Not a true beaver — a primitive rodent in its own family. Among the most evolutionarily isolated North American mammals.

Also called: Sewellel, Boomer, Showt'l (Chinook), Aplodontia

Native status: Native; Pacific Northwest endemic

§ Quick facts

SizeBody 30–47 cm (12–18.5 in); tail vestigial (1–3 cm)
Weight0.9–1.4 kg (2–3 lb)
LifespanWild 5–10 years
OrderRodentia
FamilyAplodontiidae

§ Encyclopedia

The mountain beaver is a North American rodent. It is the only living member of its genus, Aplodontia, and family, Aplodontiidae. It should not be confused with true North American and Eurasian beavers, to which it is not closely related; the mountain beaver is instead more closely related to squirrels. There are seven subspecies of mountain beaver, six of which are found in California and three of which are endemic to the state.

Source: Wikipedia — Mountain beaver Licensed under CC BY-SA 4.0

§ Identification

Field marks. Stout reddish-brown rodent with small eyes, small ears, no apparent tail. Looks like an oversized vole.

Similar species. Beaver (much larger, paddle tail, aquatic). Marmots (much larger, mountain habitat). Pocket gophers (much smaller).

Voice. Whistles, grinding teeth when threatened.

§ Diet & behavior

Diet. Sword fern, salal, vine maple, salmonberry — herbaceous and woody plants. Eats own droppings (cecotrophy) to extract additional nutrients.

Behavior. Not actually a beaver — sole living member of family Aplodontiidae, with no close living relatives. Lineage dates to the Eocene (~50 million years ago) — sometimes called a "living fossil." Lives in complex underground burrow systems with dedicated chambers for sleeping, food storage, and waste. Restricted to cool, moist Pacific Northwest forests; among the most habitat-specific US mammals.

§ Range

Pacific Northwest

§ Habitat

Cool moist coniferous forests

§ Threats

Pacific Northwest forest loss, climate change.

§ Conservation status

According to the IUCN Red List, the american mountain beaver is currently classified as Least Concern.

§ What helps

Support Pacific Northwest forest conservation.

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§ Further reading

§ Sources cited

  • Oregon Department of Fish and Wildlife
  • American Society of Mammalogists
  • IUCN Red List 2016