ACT's Nature Corner: How to Tell a Muskrat From a Beaver

The Kennebunk River overflows its banks, and the great beaver vs muskrat controversy ensues.

It’s funny how the ideas come for my Nature Corner articles, this one stemmed from a photo my neighbor took and posted to Facebook creating a whole hullabaloo.

Let’s set the scene. I live off the Downing Rd in Arundel on the Kennebunk River, a truly beautiful place full of wildlife in all seasons. I often walk with my husband and dog Clancy along the riverbank. However, in autumn our presence is not particularly appreciated by certain inhabitants. We’ll be walking quietly along and suddenly hear a loud SLAP and splash from the river. If we wait quietly for a few minutes, we’ll be rewarded with the sight of a fur covered head with dark eyes and small ears swimming away.

We’re not surprised at the sight of our beavers because we have seen evidence of their work in our basin. Trees are felled overnight in our small aspen grove. This fall we found a downed 10-inch red maple, with all its branches stripped, with distinctive beaver teeth marks. I’ve searched for a dam or lodge to no avail but do hear a small waterfall from a small creek coming from the Kennebunk side of the river. Our house sits on a ridge about 25 feet above a basin that may flood a few times of the year when the river overflows its banks. For a day or so we have a lake. No danger to us, with the house set up high but beautiful to view.

Just before Christmas this year, heavy rains caused the river to overflow. Below is a picture that shows what happens in our basin and along the river upstream of Downing Road.

Our neighbor Kirsten Read is a professional nature photographer, among other talents and took the amazing picture below, of six bedraggled rodents huddled together as the river raced by. Kirsten shared the photo with the neighborhood and posted it to her Facebook page. Then the excitement started! I had assumed they were beaver, flooded out of their lodge, because I had seen beaver in the river in the past. Many others, replying to the Facebook post were certain they were not beavers but muskrats. Evidently the Facebook replies got quite intense and at times heated. When I heard, I thought what a great idea for this article about “how to tell a muskrat from a beaver”.

The first difference is size. Muskrats are much smaller than beavers weighing between 2-5 pounds and are 16 to 25 inches with half of that being tail. where beavers average about 40 pounds ranging from 25-60 pounds and can be 35 to 48 inches long. The picture however doesn’t include anything to gauge actual size. Was the log 8” or 16” in diameter? The second most obvious difference is their tails. Beavers have a wide thick paddle like tail with scales, but muskrats have a long skinny tail.

I didn’t see any tails, they seemed obscured by the branches. If you look close at the furry guy on the right and zoom in I think we may have our answer. That looks like a skinny tail to me. What do you think?

Let’s look at other ways these two animals differ. We’ve already discussed how their size and tails are very different but there are many other ways they differ.

While swimming, a beaver will generally only have its head above water. Their ears are also easier to see than a muskrat’s. Watch this video of a beaver swimming.

In comparison, the entire body of the muskrat and its tail is usually seen as they swim, and they have tiny ears.

Check out this video of a muskrat swimming.

Muskrats generally live 3-4 years while beaver live between 10-15 years. Muskrats have up to 3-4 litters per year while beaver have only one.

Both by necessity, live by water but beaver prefer lakes, ponds, and rivers. Muskrat generally prefer marshes, swamps, and other wetlands

Both animals build both burrows in river banks and lodges the muskrat lodge is generally made of grasses and cattails and is much smaller than the engineering marvel of the beaver. Furthermore, muskrats don’t build dams because they don’t have teeth strong enough to chew wood like a beaver.

The teeth of a beaver are incredibly strong due to the large amount of iron in their teeth that also give them their distinctive orange color. Their teeth grow continually throughout their life as they are worn down chewing wood.

Beaver create a pond by damming a waterway. They then collect twigs sticks and branches and make a large domed pile in the pond. They then hollow the pile out to create a multi-level living quarters with at least two entry/exit tunnels and a vent hole at the top. Sometimes muskrats will live together with beavers in the lodge.

The eating habits of the two animals are also different. The beaver is an herbivore and eats only plant material. The muskrat on the other hand is an omnivore with a more varied diet. Muskrats also eat plant material but also frogs, small fish and crustaceans and any other treats they may find.

In the fall beaver will collect leafy branches and stick them in the mud underwater by one of the entrances to the lodge. During the winter, they will bring a branch inside to the eating area of the lodge for the group. Muskrats do not store food and must forage. They build underwater channels or canals from their lodges to search for food. They may open a small hole in the ice and cover it with grasses, called a “pop up” as a safe place to rest as they hunt for food before returning home.

Neither animal hibernates during winter but remain active. They both have insulating coats that keep them warm and waterproof. The muskrat has a double coat; the undercoat is dense and silky; it’s covered by a second coat of guard hair that is thick and waterproof. Beavers have a gland at the base of their tail that secretes a substance called castoreum. To access the castoreum they sit upright while sitting on their tail and spread this waterproofing substance with a special grooming claw on its hind foot. They work with other in their family to groom each other’s backs.

Muskrats also secrete a special substance. It produces a “musky” scent that gives muskrat its name. It is used by the animal who is much more territorial than beaver to mark their territories.

So, do you think you can now tell the difference between a muskrat and a beaver if you were to see one? The first thing you have to do is get out and explore. Do any of you know where folks might find a beaver lodge to observe? Or perhaps you have some photos to share? I’m on a mission to find a local one this summer. I’m going to start by finding the source of the waterfall I heard this spring.

Please feel free to comment on my article and suggest other articles you’d like to see in the future at info@arundeltrust.org

Joan Hull

Maine Master Naturalist