January 2025  by Ranger Jay Manning

Introduction to Beavers 

Beavers (Castor canadensis) are the second largest rodents in North America. Beavers are crepuscular. The term crepuscular refers to animals that are most active during dawn and dusk. Beavers have a stocky build, and adults can weigh anywhere from 35 to 65 pounds. Their front teeth are coated in iron which allows them to gnaw down trees. Beavers are often identifiable by their unique large, flat tail which is used like a rudder while beavers are swimming and helps beavers balance when they are on land. Beavers may also use their tails to signal danger by slapping them on the water.

It is a common misconception that beavers live in the dams they build; however, this is not true. Beavers live in a structure called a lodge. They build these lodges by using their front paws to move sticks and dig up mud to create a hut-shaped structure. Beaver lodges have an underwater entrance to protect beavers from predators such as eagles, coyotes, and other large mammals. The dams beavers build create pools of water allow them to build an underwater entrance to their lodge and dig canals to safely transport food.  

Close to Extinction 

Beavers are native to northern California, but in the 1800s, were almost hunted to extinction when their furs were highly sought after by fur traders in the Bay Area. Beavers were also viewed as nuisance animals and killed due to the impact their dams had on landscapes.  As beaver populations dropped all over North America, settlers moving west were cutting down forests, changing the path of waterways, draining wetlands, and leveeing floodplains to use the nutrient-rich soil for farming. By 1912, it was estimated there were fewer than one thousand beavers in California.  

Impactful Animals  

Beavers are a keystone species, a term used to describe species that have an extremely significant impact on the ecosystem relative to their population. Beavers have also been called ecosystem engineers because their dams change the structure of entire ecosystems. When beavers build dams, they can reshape rivers and streams, increase riparian (wetland) habitats, alter stream temperatures, filter streams, and increase groundwater storage.  

The physical impacts created by beavers and their dams are also linked to increased biodiversity in their ecosystems. Many animals benefit from the presence of beavers. Deer and other herbivores eat twigs from trees felled by beavers and the new growth that comes because of ‘beaver ponds’ (a body of water created when a beaver builds a dam). Increased light exposure due to beavers felling trees helps the growth of algae in beaver ponds. Fish populations benefit from the food and cover provided by algae and other aquatic plants.

In addition, amphibians, like the threatened California red-legged frog and endangered California tiger salamander, rely on wetland habitats. 90% of wetlands in California were destroyed by humans, but some of these wetland habitats can be recreated by beavers.

Although the importance of beavers in an ecosystem was not initially recognized or appreciated, in the mid-1900s, restoring and protecting beaver populations began to gain popularity among environmental agencies.  

No Longer a Nuisance 

In the 1940s, environmentalists began to see the negative impacts of beaver population decline. Ground water levels fell throughout North America leading to a less diverse and drier environment. The goal became to reduce future damage. The perspective of beavers began to shift from a nuisance animal, to one that was critical for the health of an ecosystem. However, still, beavers are not the best neighbors and were causing flooding on people’s property.

To reduce human-beaver conflicts, beavers were trapped in urban areas then brought by car and/or horseback to more rural areas. This process was long and stressful for the beavers, so there was a high mortality rate throughout this journey. To reduce the beaver mortality rate during relocation, a new method was developed. Starting with the Idaho Department of Fish and Game in 1949, they began to drop beavers into more remote wetlands from planes using leftover parachutes from World War II. This practice was soon followed by the California Division of Fish and Game (now California Department of Fish and Wildlife). The agency dropped beavers into the El Dorado National Forest. After the beavers landed their instincts would help them locate the water. This method was successful and had a much lower mortality rate.  

Work in Progress 

In the 1980s, the California Division of Fish and Game began another effort to restore beaver populations, although this effort did not involve parachuting beavers. In this effort, the California Division of Fish and Game brought beavers to the Lexington Reservoir and upper Los Gatos Creek. In the four decades since, beavers have expanded their range on both sides of the bay with sightings in Los Gatos Creek, Guadalupe River, Coyote Creek, Palo Alto, Martinez, and Walnut Creek. In 2022, two beavers were seen in Matadero Creek in Palo Alto. This pair is believed to be related to the original beavers brought in the 1980s. Increased beaver sightings in the Bay Area are a welcome sight to experts who believe increased sightings are linked to higher beaver populations.  

As California residents, we should also be excited about increasing beaver populations. Due to climate change, precipitation is occurring more often as rain than snow, therefore there has and will continue to be less snowpack in the Sierra. The Sierra snowpack is the source of about one-third of the state’s water. As snowpack decreases, groundwater storage from rain is a key factor to create current and future drought resiliency. Beavers can aid drought resiliency because they create more riparian habitats. These riparian habitats have more ground water storage and faster water recharge. Additionally, riparian habitats provide a natural firebreak which has become more important as the frequency of fires is increasing due to climate change.  

Beaver population restoration could be vital to transform some of our ecosystems from dry, fire-prone areas to thriving, biodiverse landscapes and to help ensure water security in California’s future.

So, next time you see a beaver, remember all the hard work they are doing that benefits the natural environment and the people of California!