Saturday, October 13, 2012

A weasel on the stink poles....

Mustelids are my personal "Holy Grail" when it comes to camera trapping.

For years I have went the extra mile for pictures of otters, mink, fishers and weasels.

Usually, my efforts go un-rewarded (they are a difficult group to camera trap 'round these parts!)....and although I've had some success with otters and mink, the others have eluded me.

Occassionally, gets lucky.

I *believe* this is a Long-tailed Weasel (Mustela frenata).  Unfortunately, the animal is pretty far away, but there are a few lines of evidence that would suggest M. frenata to me.  This species is slightly larger than the other weasels found in our area: the Short-tailed Weasel (M. erminea) and the Least Weasel (M. nivalis).  They can reach lengths of 18 inches and, based on the distance this one is from the camera (which would be about 15 ft), the size would indicate it's a Long-tailed.  Furthermore, according to Long (2008), the tail has a very distinct black tip, which is fairly obvious from these clips.  Now....the Short-tailed Weasel also has a black-tipped tail, but it is generally not found this far south.  Furthermore...and also according to Long (2008)......if the tail length is 1/3 or greater of the body length, it's a Long-tailed.  From what I can tell in this video clip, the tail length conforms with what I'd expect for M. frenata

Yet...there is one more wrinkle in all of this. 

This part of the state is also the unnatural home of a Mustelid introduced from Europe: The Stone Marten (Martes foina).  It was believed to have been introduced by a fur breeder in the '40s, and although apparently established, is not common.  For example, reports have trickled through that a few have been captured annually for roughly the last 15 years (Long 2008).  The Stone Marten's dorsal and ventral surfaces (or back and belly) are concolor (or...of one color), although, the limbs and tail fur is apparently slightly darker than the dorsal fur.  All three weasel species native to the area are bicolored (of two colors): with a brown back and a cream or buff belly.  Stone Martens do have a striking white patch on the throat, but no black-tipped tail.

It's hard to see for certain in this video, but I don't believe there is an obvious white patch on the throat of this animal...and it also doesn't appear that the belly/back are the same color.   Then...of course....there's the fact that the individual in these clips has a black tail.

Anyways.....I'm leaning towards Mustela frenata.

People are not kidding when they refer to weasels as bundles of energy.  Look at that thing go!

They have to be that quick if they want to catch some of their preferred prey items (which are also very quick) and avoid being eaten themselves.  Weasels prey upon many types of small animals, ranging from insects and snakes to small mammals.  Yet, rodents are often a favored dish.  In fact, they so frequently dine upon mice, that this behavior is even reflected in their genus name (Mustela), which translates to "one who carries off mice" (Cold 1998).  Long-tailed weasels are excellent examples of dietary generalists, and apparently readily switch to alternate prey when normal prey densities are to low.  According to a review by Sheffield and Thomas (1997) these generalist behaviors have resulted in their relatively stable populations.

Another cool thing about weasels and their relatives is that they don't shy away from bigger fare.  They are well-known to take down an animal as large as a cottontail.  Check out this footage of a "Stoat" from BBC's oustanding series LIFE, which includes a stunning series of one killing a rabbit (warning: this footage may be too intense for some viewers, but it is amazing!). 

Note: "Stoats" are apparently the common name used for Mustela erminea throughout the rest of the world, although in North America we refer to it as the Short-tailed Weasel (King and Powell 2007). question: weasels are very neat little critters.

I have never actually seen a Long-tailed Weasel before.  I've encountered Least Weasels several times in the past.  Well........I'm assuming they were Least Weasels given the fact that Leasts are found in the southern part of the state and like grassy or marshy habitats/forest edges where I encountered these (Long 2008). 

The weasels that I encountered were captured.....basically by accident.  They were all captured in funnel traps that I had along drift fences to catch snakes (this would have been back in 2006-2007).  We had been running these surveys for an entire summer and had been catching many small rodents in the funnel traps, in addition to snakes.  Then...suddenly....for a breif period (maybe a week or two), I caught four Least Weasels spread across two sites.

Two were completely alive and kicking (in fact, they basically ran circles loop-de-loop style inside of my minnow traps when I picked them up).  They were gone in the grass the second I opened the trap.

One, unfortunately, was dead upon my arrival (died from exposure), which I felt terrible about. 

