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Animal Identification Throwdown: Otter vs. Beaver vs. Muskrat

Every spring when I visit Yellowstone, it’s a tradition to hike to Trout Lake to search for river otters.  Trout Lake is historically the most reliable spot to see otters in the park, but the best time is generally in early summer, not spring.  Usually around mid-June visitors begin to see otters at the lake with relative frequency.  This happens in large part due to the trout spawn, which provides an easy source of food for the otters and their pups.  The spawn lasts into July, giving people a few good weeks of otter fun.

The question of otters at Trout Lake is not usually if, but when?  When will the otters arrive at the lake (which is often frozen over into late spring)?  When will the pups–if there are any–make their debut?  When will the trout enter the inlet to spawn so we can get close views of the otters chasing, catching and eating them from only a couple dozen yards away?

Sightings in May and early June are not common, but I always try to get up to the lake (as well as neighboring Buck Lake) to see if I can get lucky.  Though you never see otter pups that early, I have found adults in both lakes during past spring visits.

This May, I made my usual early hike up to the lake, but didn’t see any sign of them.  But in early June another park visitor wrote in his online trip report that he’d seen an otter at Trout Lake.  So my hopes were buoyed, and I returned to the lake a couple times with clients in subsequent weeks in hopes of getting lucky.  We found nothing.  Even by the third week of June, there was no sign of the otters, not even any scat.  I figured it was just bad luck.  Time of day seems to matter very little to otters.  I’ve seen them out at 6am and 6pm.  I’ve seen them out at 8:30 in the morning, and 2:30 in the afternoon.  They come and go as they please.  So this year I figured I just missed them.

Fast forward a few weeks: the visitor who had reported the original sighting finally shared his photo of the otter.  It was actually a muskrat.

Things started to make a little more sense at that point (e.g., why I couldn’t even find scat at the lake), and though I’m not a big fan of dashing dreams and hopes and tempering the enthusiasm that comes with “cool” sightings, I felt compelled to point out the correct animal ID.  And that’s when someone else chimed in and insisted the animal in the photo was… a beaver.

It looks like we have an Otter vs. Beaver vs. Muskrat Throwdown on our hands!

This wouldn’t be the first time there’s been confusion when it comes to identifying these animals, and mistaken animal IDs in Yellowstone are quite common.  Coyote vs. Wolf, Cinnamon Black Bear vs. Grizzly Bear, Juvenile Bald Eagle vs. Golden Eagle, Marmot (or even Wet Badger) vs. Wolverine.  I’ve heard a lot of mistaken IDs over the years, and have certainly made my share of slip-ups when seeing some animals at first glance.

Muskrat vs. Beaver happens a lot.  River otters sometimes get thrown in the mix, depending on what people hope they’re seeing.  They’re all brown, furry and they swim well so the confusion isn’t too surprising.  Can you tell the difference and identify the following three animals?

Muskrat swimming

Beaver swimming

Otter swimming

If you answered Muskrat, Beaver, Otter, you are correct.  There are some similarities when they’re swimming, to be certain.  But out of water, it’s a completely different story.

Muskrat

The muskrat is the smallest of our furry aquatic trio.  Of course, we don’t generally have the benefit of a side-by-side comparison when we see these animals in the wild, so saying one is “big” and one is “small” may not help you much.  But trust me, muskrats are significantly smaller than the beaver or otter (a difference of two feet in length–including the tail–versus three to five feet).  Muskrats can still look beaver-like out of water, especially when they’re sitting, all balled up and fuzzy.  But in the photo above, you can see the main difference between the two that will help with your ID (aside from size): the tail.  Muskrats have a long skinny tail.  Sometimes when they’re swimming, the tail may be curved slightly out of the water, or even pointing straight up, as erect as an antenna.

Beavers, on the other hand…

Beaver

Look for that wide, flat tail.  A dead giveaway that it’s a beaver.  They’re also much more rotund than muskrats.  And what about otters?

Otter running

It’s a whole different body type when you see it out of water.  First, they’re long and slender, looking downright “athletic” compared to the other two.  They’ve also got fur from head to toe to tail.  No bare feet, and no scaly tail.  Remember, otters are actually mustelids (members of the weasel family), while the muskrat and beaver are rodents.  Like many weasels, otters are energetic and active.  You can often ID an otter simply based on its antics!  This, of course, is one of the main reasons they’re my favorite animal to photograph in the park. 🙂

What else differentiates an otter?  Well, if you see it close up, the nose is very prominent on the face, and otters sport long bushy whiskers.  I mean, really… is this an otter pup or Wilford Brimley?

Otter pup or Wilford Brimley

Visual comparisons on land are fine, but the original debate originated from a photo of a swimming animal.  So let’s go back and look at a few more examples of these critters in the water, and identify a few final clues that can help you with your spotting.  We’ll start with the muskrat and beaver, since they are the most similar in appearance.

