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What is a Mountain Beaver?

Updated on December 16, 2014

The Elusive Mountain Beaver

Mountain Beaver Face
Mountain Beaver Face | Source

Aplodontia rufa, Mysterious Mammal of the Pacific Northwest

Most people have probably never heard of a Mountain Beaver, let alone seen one. The scientific name is Aplodontia rufa, and although the face looks a little like a beaver they aren't even close relatives. Mountain beavers don't necessarily live in the mountains, either. In fact they are more common in lowland forests. They are considered by many scientists to be the most primitive living mammal species on earth and live in a relatively small area of North America in the Pacific Northwest. Although people don't often actually see a mountain beaver, they may often encounter the evidence of their existence.

Many a gardener in the Pacific Northwest has looked out at their garden one morning to find it has been devastated overnight and wondered what the heck happened. They may have had a visit from a mountain beaver. Mountain beavers have a voracious appetite and can make short work of a garden.

Hikers can also be victims from the work of a mountain beaver. The tunnels left by mountain beavers on hiking trails are just the right size for a human foot to slip into resulting in sprained and broken ankles.

Despite living in the Pacific Northwest in an area where I frequently see their tunnel holes, I have never seen a live mountain beaver. On several occasions I have found dead ones on the side of a road or trail and I have seen taxidermy specimens in museums, like the one on display at the Longmire Museum at Mt Rainier.

Despite the damage that is sometimes caused, perhaps getting to know a little bit more about Mountain Beavers will give you an appreciation for these interesting, unique and mysterious little animals.

Mountain Beaver - Real or Myth?

Have You Ever Heard of a Mountain Beaver?

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A Taxidermy Specimen of a Mountain Beaver (Aplodontia rufa)

Mountain Beaver at the Longmire Museum, Mt. Rainier National Park, WA
Mountain Beaver at the Longmire Museum, Mt. Rainier National Park, WA | Source

Where to See a Mountain Beaver

The only place in the world where Mountain Beavers reportedly live is in the Pacific Northwest area of North America. There are 7 different subspecies found between approximately the northern half of California northward into southern British Columbia. They are found mostly west of the coastal mountain ranges, and some subspecies in California are species of concern due to the small population numbers. Where I live in Western Washington, they are seldom seen, but fairly common residents in forested areas.

Where do Mountain Beavers Live?

Range Map of the  Mountain Beaver
Range Map of the Mountain Beaver | Source
Wildlife of the Pacific Northwest: Tracking and Identifying Mammals, Birds, Reptiles, Amphibians, and Invertebrates (A Timber Press Field Guide)
Wildlife of the Pacific Northwest: Tracking and Identifying Mammals, Birds, Reptiles, Amphibians, and Invertebrates (A Timber Press Field Guide)

This is one of my favorite field guides for identifying wildlife in the Pacific Northwest. It has keys to help you identify not only the animals you see, but also signs of their nests and how to identify their tracks and scat.


Learn how to Identify Animals of the Pacific Northwest - Field Guides to Mammals of the Pacific Northwest

If you suspect that you have seen either a mountain beaver or evidence that one is living in your area, these field guides contain a wealth of information about how to identify mammals of the Pacific Northwest, a description of the habitat where they are found and other information that is known about their life cycle.

Evidence of Mountain Beavers

Since mountain beavers are primarily nocturnal, the holes in the ground that lead to their underground burrows may be the only evidence that indicates they are living in the area. I took this photo in a forested ravine near a creek in my neighborhood. It is pretty typical of a mountain beaver burrow. As you can see from this one, the entrances to the tunnels are often on a slope or hillside that is covered with vegetation and there is dirt fanned out around the entrance. There may also be freshly cut vegetation they've recently harvested near the opening of their tunnel. They usually live near a pond or creek because they need to drink 20% to 30% of their body weight in water daily because of their inefficient kidneys.