The last individual appeared dead (at first) when I picked the trap up.  However, closer inspection revealed that he was still alive, but appeared groggy and suffering from stress/exposure/dehydration.  I didn't know exactly what to do...and of course I had no special gloves or anything with to deal with a critter like this.

But...against sound judgement.....I took it back to my car (in the trap).  I found a pair of extra socks in my car and placed the weasel inside one of my socks so that his head was poking out.  Then I poured a bit of water into the bottle cap from one of my water bottles and barely touched his chin with the water.  Immediately, the weasel started lapping the water up.  I continued to fill the little cap as long as the weasel would drink....and quit when he sort of coughed/sneezed a bit from the water. 

I tried to come up with some sort of a plan for this little guy.  He was still groggy (eyes closed), breathing seemed regular.....but he was listless.  I called a nearby vet clinic, but they said that they didn't deal with injured wildlife.  They told me to contact the Humane Society in the area....which I did only to find out they were closed.

So, there I was....with a sleepy-looking weasel in one of my socks on the front seat of my car.

Not knowing what else to do, I waited.  Eventually, the animal seemed to start perking up.  He opened his eyes, became semi-alert and looked like he might want to move.

At this point, I took the critter (in the sock) back out to the field location near the drift fence.  I found a nice protected spot under a dense growth of dogwood and placed the weasel there (in my sock).  I watched for a minute...but decided I didn't want to stress the animal out any I walked away.

Several hours later, I came back to find my sock laying there....uninhabited.

I hope that means the little weasel went safely on about his way.

Literature Cited:

King, C.M., and R.A. Powell. 2007. The Natural History of Weasels and Stoats: ecology, behavior, and management. Oxford University Press.

Long, C.A. 2008. Wild Mammals of Wisconsin. Publication No. 65 of the Museum of Natural History, University of Wisconsin-Stevens Point. Pensoft Publishers, Bulgaria.

Sheffield, S.R. and H.H. Thomas. 1997. Mustela frenata.  Mammalian Species no. 570.  Published by the American Society of Mammalogists.


  1. That's great footage. I've never seen weasels bound around like that (not that I've seen a lot of footage of them doing anything).

  2. This is my favorite entry you've written yet (or at least while I've been following)!

    I want to comment on the movement of the weasel- last year I learned they were bounders. And that BBC clip is awesome because a) rabbits are bounders b) weasels are bounding c) you can see them moving in tandem, in the same stride in that clip. I can't get over how long the weasel's stride is! Such awesome animals. I love the clips of them playing too- their bodies can just fold in half.

    Cool story! I found a LTW, dead, in the yard ~2 months ago. I just cleaned the skull, and now have a nice skull for my collection!

    1. I saw that post. Very cool to get the skull.

      I was able to get the skull from one of the least weasels that I found dead in a funnel trap.

  3. That's just a squirrel....just kidding around:) I love the bounding! That sure looks like a long-tailed weasel. They are like squirrels on caffeine though:) Awesome footage, and great story about the least weasel.


  4. Hehe, I like those shinny eyes bobbing around. Is it hiding behind the pole/tree? Classic! I hope we get to see more weasel action soon :)

  5. Thanks for reading, everyone!

    Henry, I don't know if he's actually hiding behind that tree...or if he's just using it as a vantage point? Sometimes I think weasels move so fast that their decision as to where they are going happens after they actually they are constantly re-adjusting, but quick enough to make up for an incorrect movement (of course that's pure speculation on my part :) ).

  6. I was interested to see a new (to me!) citation on the length of weasel tails. I have Whitaker and Hamilton 1998 "Mammals of the Eastern United States" and it states that frenata's tail isusually more than 45% of head and body length and erminea's tail is about 40% of the head and body length. Interesting....

    1. Hey JVN....

      Yeah, the exact text in Long's dicothomous key is as follows:

      "Tail over one third total length, usually 40%, with long black tip, rostrum of skull elongate, postorbital processes in adults prominent and pointed.....Long-tailed Weasel (Mustela frenata)

      "Tail less than one third total length, with shorter but distinct black tip, rostrum short, postorbital processes in adults hardly protruberant or tiny.....Ermine (Mustela erminea)"

      Long's book is a nice general source for information on wild mammals in the midwest....I recommend it!

    2. Great catch on the cameras. It is definitely nice to have to cameras in video mode. If they were in picture mode, I'm you would have had an even harder time telling what the blurry hoppy thing was. I hope this is a sign of more to come!