Author’s Note, March 29, 2022: Seven years after I first published this article, it remains the most popular page on my website. I have updated it to include new and larger photos, and continue to welcome comments and questions below! I have also added a reader note regarding nutria at the bottom of the page.
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?
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.
Out of Water
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 photos 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…
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?
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. When they run, their bodies practically undulate like a slinky. 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 one of 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 (even more than a beaver’s), and otters sport long bushy whiskers. I mean, really… is this an otter pup or Wilford Brimley?
In the Water
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.
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 look at the swimming beaver photos above. 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.
Yup, even baby beavers have protruding ears.
So what about river otters in the water?
They’ve got those protruding ears like a beaver, but notice how the nose is even bigger relative to their head size?
The main difference is that with swimming river otters, you often just see the head and neck, not the full length of the body. In fact, they are able to raise their head and neck up above the water to “periscope” and investigate their surroundings.
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 in the photo below–there are four total–doing just that. Its head is underwater. In the next photo, one otter is just diving under the surface as they speed along.
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.
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
– Does it have a tiny nose? Yes
– 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
– Does it periscope when checking me out? Yes
– 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.
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!
Update March 2022: Last year reader Steve Swienckowski sent a photo of a mystery animal seen near his home in Raleigh, North Carolina.
Steve noted that it was larger than a muskrat, but the skinnier tail seen here, as well as stunted head and neck, combined with a thicker back half led me to guess that maybe it’s a… Nutria? It’s an animal that, along with the mink, I never discussed in the original article, but they are invasive in the US and are found in more and more areas (we have them here in the PNW, but I’ve never seen one). For a nutria size comparison, check out this page from the California Department of Fish and Wildlife. The third photo down shows a good lineup with both beaver and muskrat (note, however, that the nutria in that photo has only half a tail).
Other Animal ID Throwdown Articles:
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.
Visiting in the Adirondacks we had the pleasure of watching a what we know now after ur report was a big beaver at work.
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.
I would love to see the side by side comparison picture of the muskrat and beaver. Having trouble figuring out which.
I am interested in seeing the picture of the two of them in the same frame please
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!
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!
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.
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
This was really fun and informative, thanks!
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!
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.
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.
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
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
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.)
Thanks for the info and photos, but muskrats are omnivores.
Great article, Max! I cam across this when researching the differences between a nutria and muskrat. Because I’ve seen nutria in the south, I incorrectly identified a muskrat in Yellowstone as a nutria. Muskrats are a lot smaller than a nutria, with a thin vertically edged tail. A nutria, is bigger than a muskrat and has a snout like a beaver but no protruding ears. There are a few more differences between each species so if a person is in a part of North America where all three live, well, they’ll want to do more research. haha
Agan, great article and photos.
Great article. Watching a lone creature waddle up to the small pond in my back yard this morning, I assumed it was a muskrat. But then I got more curious, knowing there are river otters in this county I found your article. The seem to head to my pond nearly every fall sometimes staying for the winter. Thanks for all the helpful info and wonderful pictures.
Almost sure that what we see in the pond behind our house is an otter, The legs aref furry & the tail is not beaver like. It stays under the water/ ice for a long time.It brings up frogs or fish & climbs onto the ice,. to eat its prey by holding it in its paws. Its head looks similar to a seal with ihe whiskers. I have not been able to get a picture as it stays in the middle of the pond We have lived here in Easton for about 15 years & have never seen this animal in the pond.
Wow well written. Now I’m confident I can tell them apart 😂 thanks so much!
I once called my mother and asked, “What looks like a beaver, but without the big tail?” She said, “Is this a riddle?” “No, the dog brought me something dead and I don’t know what it is. It really looks like a little beaver with a skinny tail.” I replied. There was a pause, “It is a muskrat?” “Yes! Ohmygosh! Thanks!” I said. Oh that dog used to bring me such bizzare things. He had a turtle he brought me(alive) for several years. I always knew it was the same one because it had bite marks on the shell. I’d take it back to the slough and let it go again.
Based on your article I am guessing River Otter. Unfortunately it was at a distance and moving fast and disappeared under boardwalk/bridge. Consequently I had no time to focus. Jamestown Island James River. VA. I would love to have confirmation or correction on my guess from someone with more experience.
I would like to e mail photos but not sure how in this format. Thanks for any help.
Thanks for the great information. Our house on a lake in Nova Scotia is frequently visited by beavers, and I have to cage our small trees to keep them! A few days ago we had a the head of a large fish (catfish, I think) left on our dock and wondered how it got there. We thought maybe an osprey dropped it. Well today we found the culprit – an otter! Never seen one here before, quite exciting.
Thanks for the great write up about these aqautic animals. Your desciptions and photos helped me confirm a Muskrat was what I saw today in NJ (Crater Lake, Walpack, NJ right near the Appalachian Trail). Considered a Beaver but did not see any evidence of chewed vegitation around this lake as I have seen at other locations.
I actually saw the Muskrat breach, probably going after a small fish, and I had remembered Beavers were Herbivores so had honed in on Muskrat but you post confirmed it.
BTW I know a Waugh family personally. Originally from Australia, moved to Rochester, NYin the 60’s then Northern NJ in the 70’s. now just the 3 boys all my friends on Facebook, facebook.com/mrsnib. Feel free to find them on my timeline and reach out using me as a contact or friend me and I’ll introduce you.
I really enjoyed this excellent comparison, and your beautiful photos. It is well-written and helpful.
