Beaver Facts
Beaver, the second-largest rodents in the world, are wetland engineers who physically modify the environment more than any other non-human organism in the northern hemisphere. Learn more about beaver benefits, biology, and history below.
Kit catching a ride, photo by Rusty Cohn / Napa Beavers
Beaver Benefits
The dam complexes, bank burrows, and canals beaver build have physical, chemical, and biological effects on the watershed, changing how water flows across the landscape and creating habitat for many rare, threatened, and endangered species.
- Dams on a creek or river can act as a buffer in high flows, reducing intensity of floods.
- Beaver dams slow and redirect flood waters across adjacent lowlands, encouraging riparian vegetation, which also works to accumulate new soils and hold existing soils in place.
- In severely incised or down-cut creeks, beaver dams can help bring the streambed up to its original level, reversing the effects of channel erosion.
- As beaver dams spread water out, creating wetter habitat, they promote subterranean recharge and the release of water later in the season. This can be immensely helpful in California’s Mediterranean climate where we do not receive rain during the hot summer and fall months and are experiencing prolonged droughts.
- Beaver-managed wetlands create important habitat that is less prone to burning during wildfires. These aquatic refuges provide many species with escape cover during fires and intact habitat after the burn.
- One study showed that the beaver dams in Taylor Creek, which empties into the southern end of Lake Tahoe, help keep phosphorus from entering the lake.
- When an oil pipeline broke in northern Utah in 2013, a beaver dam prevented diesel from reaching the fresh waters of Willard Bay.
Dam building keeps the sediment and soils of wetlands hydrated, preventing the carbon from drying out and releasing into the atmosphere. The carbon from the wood beaver use to make their dams is sequestered as well.
- Recent research indicates that many of California’s native and endangered fish, such as coho salmon, steelhead trout, and Lahontan cutthroat trout, benefit greatly from the presence of beaver habitat modifications (dams, wetland complexes, canals, lodges, bank burrows, and submerged stick piles). These modifications provide fish with areas to escape from predators and high flows while providing access to a greater abundance of food sources.
- Unlike human-made dams, beaver dams are not a threat to fish passage.
- Shallow wetlands or “fens” associated with beaver dams provide ideal breeding ground for amphibians, including the Cascades frog, which has been identified as a species of special concern.
- Beaver ponds provide excellent habitat for many different waterfowl and other birds, including the endangered willow flycatcher and least Bell’s vireo.
- As beavers re-inundate critical meadow habitat, encroaching conifers are drowned out and become snags which provide excellent nesting sites for woodpeckers, owls, and other cavity nesters.
- Beaver restoration can be an important tool to reclaim the historic footprint of critically important wet meadows and riparian habitats.
Beaver Biology
Globally, there are two species of beaver, and both are native to the northern hemisphere. The Eurasian beaver (Castor fiber) has a native range that includes much of Europe and Asia. The North American beaver (Castor canadensis) has a range that runs from the taiga in northern Canada to the deserts of northern Mexico, including California. Highly adaptable, the North American beaver has a range that is limited primarily by the availability of water and food.
As adults, these mammals weigh 40—80 pounds.
- Beaver live in tight-knit groups called colonies composed of one mating pair, the young of the year (kits), yearlings, and sub-adults.
- Beaver only have one litter of kits a year.
- By age t or 3, sub-adults disperse to find habitat and establish a new colony, traveling on average 30 miles by water or 12 miles overland.
Beaver live an average of 12 years in the wild.
- Beaver are herbivores.
- They eat a wide range of foods, from the inner bark of deciduous trees to herbaceous matter such as grasses, leaves, bulbs, and rhizomes.
- Beaver front teeth (incisors) continue to grow throughout their lives and will outgrow their skull if not kept sharp by chewing on wood regularly.
- Beaver need aquatic habitat to protect themselves from predators, including mountain lion, wolf, coyote, bobcat, bear, river otter, and human trappers.
- Beaver colonize existing ponds, lakes, streams, and rivers and dig out burrows in banks or build mud-plastered wood lodges above the water line.
- Beavers are highly adaptable. There is no known genetic difference between those who build lodges and those who build dams. Site conditions determine the strategy.
Beaver are often confused with several other animals, including nutria, muskrat, mountain beaver, and river otter. Here’s how they’re different.
Beaver History in California
The North American Beaver (Castor canadensis) is believed to have historically occupied the vast majority of watersheds across California. From the 1700s to the early 1900s, the genocide of indigenous tribes, the decimation of beaver through the fur trade, and other extractive efforts greatly altered watershed function throughout the state. Restoring beaver and supporting our tribal partners in their land-back and restoration goals have proven effective ways to begin healing from these legacy impacts.
There has been confusion about where in California beaver historically lived. Many still refer to analyses conducted in the 1940s that assert beaver were only native to the Central Valley and the Klamath and the Colorado River basins.
