallest (total length less 10 inches in males and less than 9 inches in females). Long-tailed weasels have a tail longer than half their body length with a black tip, short-tailed weasels have a tail length about one-third the length of their body with a black tip, and least weasels have a tail length around one-quarter the length of their body length without a black tip. And here’s a fun fact: Only least weasel fur glows under ultraviolet light! Why…I have no idea but I’d really like to see it!

The next question is “what is an ermine or a stoat?" Some people, including fur trappers, call any weasel in its white coat an ermine. However, this is incorrect. Actually, the name ermine applies only to the short-tailed weasel. This is evidenced by its Latin name, Mustela erminea. The common name “stoat” also applies the short-tailed weasel, but it is more often used outside of North America for this wide-ranging species. Why does the short-tailed weasel warrant so many cool common names? I’m not sure, but I suspect it has something to do with their very extensive worldwide range.

Just one last thing to address. The mink looks much like a long-tailed weasel in its body shape, although it is a bit bulkier. It is also completely dark chocolate brown and lacks a white belly, a characteristic that occurs in all the “weasels.” The only white on a mink is a small patch on their chin and occasionally another small patch on the chest or stomach. Their tails are darker than their body, although the difference is often hard to see. Finally, they never change color, remaining chocolate brown year-round.

I hope I haven’t bored you too much. I’ve made my daughter’s eyes glaze over on many occasions when I started on a rant about weasels, minks, stoats, and ermine, to the extent that it has become an inside joke for us. This blog was actually her idea. Maybe she thought I’d get it out of my system for a while! But, yes, I am quite fond of the weasel family and there are many more amazing facts about them. I hope you find them as fascinating as I do.

Now a plug for our study! We are continuing our Carnivore Camera Survey on private land this spring. We are looking for participants, particularly in Pike, Meigs, eastern Washington, Noble, Muskingum, Guernsey, Harrison, Tuscarawas, Jefferson, and southern Coshocton. Please let me know if you’re interested in having your land surveyed. Also, we are purchasing new cameras this year (we previously used cameras borrowed from OU, which are no longer available). If you can help, please see our fundraiser at: https://www.facebook.com/donate/4817681431606383/855500091928118/

Every little bit helps. Thanks so much!!

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P.O. Box 396 Athens, Ohio  45701