I have questions about behavior of otter vs muskrat. I have seen both muskrat (often), and beaver (occasionally), in the pond near my house (south central Maine). Today I think I saw an otter. I thought it was a muskrat, at first. A few things differed from muskrat behavior I’ve seen. It raised its head and neck vertically out of the water. Sometimes it dove like a porpoise, but at other times it disappeared backward into the water – rearing up, and sinking straight down. It also seemed more active, as you mentioned, and more curious. Usually the muskrats just scram as soon as they notice me. This critter stayed around, repeatedly rising up, diving, and reappearing, looking in my direction, while moving past the dock where I was sitting with my dogs. I have heard otters, snorting, elsewhere, but did not have my hearing aids in, today, so I don’t know if it snorted.
It did seem longer than a muskrat, but that’s hard to tell at a distance. Sometimes it swam with head and tail showing, and a few times I saw its body as well.
This is very helpful! Thank you!
Your information was very helpful! Thank you so much.
This was so helpful, thank you! I’m with my kids in the San Juan islands and we were able to figure out that we saw an otter (we are pretty sure now!)
Thank you for your photos and tips.
I live in eastern North Carolina, where we have nutria, an invasive species, along with otters. Any tips on distinguishing between the two when they are swimming? I am guessing that the clues you gave for muskrats and beavers would apply to nutria.
Today in South Jersey on a 10 mile kayak run in the first three miles we kept seeing the same little face looking at us from behind some sticks close to the bank in the water. I couldn’t see any whiskers because it was always facing the current. Too curious to be a beaver? I thought otter, bc face grayish in color, also, I was able to make eye contact with it and it was non aggressive. Beaver usually slap tail or hit bottom of the kayak. This just ducked under and then we’d see him again further along the route. Do otters make a soft chitter sound?
we just moved into our new home North of Toronto (in Ontario) and there are small creatures that are either Muskrat? Mink? Otter? I can’t tell–haven’t gotten close enough to them. But some things: do live in a group–live under the ice in our pond in winter and when they travel across the pond they move more like otter (slinking up and down in a “S shape” –where the S is sitting on it’s side–if that makes sense). When it swims it looks more like beaver (I think)–just can see the head? (We have beavers at my cottage, and this creature is not a beaver). Does the movement on the ice help with what it is? Thank you!!
On the Pend O’Reille River in North Idaho we have beaver, muskrats and otters. Not sure about nutria. The otter seem easier to identify. After reading your articles and viewing your pictures, i am still uncertain. These two i am now observing who appear to be nesting under my cedar log dock lead me to muskrat, though they seem fairly large. They go out about 40 feet from the dock and float with most of their body visible. Then they dive and i think are coming up with vegetation When swimming back toward me, i could distinctly see the tail acting as a motor at the surface of the water, not submerged. I would think the tail would be telltale,so to speak, but it doesn’t look as wide as a beavers should be but thicker than what i would think of as a rat’s tail. Do mustrats or beavers, or both, power their swimming with their tails at surface level? Thanks. Now i don’t feel so bad at being confused.
So glad I found this page! Thanks so much for this! My husband and I just got back from Yellowstone yesterday and had a few ID issues with some of the animals we photographed. We hiked Trout Lake (what a fun hike to capture the little creatures of Yellowstone!) and took some pics of what I thought was a river otter and what my husband thought was a beaver. Well, he won, it was a beaver. Gonna go check out the coyote vs. wolf article of yours now. 🙂
Ok, but what are the sound differences. I have been looking all over the internet to figure out which of these animals I heard. I was doing a creek walk in the northern sierra area when I came across some kind of animal. I heard splashing, but it was too far to get a good look at other identifying characteristics. But as I came closer I heard a low hum or purring that I think was a defensive growl. What are the different defensive noises each of these animals.
There’s a critter I’ve been seeing at my place on the Detroit river for a few years. Although there are reported to be beavers across the way on Belle Isle, I think it’s more likely a muskrat or an otter. The pictures and descriptions here point to otter. I’ll have to reassess this next time I see dude.
Do Muskrats chew down trees?
I live in wilderness in Canada. I have a beaver pond and canals. There is flooding too. My favourite place is down in that area sitting watching and walking around. Amazing dams have been built. It is completely isolated.
I see evidence of beavers, but never a beaver. I understand that they are nocturnal, any advice on how to observe them? Being out at night can be dangerous, because it’s so black dark and there are wolves and bears etc.
I am very anxious to preserve and enhance the environment for the beavers. Any advice.
Can beavers and muskrats live in the same environment? I do hope so.
I live on Manitoulin Island, Ontario in Canada in wilderness on the island.
I wish each of your photos was marked with the name (Beaver, Otter, etc.) — Sometimes you mentioned more than one in the description preceding the photos, and maybe mentioned one (Beaver, Otter, Nutria, Muskrat, etc) in the paragraph following the photo. I found this confusing.
Your article was amazing. I live on a slow moving river and get to experience lots of wildlife. I was quite impressed with my identifications of the beaver, otters and muskrats that frequent the river. The last couple of days I have been perplexed by what I am seeing. I could not tell what it was. Did not seem lg enough to be a beaver. Not frisky like an otter abs not small enough to be a muskrat. I finally spied it out of the water abs it looked like …. A ground hog!!! Smaller than a beaver… looking at the tail It was not long like an otter and not wide like a beaver. It was sort of short abs was hairy!! Any ideas??
And what about otter vs marmot?
Thanks for this instructional article. I’m having trouble with an ID and was hoping you could help but I can’t find a way to attach images. The photos were taken in Harwich MA on the Herring River. I’ve never seen any evidence of Beavers, i.e. dams or felled trees but your description and images of the ears and most of the body out of the water make me think it’s a Beaver. Muskrats and Otters are found in an adjacent freshwater pond so I presume it’s one of those, although the ears look too large. Is there anyway I could send you the images? Thank you.