In 2022, a pair of beavers appeared in the Palo Alto Baylands, the first sighting in over 160 years! Then, last year a pup was spotted as well. They have also popped up in Los Gatos Creek and the Guadalupe River. This is exciting news for environmentalists and the public alike.

Ecosystem Engineers

Beavers are the largest rodents in North America, second in size only to South America’s capybaras. They don’t just live in an ecosystem, they actively change it, which has massive positive impacts for other animals and the land itself. They have even been called ecosystem engineers in acknowledgement of all the work they do. In fact, land managers and restoration ecologists increasingly see beavers as effective partners—and best of all, they work for free!

When these furry builders move in, they use willow trees—also their favorite food—to construct watertight dams. This causes ponds to form, which in turn create a perfect environment for growing more willow trees. These ponds not only protect the beavers from predators who don’t swim, they slow the water, giving more of it time to be absorbed into the ground, raising the level of the water table as well as protecting against fire. This creates habitat for animals including endangered salmon and migratory birds traveling on the Pacific Flyway

Just by being themselves, beavers reconnect streams to floodplains, create new wetlands and improve water quality by keeping sediment in streams. Because of this, they are considered a keystone species vital to their habitats.

Beaver 4-1-1

Beavers are crepuscular, meaning they are most active at dawn and dusk. At three to four feet long, adults usually weigh between 35 and 65 pounds. They can swim six miles per hour and stay submerged for fifteen minutes. Their short, stocky bodies have waterproof fur and their famous flat tails are used as a rudder when swimming, help them balance while working on land and are slapped on the water to signal danger. Their front paws allow them to swim and walk on land as well as to grab sticks and dig—all talents they need for constructing their dams and lodge homes, made of sticks, reeds, twigs and saplings, held together with mud. The lodges have an underwater entrance for protection from predators including eagles, wolves and other large mammals.

Nature’s Lumberjacks

Their two long, self-sharpening front teeth are covered with an orange protective coating that allows them to gnaw down trees. Of course, cutting trees and making ponds sometimes makes beavers difficult neighbors, and previously the solution was to kill them. However, in California it is now illegal to trap any fur bearing animal. If land is being destroyed, or in danger of it, the Department of Fish and Wildlife encourages non-lethal options including painting the bottoms of trees with paint mixed with sand; “beaver deceivers,” which control the level of water behind their dams; or, in extreme circumstances, relocation.

A beaver family swims together
This adult beaver swims closely with their kits, exhibiting family-oriented behavior.

Beaver Families

One of beavers’ most endearing characteristics is a strong family bond. They mate for life and a family group will be comprised of about eight individuals: a breeding pair, one or more members of the previous year’s litter (yearlings), the current kits (babies) and often some two-year-old offspring. They even exhibit a dog pile” behavior with one or more kits riding on the back of an older family member, which can make it look like the kits are surfing.

Decimation of the Population

Historically, up to 400 million beavers lived throughout North America and they figure prominently in the culture of Native Americans. In the late 1700s, having decimated the beavers in Europe, trappers looked to the Americas for animals to use for beaver hats and coats (it took 1–5 pelts for a hat and 10–13 for a full length coat). Estimates are that by 1912 there were fewer than a thousand beavers in all of California. After staging an amazing comeback, they currently number about 10–15 million nationwide.

A New Start in Native Habitats

It took time, but finally, people recognized the value of these hard-working creatures and began reintroducing them into their native habitats. In the 1940s there was even an experiment with parachuting beavers into remote environments!

In 1980, in a similar non-airborne project, the California Department of Fish and Game transplanted beavers to Lexington Reservoir and upper Los Gatos Creek. They thrived in their new environment, with some migrating to the Guadalupe River in San José and Matadero Creek in Palo Alto, where they surprised onlookers when they appeared in 2022.

As scientists realize the immense good these adorable animals can afford an ecosystem, entire families are relocated into suitable habitats and the beavers do the rest. They not only help restore floodplains and wetlands, their young migrate along waterways to establish their own homes, increasing their reach and delighting hikers who are lucky enough to spot one.

Rodents Worth Knowing

Clearly, beavers have a fascinating and complex history, and we look forward to seeing their comeback story unfold. Their return to the Bay Area demonstrates how resilient they are. What’s more, they play a crucial role in our ecosystems, enriching local habitats, protecting us from fire and flooding and fostering biodiversity. Does anyone want to start a beaver fan club?

BONUS: More Fun Facts!

  • Beavers’ hind feet have a “preening toe” with a double toenail, which they use to keep their fur from matting.
  • Their tails store enough fat that they can survive on it through the winter if necessary.
  • The largest beaver on record weighed 110 pounds!
  • They produce oil that waterproofs their fur, marks territory and is a form of communication.
  • While swimming, folds of skin close off their ears and nostrils and a membrane protects their eyes.
  • The largest known beaver dam is half a mile long and has created a 17-acre lake!


About Post

Peninsula Open Space Trust (POST) protects open space on the Peninsula and in the South Bay for the benefit of all. Since its founding in 1977, POST has been responsible for saving more than 87,000 acres as permanently protected land in San Mateo, Santa Clara and Santa Cruz counties. Learn more

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