Will Beavers Eat Fish? The Science Behind Their Diet

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Will beavers eat fish?

Beavers (Castor canadensis) are an iconic species of aquatic mammal that most people can easily recognize. Living in Alaska, I regularly see beavers swimming around lakes and ponds when I’m out hiking or camping.

But because beavers are primarily active at night, most of us don’t have the opportunity to witness beavers eating.

Given that they spend the majority of their lives in and around water, it leads many people to wonder, will beavers eat fish? While many aquatic mammals will eat fish, such as river otters (Lontra canadensis), beavers do not.

Thankfully, wildlife biologists are able to study beaver diets from analyzing their feces (or as we like to call it; scat) and camera traps.

In the article below, I’ll dive into the science and help answer exactly what do beavers eat to survive.


Will Beavers Eat Fish?

Beavers are aquatic mammals that spend their entire lives in and around water. And while I’m sure a beaver has, at one point in history, incidentally eaten a fish, they are not carnivores (i.e., meat eaters) but instead are strict herbivores (i.e., eating plant materials).

NPS Photo

Beavers are not adapted for chasing fish in the water, nor are their teeth adapted for capturing and chewing on fish. A beaver’s teeth are typical of an animal that eat herbaceous materials and not for ripping, tearing, or chewing on meat.

River otter skull on the left, beaver skull on the right

As you can see in the above picture, a river otter’s teeth (on the left) have sharp canines for grasping prey, and sharp back teeth for tearing meat.

The beaver’s skull (on the right), on the other hand, has sharp incisors for chipping away wood, and flat back teeth for grinding and chewing plant materials.

But do beavers eat meat of any kind? Because of their teeth and the anatomy of their guts, beavers are simply not adapted to eating fish or any other type of meat.

So, will beavers eat fish? Nope! But if not fish or others types of mean, then what do beavers eat?

What Do Beavers Eat?

Beavers are generalist herbivores that eat a variety of leaves, twigs, and bark from woody plants that grow near the aquatic environments they live in. But beaver diets can differ depending on what type of water they live near.

What do beavers eat
NPS Photo

One study found that beaver diets, in general, consisted of 60-80% aquatic plants. But the study also found that beavers living in ponds consume higher levels of aquatic plants during winter than beavers living in steams, which ate more terrestrial shrubs.

Beaver diets also vary seasonally with higher levels of aquatic vegetation in summer diets, and more shrubs or trees during winter. Aspen and alder have been shown to be a preferred food during winter. While there is a lot of variation in the types of woody vegetation beavers like to eat, they prefer deciduous trees over conifers (aka evergreens).

In the fall, beavers cut down trees to begin caching woody food for the long winter ahead. As long as beavers can get through ice on the ponds or creeks they live in, they can continue cutting down trees in winter. But where I live in Alaska, they need to have their cache fully stocked for winter given the thickness of ice!

Do Beavers Eat Wood?

The short answer is yes. But they don’t eat all portions of the trees and shrubs they cut down. Beavers primarily rely on the bark of trees they cut down, and not on the main portion of the tree we typically think of as wood.

Do beavers eat wood?
FWS Photo
FWS Photo

As you can see in the picture above on the left, the beavers cut the tree down, but began to naw at the bark. Beavers will eat the bark at the area they fell bigger trees, but can carry smaller trees and branches back to their lodges to eat.

The bark is much easier to digest and has more available nutrients than the wood itself. They will eat smaller woody stems, but not wood chips from bigger trees.

So when you see a beaver cutting down a tree with its teeth, it’s not because it’s eating its dinner. It’s either cutting down the tree to access more of the bark or smaller branches further up the tree. Or, they are cutting down the tree to help build their dam or lodge. Although those are mostly made of smaller trees that they can easily moved and placed in the right location.

Summary

Beavers are one of my favorite animals just because of how industrious they are and how well adapted they are for living in their aquatic environments.

While it might seem like they would eat fish because they live in the water, they are actually herbivores. And even though they spend a lot of time cutting down trees, their preferred foods are generally aquatic vegetation.

Woody vegetation still makes up a large portion of their diet, but primarily in winter when aquatic vegetation is less available.

Wondering about other animals that are adapted to living in aquatic environments? Read my post where I address the question “Can moose really swim?” Curious to learn other interesting facts about wildlife?. Check out my other Wildlife Information posts.

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AUTHOR
Ryan has Ph.D. in Wildlife Biology with over 20 years of experience working in the field. He has published dozens of research articles in scientific journals and has worked on a variety of animals ranging from ground squirrels to polar bears. He has also been recognized by The Wildlife Society as a Certified Wildlife Biologist.