Muskrat in water

Beaver swimming

Both of these rodents swim with most of their body length visible.  They typically appear very flat along the surface of the water.  Again, ignoring the size difference, you can look instead to the length of the body relative to head size.  The muskrat’s head and body are relatively compact.  But go back and look at the first swimming beaver photo posted up top.  The beaver’s body extends well beyond the head.  This is a large animal (North America’s largest rodent!), so there’s a lot of body trailing in the water.  The other thing to look at is the ears.  As you can see, the beaver has larger, more prominent ears than the muskrat.  The nose is also noticeably larger.

Baby beaver

Yup, even baby beavers have protruding ears.

So what about river otters in the water?

River otters

The main difference is that with swimming river otters, you often just see the head and neck, not the full length of the body.  I’ve seen this with neotropical river otters and giant otters as well, not just our North American variety.  Otters have more of a curved form in the water, with most of the body and tail riding just beneath the surface.  When they pick up speed they’ll often start “porpoising,” or making shallow dives as they race through the water (you can see the far left otter–there are four in this photo–doing just that… its head is underwater).  Generally, otters will dive much more frequently and will be much more energetic than the other two, just as they are on land.  You’re much more likely to see them traveling in groups, especially in larger rivers and lakes.  Though beavers and muskrats will be seen in larger family groups, they’re usually spotted alone or in pairs.

Otter with fish

Of course, if it’s swimming with a big fish in its mouth, that’s a dead giveaway.  Beavers are herbivores, and while muskrats are omnivorous, they are usually seen consuming vegetation or much smaller critters.

So, if you see a furry swimming thing in Yellowstone’s lakes or rivers, ask yourself the following questions:

– Can I see the whole body flat along the surface?  Yes
– Does it have protruding ears?  No
– Is it small (1-2 feet body length)? Yes
– Is it feeding on grasses or diving for aquatic plants?  Yes

Likely answer: Muskrat

– Can I see the whole body flat along the surface?  Yes
– Does it have protruding ears?  Yes
– Is it bigger (2-3 foot body length)?  Yes
– Is it feeding on willows or carrying large branches while swimming?  Yes

Likely answer: Beaver

– Can I see the whole body flat in the water?  No
– Is it traveling very fast?  Yes
– Is it traveling in a group?  Yes
– It is catching fish, snails, salamanders or leeches?  Yes

Likely answer: Otter

– Can I see the whole body flat in the water?  No
– Does it have protruding ears?  Yes
– Is it bigger (2-3 foot body length)?  No, it’s actually much bigger!

Likely answer: Oh, that’s a bear.

Swimming grizzly bear

Edit: Someone asked about how the mink fits into this group, so I wrote a follow-up article on that species.

Update June 2016: Reader James Kibler provided these images of a beaver and muskrat side-by-side, photographed in New Hampshire.  Check out the difference in size!  Thanks James!

Beaver and Muskrat by James Kibler


Other Animal ID Throwdown Articles:

Wither the Mink?

Gray Wolf vs. Coyote

28 Comments

  1. Holly August 29, 2015 Reply

    Very useful information, exactly what I needed. I guess what I saw was a muskrat… about 18 inches from nose to tail, but its tail was short and thick and seemed to be hairy – maybe I misperceived that in the water… could it have been a baby otter? There are at least three of them in the pondy-marshland I where I observed them; but there may also be what looks like maybe muskrat mounds in the pond. The prolific scat all around makes me think… omnivore, and maybe from a creature that is about oh, estimate 15 pounds or so. But no possible candidate has the short, thick, hairy tail-rudder I think I observed. The marshland is fed by a stream that is supposed to be a salmon byway…. that might be more ottery habitat. Plus, the name of the area – roads, schools, shops – many have “otter” in them – which could be a relic from ye olde days. I’ve seen two smaller and one large of these swimming mammals. No beaver sign at all. Still no 100%, but my working hypothesis is now: muskrat, based on the my assessment of highest likelihood.

  2. Carolyn September 19, 2015 Reply

    Visiting in the Adirondacks we had the pleasure of watching a what we know now after ur report was a big beaver at work.

  3. James Kibler April 12, 2016 Reply

    This is awesome, thanks! I took a photo this morning that could be helpful for perspective… It shows a beaver and a muskrat in the same frame, swimming past each other in opposite directions… If you’re interested let me know and I can share it with you.

    • Peter Barber June 25, 2016 Reply

      I would love to see the side by side comparison picture of the muskrat and beaver. Having trouble figuring out which.

      • Author
        Max June 28, 2016 Reply

        Peter, I’ve updated the post to include James’ photos at the bottom of the page.

    • Linda June 16, 2017 Reply

      I am interested in seeing the picture of the two of them in the same frame please

      • Author
        Max June 16, 2017 Reply

        Linda the photos are at the bottom of the article.

  4. Vicki June 28, 2016 Reply

    Thanks for your great explanation.. So had breakfast watching about five otters. When I walked down to lake side to see better lots of growling noises as they looked at me. Lower Trilipe Lake Cass Co. Minnesota. Got pics and video!