Mountain Beaver Habitat and Signs

A Mountain Beaver Burrow
A Mountain Beaver Burrow | Source

Mountain Beaver Tunnel Entrance

Mountain Beaver Tunnel
Mountain Beaver Tunnel | Source

A Typical Mountain Beaver Home

The typical opening to a Mountain Beaver burrow is between 6 to 8 inches in diameter. The above photo doesn't show it very well, but there were several small evergreen tree needles and twigs and other plant debris around the entrance. The holes are often partially or even totally hidden by vegetation so they can be a hazard for hikers.

Aplodontia Rufa makes an extensive tunnel system, reported to sometimes be as deep as 10 feet underground with 10 or more entrances. They have separate chambers in their burrows for food storage, feeding, nesting and toilet area. The territory of an individual mountain beaver may be 2 acres or more, depending on the food supply in the area.

The mountain beaver is important to other creatures in the forest because their abandoned tunnels are used by several other species including rabbits, minks, skunks, mice, salamanders, moles, voles, weasels and rats.

Front Claws of an Aplondontia Rufa

Mountain Beaver Front Claws
Mountain Beaver Front Claws | Source

Mountain Beavers are Equipped for Digging

The mountain beaver has extremely long sharp claws on both front and back feet that are well suited for digging. No wonder they are capable of making so many tunnels and holes! The photos above and below were taken of an unfortunate mountain beaver that I found dead along the side of a trail.

Mountain Beavers are Equipped for Eating - Aplondontia rufus Teeth

Mountain Beaver Teeth
Mountain Beaver Teeth

My What Big Teeth You Have!

If you've ever seen a mountain beaver's set of choppers, it is easy to understand how they are able to decimate a garden overnight. Although not an animal that is usually aggressive, it will defend its territory and if cornered or grabbed, those teeth can inflict a nasty bite.

Salmonberry - A Pacific Northwest Shrub

Salmonberry | Source

What do Mountain Beavers Eat?

Mountain beavers are herbivores, so they eat only plants. Some of the native plant species that they eat include salal, ferns, fireweed, bleeding heart, nettles, dogwood, currants, vine maples, willows, alders, evergreen trees, salmonberry and other rubus species.

However, they are perfectly happy to dine on plants growing in gardens like rhododendrons, trees, shrubs, flowers and even vegetables.

They may eat the plants immediately or they may briefly store them outside their tunnel entrances before taking them to food storage chambers inside their underground nests.

What does the Mysterious Mountain Beaver Look Like?

Apodontia rufa
Apodontia rufa | Source

A Description of a Mountain Beaver

Those who have seen the elusive mountain beaver have variously described it as resembling a tail-less muskrat, woodchuck, gopher, a large mole or a giant hamster. They are in a very primitive family of rodents all by themselves. Their closest relatives are squirrels. They are brown and gray in color and are round and bulky looking. The average weigh of a full grown mountain beaver is about 1-2 pounds (900 g) and average overall length about 12 to 13.5 inches (34 cm), including a short tail about 1 inch (2.5 cm) long. They have tiny eyes, small ears and long silver whiskers. This specimen photographed in a museum looks a lot lighter in color than the dead ones I've seen.

A Young Mountain Beaver

Immature Mountain Beaver
Immature Mountain Beaver | Source

Life Cycle of the Mountain Beaver

Compared to most other mammals in the Pacific Northwest, research and information about mountain beavers is relatively sparse so many of the details about their life is still a mystery.

What is known is that mountain beavers don't live in colonies like some rodents. They are solitary except for during mating season and they have a home territory they will defend from from other mountain beavers or other species. Female mountain beavers do not reproduce until they are about two years old and they only have one litter of young per year. Depending on where they live, they breed sometime between December and April and if all goes well, 2-4 baby mountain beavers are born 28 to 30 days later. The babies nurse for up to 60 days.

They aren't known to hibernate so they are active year-round. They are either mostly nocturnal or, if they are awake during the day, must spend most of the daylight hours underground in their burrows.

