Found mostly in the damp forests of the Pacific Northwest, this creature is a “living fossil,” meaning it has changed very little for millions of years. It is considered the most primitive living rodent, with features that set it apart from other members of its order. Unlike true beavers, mountain beavers are much smaller—about the size of a large guinea pig—and lack the famous flat tail. Their fur is soft and dark brown, perfect for blending into the undergrowth, and they are burrowers by nature, creating extensive underground tunnel systems where they spend much of their lives.

One of the most unique characteristics of the mountain beaver is its teeth and jaw structure. They must constantly chew on plants because their teeth grow throughout their lives and because they have a special system for moving food into their cheek pouches while gnawing. This allows them to carry leaves and twigs back to their burrows for later consumption. They are strict vegetarians and are known to nibble on ferns, bark, and shoots. Interestingly, mountain beavers have a high water requirement and must live near moist habitats. In fact, they have the unusual distinction of being unable to concentrate their urine well, which means they need constant access to water and lush vegetation to survive.

Beyond their anatomy, mountain beavers are fascinating for their behaviors and history. For example, they dig elaborate tunnel systems that can stretch many feet underground, with multiple entrances and storage chambers for food. This makes them important “ecosystem engineers,” since their digging helps aerate the soil and influences plant growth. Fossil evidence suggests that their ancestors roamed North America long before many other rodent species existed, which is why scientists sometimes call them a “living window into the past.”

Distribution

Country

Population est.

Status

Year

Comments

Canada

2016

British Columbia

United States

2016

Oregon, California, Washington