Mountain beavers: the oldest living rodents

By Janet Carroll | Jul 25, 2012
The mountain beaver is a foot or so long, weighs about 2-3 pounds, and has a long clawed toes and a stubby tail.

The Pacific Northwest is home to the mountain beaver, considered the world’s oldest group of living rodents. Fossils of theirs have been found that are thousands of years old.

Interestingly, paleontologists indicate that the mountain beaver has not made adaptations in physical form and structure over time as other animals have.

The mountain beaver is not related to our dam building beaver, but rather to the squirrel family.

It is also not restricted to the mountainous areas, so how did it get its name? No one really knows.

A few months ago, I was at my usual spot at the window having coffee and watching the birds at my feeder, when I saw one!

A little furry creature was nibbling on the branches of my evergreen huckleberry. A gray squirrel came over to check out the activity – and then the mountain beaver moved into full view.

They are cute and cuddly looking, but they can be ferocious if you corner them or try to catch them.

I knew that the mountain beaver was around because it ate the new growth off vine maples, and I saw a tunnel hole, but this was the first time I actually saw it among my backyard plants.

When I first moved into my home, I was walking down a side slope, scoping out the Himalayan blackberry removal project there. I stepped into a mountain beaver burrow and fell to the ground.

This little animal can develop quite an underground network of burrows for living and nesting, and they are often used by other animals.

Once I started getting rid of the blackberries, the mountain beaver left, but now that the slope has grown in with salmonberry, blackcap, sword fern, and elderberry, the mountain beaver is back.

Mating season is the only time that mountain beavers are together. The rest of the time, they are solitary animals.

Many people do not want mountain beavers around their home because its maze of underground burrows can destabilize a slope, and it will eat landscaped vegetation.

I again refer you to the book “Living with Wildlife” by Russell Link for information about how to deal with animals that are causing problems.

My property is a small wildlife sanctuary, so I am OK with mountain beavers. As long as creatures are native, I will enjoy them.

I recently met a like-minded Mukilteo resident who has a video on her cell phone of a mountain beaver eating one of her shrubs, which did not bother her at all.

It is very exciting to have such an ancient creature living in the steep slopes and sandy soils of my property!

Janet Carroll is a member of the Mukilteo Wildlife Habitat Project. After two years of getting landowners to certify their yards as wildlife habitat and conducting educational activities, Mukilteo has been certified as a National Wildlife Federation Community Wildlife Habitat.

The group continues their commitment to wildlife by creating and enhancing wildlife habitat in Mukilteo and connecting residents with nature. For more information on the project, go to, contact the group at or 425-514-5979.

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