Like most rodents, they are near the bottom of the food chain and their main predators include coyotes, bobcats, minks, weasels and owls and, of course, domestic cats and dogs. No one has done much research about how long mountain beavers live, but it is estimated that their maximum life expectancy is about 6 years.

Watch a Video About Mountain Beavers

Skeleton of a Mountain Beaver - Aplondontia Rufa Bones

Mountain Beaver Skeleton
Mountain Beaver Skeleton | Source

A Mountain Beaver at the Smithsonian Museum

Lewis and Clark encountered mountain beavers during their expedition to the Pacific Northwest and described them in their journal. The above photo of a mountain beaver skeleton was taken at the Smithsonian Museum of Natural History. Mountain beavers are considered to be the most ancient, primitive rodent still living on earth. There is archealogical evidence that their species has lived in the Pacific Northwest, virtually unchanged, for over 40,000 years.

Mountain Beaver Trivia

Scientific Name: Aplodontia Rufa

Food: Plants (herbivore)

Weight: 1-2 pounds

Length: 12-14 inches

Color: Brown and/or Gray

Life Span: 5-6 years

Reproduce at 2 years of age

Females have 2-3 young every spring

Mostly Nocturnal

Can climb trees

An Injured Mountain Beaver Being Treated

Protect Your Trees from Damage

Tree Bark Protectors
Tree Bark Protectors | Source

How to reduce or eliminate Mountain Beaver Damage

What to do if a Mountain Beaver Becomes a Pest

I must confess, I'm biased. I enjoy having wildlife in my yard and will do my best to make accommodations to be able to co-exist with them. Especially in the case of a primitive species like a mountain beaver, I always keep in mind that their species was living on this land before mine, so they have as much right, if not more, to be here.

Some ideas from the experts for minimizing damage from mountain beavers include protecting trees by installing a barrier around the trunk.

More Ideas for Minimizing Mountain Beaver Damage

1. Fencing that extends several inches below ground level to create a barrier to discourage them

2. Use plant tubes on seedlings, shrubs and small trees to protect them

3. Plant new shrubs, trees and gardens as far away from their dens as possible

4. Install a squirrel baffle, metal collar or predator guard on trees they are climbing

It has been reported that moth balls, castor oil and clothes dryer sheets do NOT repel them

Havahart Live Traps

Havahart 1030 Live Animal Two-Door Rabbit, Squirrel, Skunk, and Mink Cage Trap
Havahart 1030 Live Animal Two-Door Rabbit, Squirrel, Skunk, and Mink Cage Trap

If you want to trap and relocate a mountain beaver or any animal of a similar size, a Havahart trap will help you catch them safely and without injury to you or the animal.


What About Trapping and Relocating Mountain Beavers?

Since mountain beavers are solitary except during mating season and while mothers are raising their young, live trapping and relocating may help at least temporarily. But eventually if the area has suitable habitat, another mountain beaver will probably eventually claim the territory as its own. In some areas it may be illegal to trap and transport wild animals, so be sure to check the laws in your area.

Attract Barn Owls With a Nesting Box

JCs Wildlife Barn Owl Nesting Box Large House Crafted in USA w
JCs Wildlife Barn Owl Nesting Box Large House Crafted in USA w

If you have a problem with an over abundance of mountain beavers or any other rodent, this barn owl nesting box may help to encourage a family of owls to live in your yard. This box is well constructed and has all of the features that will help a pair of owls safely raise their family.


Limit Mountain Beaver Damage By Attracting Owls

The last thing to try before resorting to lethal methods yourself, is to make an effort to increase the number of natural predators in your area. Make the habitat in your yard as suitable as possible for predators of mountain beavers like bobcats, fishers, coyotes, owls, skunks, eagles, and minks. Owls would probably make the best neighbor since they are most active at night,like the mountain beaver and have fewer habits that humans find objectionable. They one of the easiest predators to attract by placing owl nesting boxes in trees and other suitable places.