  5. Katherine Hauswirth October 4, 2016 Reply

    Thanks so much for this. I have been watching what I think are muskrats in a local pond, Then one day, recently, I was seeing so much of their tails, and very active tails, and started to wonder if they could be beavers. I was feeling sort of inferior about this since I am such a nature lover and nature writer and it seems I really should know! I will study your photos and tips more; leaning towards muskrat but very grateful for the help!
    Katherine

    • Author
      Max October 4, 2016 Reply

      Glad this could help, Katherine!

  6. Katherine Hauswirth October 7, 2016 Reply

    Max, it’s Katherine again. I am working on a book of essays on nature. It will be my second; my first (The Book of Noticing: Collections and Connections on the Trail) will come out with Homebound Publications in May. Can I have your permission to use your checklists from this post (including the bear, for a laugh!) in my book? Again, many thanks.

    • Author
      Max October 7, 2016 Reply

      Katherine, it’s probably best to email me about this.

  7. Mary Ann January 16, 2017 Reply

    Thank you, this was so helpful. We recently bought a little house in the mountains of Georgia with a little lake. I wasn’t sure what I was seeing but it seems that they are a family of Otters!! You made the identification much easier. Thanks again

    • Author
      Max January 16, 2017 Reply

      You’re welcome, Mary Ann. I wish I had otters in my yard!

  8. Kirsten February 1, 2017 Reply

    This was really fun and informative, thanks!

    • Author
      Max February 4, 2017 Reply

      I’m glad it helped, Kirsten!

  9. Leslie A Barrett April 1, 2017 Reply

    Thank you for such an informative article. I haven’t been able to identify our critter on the pond yet. I’ve only seen it in the water at dusk. I finally got a few pics yesterday, but still too far away. Leaning towards otter, swims pretty fast, and dives under like you explained. They are in Ohio, but none have been spotted in Lorain county. I’m hesitant to notify anyone (Been watching it since December 2016)due to our HOA recently did something to get rid of the Canadian Geese and swans that live here. Now they are clearing both sides of the pond, destroying nests, cutting everything down to the ground. They are destroying habitat for everything else. If they find out it’s an otter on the pond, eating their fish(they stock the pond), I’m afraid I won’t see it anymore. I’ve already found dead muskrats that someone killed a few years back.
    I’ll be going back today, armed with the info you provided, hoping to get a better look! Thanks for the side by side pics, very helpful! He’s just so fast, as soon as he pops up, sees me, goes back under! Wish me luck!

    • Author
      Max April 1, 2017 Reply

      Good luck, Leslie! If you do manage to get photos, I’d love to see them, even if you’re not sure what it is. 😉

  10. Polly April 30, 2017 Reply

    Thanks for this helpful comparison of otters vs. muskrats. Early this morning on the Damariscotta River in Maine I watched a muskrat (I think!) about 50 feet out on the tidal mudflats, foraging for little crustaceans (I assume! No vegetation there). Had never seen a mammal so far out in the mud. Too small for an otter, tail too skinny for a beaver. As the tide started to come in, it dragged its way, heavy with mud, back toward shore and out of sight.

  11. Polly Allen April 30, 2017 Reply

    Thanks for this helpful comparison of otters vs. muskrats. Early this morning on the Damariscotta River in Maine I watched a muskrat (I think!) about 50 ft out on the tidal mudflats, foraging for little crustaeans (I assume! no vegetation there). Had not seen a mammal so far out in the mud before. Too small for an otter, tail too skinny for a beaver. As the tide started to come in, it dragged its way, heavy with river mud, back toward shore and out of sight.

  12. Kindra June 6, 2017 Reply

    Loved the comparisons article, thank you. Still at lost as to what we saw up at Tetons along a river yesterday. I would say there was a beaver dam near and this critter popped up out of the water and bobbed for a bit (kind of waving at us) as if he was standing on his back legs in the water. Watched us as we tried to get a picture…a fuzzy one is all we got. I still say otter by his actions and I think skinny but your timeframe says it is too early. My husband says a beaver so I have come to call it the critter viewing

  13. Mrs. Quick July 15, 2017 Reply

    Dear Max,

    Thank you for the wonderful info
    And pictures that described so
    Well, every creature that I have been researching. They are all so very interesting, in their own right. Both the “Little People” and the “Little Brother” fascinate me.
    I would like to write about them.
    Thank you again. Mrs. Quick

  14. Margie August 3, 2017 Reply

    Dear Max,
    Thank you so much for this! I just got back from my family’s camp on Boyden lake in Washington County, Maine, where my cousin and I had a wonderful time with what we called our “Muskratology” discussions in the evening. We’d sit out in the netted tent in the evening, safe from the buzzing mosquitoes, and watch for the muskrat to swim by–nearly always exactly at 8:15–as a muskrat has been doing for thirty years, according to my father’s camp journals. My cousin saw an otter one day, which threw us into a frenzy of trying to sort out the differences. You’ve helped immeasurably! (Love the tip about the muskrat’s tail sometimes being straight up as it forages; I saw that one evening and started to doubt myself. Thanks.)

  15. Megan August 10, 2017 Reply

    Thanks for the info and photos, but muskrats are omnivores.

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