The WATER Institute joined efforts with a group of beaver advocates to re-evaluate the historical records and publish peer-reviewed papers summarizing the physical, historical, and ethnographic evidence we found. This evidence suggests that beaver historically ranged across much of the state. The physical evidence includes buried beaver dams in the Sierra Nevada (carbon dated to 530 A.D.) and buried beaver bones in the San Francisco Bay Area and the North Coast of California. Numerous historical accounts from explorers, sea captains, and trappers arriving to the state first by boat and later on foot suggest beaver were found across the state, including in the Sierra Nevada mountains and as far south as San Diego County. Ethnographic evidence includes a word for “beaver” in 60 Native California languages, beaver stories, beaver parts used for ceremonial objects, their bones found in middens, and their distinct image portrayed in the pictographs of Native California tribes. To learn more, see our peer-reviewed published papers.
Humans have utilized beaver for food, pelts, medicine, and fur for millennia. While Europeans were hunting Castor fiber nearly out of existence, Castor canadensis still flourished across the North American continent. Scientists estimate that there were between 60 and 400 million beaver on the continent prior to European colonization. Millions of beaver dams and ponds covered more than 300,000 square miles in pre-Columbian America. A tenth of the total land area was rich, ecologically diverse wetland, creating a mosaic of habitat for insects, amphibians, fish, birds, and mammals.
Most accounts of fur trapping in California begin with the 1826 arrival of mountain man Jedediah Smith, who came in on foot from the east. We have found new evidence that suggests seagoing trappers had already begun to hunt and trade furs on the coast as early as the 1790s. Russian, American, and European fur traders sailed up and down the coast, trapping and trading for whatever furs they could find. It appears, from the historical records, that by the time overland explorers reached California, most of the coastal populations of fur-bearing animals had already been exterminated.
There was no effort to conserve beaver while they were being trapped out of California from the 1780s to the 1850s. Quite the opposite occurred, in fact. Between 1823 and 1841, the Hudson’s Bay Company ordered their employees to create a “fur desert” in the West in order to edge out competing trapping companies. The high demand for fur during this period drew so many people to the West that Dr. Rick Lanman has dubbed this era the “California Fur Rush.” Soon, the Fur Rush gave way to the Gold Rush, and by the early 1900s, there were an estimated 1,000 beaver left in the state.
Beaver trapping laws were mostly unchanged until 2019, when the Wildlife Protection Act outlawed recreational and commercial trapping.
Recognizing the fragile status of beaver, the California Division of Fish and Game (as it was called at the time) passed a law in 1911 to protect the remaining beaver from being killed. Once beaver population numbers started to climb, the law was revised to allow the killing or “depredation” of nuisance beaver by landowners suffering damage to property. Agriculturalists in the California Delta were concerned about beaver “endangering or destroying the levees or other protective works of any reclamation, levee, or swamp-land districts.” Beaver numbers again decreased, and the ban on killing was reinstated. By the mid-1930s, the landowner’s right to seek a depredation permit was restored for a final time and still stands today.
From 1923 until 1950, the California Division of Fish and Game recognized the benefit of beaver dams to soil, water, and wildlife conservation and initiated an extensive translocation program to repopulate the state with this helpful watershed engineer. California Fish and Game biologist Donald Tappe wrote in his 1942 status of beaver report that “it is now understood that soil erosion and shortage of water in some places resulted from the destruction of the beavers which formerly built, and kept in repair, dams on the upper reaches of many streams.” A total of 1,221 beaver were live-trapped and delivered to watersheds across the state and were even dropped from airplanes into the El Dorado National Forest using boxes with parachutes attached! Some of our beaver colonies today descend from those transplanted during translocation programs.
Recent Changes to Beaver Policy in California
From 2019 to 2024, major beaver policy, funding, and narrative changes at the state level have taken place that recognize the conservation value of beaver:
In 2019, recreational and commercial beaver trapping were outlawed with the Wildlife Protection Act.
In 2022, CDFW made significant changes to how they represent beaver on their website, launching a new webpage on International Beaver Day (April 7th) that acknowledges that beaver are native to California and worthy of conservation and provides a comprehensive list of coexistence resources, including OAEC’s beaver stewardship guidebook.
In June 2023, non-lethal beaver management got a significant boost with CDFW’s release of new beaver depredation guidelines. Drafted in response to our petition to the Fish and Game Commission to improve CDFW’s approach, this new guidance ensures that the state will first determine whether or not listed endangered and threatened species will be impacted and require landowners to carry out coexistence methods before issuing a permit to kill “nuisance” beaver.
- In 2023, the Governor approved a budget that included the creation of a new CDFW-led Beaver Restoration Program. This watershed moment ushered in a whole new era of state-supported beaver and process-based restoration.
- In 2024, a Beaver Management Plan will be created in consultation with the Technical Advisory Group and input from the general public.
- CDFW allocated funds from the Nature Based Solutions grant program to cover the cost of beaver damage deterrence.
For specifics on the current state laws and regulations that pertain to beaver, go to the CDFW page.