Living with Wildlife in the Pacific Northwest

Living with Wildlife in the Pacific Northwest
Living with Wildlife in the Pacific Northwest

Russell Link offers many ideas about how to enjoy and peacefully co-exist with our Pacific Northwest wildlife.


Co-Existing with Native Wildlife in the Pacific Northwest

If you are looking for more information about mountain beavers and other wildlife in the Pacific Northwest, you may want to add this book to your library. Written by Russell Link, an urban wildlife biologist with the Washington State Department of Fish and Wildlife, it has tips for attracting and enjoying wildlife while preventing potential problems and conflicts.

© 2013 Vicki Green

Please sign my guestbook - Feel free to share your experiences about mountain beavers

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    • Old Navy Guy profile image

      Old Navy Guy 

      5 years ago

      More akin to the common mole I think. Thanks for sharing the picture of a dead one, as for many, they have never seen one up close.

    • PNWtravels profile imageAUTHOR

      Vicki Green 

      5 years ago from Wandering the Pacific Northwest USA

      @MarcellaCarlton: I love finding kindred spirits! I know it sounds morbid, but I've often taken photos of deceased animals that I find. I also sometimes take dead animals and birds that I find to a local university natural history museum that is interested in having the specimens. Often the deceased spend some time in my freezer to keep them fresh them until I can arrange to deliver them to the museum. One time my wonderful, tolerant husband was unpleasantly surprised when he reached into the freezer and his arm was slashed by the sharp talons of a dead Cooper's hawk I had found in our backyard.

    • profile image


      5 years ago

      Love this lens on the mountain beaver! Vicki only you or I would find one of these dead and start taking pictures. I've never seen one so far, but will some day. And because of you I will know what it is.

    • skhdesigns lm profile image

      skhdesigns lm 

      5 years ago

      Cool! Maybe (if I am extremely lucky) I'll see one someday in the California mountains. In one way they look a little like Picas.

    • profile image


      5 years ago

      his teeth are so funny :)

    • profile image


      5 years ago

      his teeth are so funny :)

    • profile image


      5 years ago

      We heard about the mountain beaver in Abbotsford, BC, Canada. I've never seen one but know of people who have, mostly on one mountain. People are fighting to save them but it's difficult due to their timidity; property owners want to sell their land for development.

    • KatsLife LM profile image

      KatsLife LM 

      5 years ago

      I used to be a forester in Oregon, and mountain beavers ARE real! They love to nibble newly planted seedlings and young conifers! Mmmm.... conifers...

    • greenmind profile image

      GreenMind Guides 

      5 years ago from USA

      Huh. Never heard of this animal. Either an amazing new thing to learn or a REALLY impressive hoax...

    • IMKZRNU2 profile image


      5 years ago from Pacific Northwest

      All of my years spent hiking in the woods and we have never seen one of these creatures. I learned a lot from your lens! Thanks!

    • profile image


      6 years ago

      Wonderfully informative Lens. These guys remind me of our groundhogs. Though your mountain beaver does have the edge on the claws.

    • profile image


      6 years ago

      Lots of good information and well researched. I enjoyed your lens and photos.

    • profile image


      6 years ago

      I learned a lot about Mountain Beavers today. Thank you for sharing this wonderful lens!

    • suepogson profile image


      6 years ago

      Lovely to learn about an animal I didn't know. Thank you.

    • safereview profile image


      6 years ago from Kansas City

      What a great lens! I really enjoyed this, many thanks for sharing it.

    • sbaiju profile image


      6 years ago

      Great article you have done your homework on beaver

    • Diana Wenzel profile image

      Renaissance Woman 

      6 years ago from Colorado

      I found this article very interesting. I was unaware of the mountain beaver. Thanks for expanding my horizons. Always appreciated. Hope I get to see one of these primitive creatures (alive) at some point in my lifetime.

    • makorip lm profile image

      makorip lm 

      6 years ago

      Also live near Seattle. No mountain beavers but raccoons. Very informative lens!


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