Test your knowledge with this ‘True or False’ quiz on Mountain beavers (answers follow):

  1. Fur trappers nearly wiped out Northwest boomer populations.
  2. Boomers are closely related to North American and Eurasian beavers.
  3. Boomers or “mountain beavers” are related to squirrels and will climb trees.
  4. Boomers must drink one-third of their body weight each day.
  5. All beavers fall trees, build dams, and live in lodges.
  6. Mountain beavers communicate via tail slaps, which is why they are called ‘Boomers.’
  7. The largest flea known lives exclusively on Mountain beavers.
  8. Boomers have unique teeth.  
  9. Boomers are asocial most of the time.
  10. These rodents live in deep burrows.
  11. Boomers have limited ability to see and hear.
Young Mountain beaver
(courtesy NPS and USGS)


  1. False. Trappers nearly wiped out the American beaver populations, (not the Mountain beaver).
  2. False. Mountain beavers are not even in the same genus with real beavers (genus Castor). The Mountains do have several similarities in that they are relatively large rodents, smell bad, and have brownish-grey fur. This compact rodent weighs less than 2 pounds.
  3. True. Molecular results consistently identify a ‘sister’ relationship between the mountain beavers and the squirrel family (Sciuridae). Mountain beavers have large, curved front claws perfect for climbing, will climb nearly 15 feet up a tree to forage.
  4. True. These mammals are considered to be a living fossil with primitive, inefficient kidneys. They must drink a lot of water to survive. They live in watery/moist habitats up to the tree line in areas ranging from British Columbia south through to extreme western Nevada.
  5. False. Mountain beavers are strictly herbivorous and do not build dams or lodges, or have much of a tail to slap. Typically food includes ferns, salal, nettles, fireweed, bleeding heart, salmonberry, brambles, rhododendron, and young tree saplings.  
  6. False. Slap a less than 2-inch tail? Ouch. American beavers have a large flat tail that they slap to make noise.
  7. True. Hystrichopsylla schefferi is one of the oldest fleas in evolutionary history and females can be up to .5 inches long. Fortunately, the flea only likes Mountain beavers.
  8. True. Mountain beavers have unusual tooth projections and simple form. They are ever-growing.
  9. True. This rodent is not social…except to breed. They stick very close to their home burrow at all times.
  10. True. They create tunnel networks to store food, raise young, and avoid predators. Predators include cougars, owls, skunks, weasels, and domestic dogs. Tunnels can include ten or more exits.
  11. True. Limited sight and hearing is common for animals that spend a lot of time underground.

A few surprises?

Boomers, or “Mountain beavers”, would have a tough time living up to the merits of the well-loved American beaver.

These animals can become a nuisance

If they are a problem, contact the Oregon Dept. of Fish and Wildlife for regulations and relocation options.

–Oregon Dept. of Fish and Wildlife, beavers (https://myodfw.com/wildlife-viewing/species/beavers)
–Washington Dept. of Fish and Wildlife, Aplodontia-rufa (https://wdfw.wa.gov/species-habitats/species/aplodontia-rufa#living)
–Encylopedia Britannica, Mountain beaver (https://www.britannica.com/animal/mountain-beaver)
–USDI National Park Service, Mountain beaver (https://www.nps.gov/pore/learn/nature/mountain_beaver.htm)
–Wikipedia, hystrichopsylla schefferi and Mountain beaver (https://en.wikipedia.org/wiki/…)