Sierra Mountain Beaver


Classification: Rodent
Size: Body length – 13 to 18 ½ inches, Weight – 2 to 3 pounds
Life Span: The lifespan may reach 5 to 6 years



This chunky, grizzled gray rodent looks a lot like a tailless muskrat . It has a small, one inch furred tail. The fur is course and dull, the eyes are small, and the ears are small and rounded.



Mountain beavers inhabit moist forest habitats with ample vegetative ground cover.



Populations of mountain beavers are found in west central Nevada, northern California, western Oregon, western Washington, and southwestern British Colombia.


Natural History:

Mountain beavers make extensive, shallow burrow and tunnel systems in the ground.they are generally solitary ( except during breeding and when the female is raising her young.) Most of their time is spent on or below ground; however, they will also climb trees and swim. Mountain beavers are active throughout the year. Most activity occurs at night but they will be active throughout the day. Periods of activity tend to alternate with periods of rest. Mountain beavers have archaic kidneys and are not able to concentrate urine. They also are unable to sweat or pant so they require a cool regime and water available at all times.


Food Habits:

Mountain beavers are herbivores. They forage mainly on the ground for various types of herbaceous plants , trees and shrubs. Grasses and forbs are dried and stored for winter use. Surface water or succulent vegetation is consumed on a daily basis.



Females are ready to breed at about 2 years of age. An oval nest of leaves, twigs, and grasses is constructed in a chamber located about two feet below the surface of the ground. 2 to 4 young are born in march to April after a gestation period of 28 to 30 days. The young are weaned in about 6 to 8 weeks.



Mountain beavers are state protected in Nevada and are further classified as sensitive.


Fun Facts:

  • The mountain beaver is thought to be the most primitive living rodent.
  • This rodent is the only living member of the aplodontia family and this species is over 40 million years old.