Beaver

Beaver mother and kits
Beaver lodge, Sac-San Joaquin Delta
Beaver swimming in water
Beaver dam at GCWA

Introduction

The North American Beaver (Castor canadensis) is native to California and considered a "keystone species”. They are ecosystem engineers helping to create and maintain diverse habitat throughout the State. The California Department of Fish and Wildlife strives to partner with native tribes, non-governmental organizations, private landowners, and other state and federal agencies to successfully implement restoration projects statewide that support beaver conservation.

Conservation and Management

The Department supports a comprehensive approach to beaver management in California that is responsive to conservation needs and reported human-beaver conflict, such as property damage (depredation). The conservation and management of this keystone species is supported through the implementation of various nature-based solutions. The Department also strive to provide funding to partners in conservation conducting restoration projects that can benefit the beaver.

Historically, beavers used to live in nearly every stream in North America with an estimated population of 100-200 million. Human exploitation and eradication efforts reduced those populations to approximately 10-15 million beavers today. Learn more!

Science and Research

CDFW continues working to better understand the complex conservation needs of the beaver, a keystone native species. Research is vital to applying an adaptive approach to managing their population in California.

Beaver Biology

Appearance

Beavers (Castor Canadensis) are the largest rodent species in North America. They have thick bodies and large heads with brown fur. Adults weigh up to 40 pounds and measure more than 3 feet in length including tail. Beavers are the only species known to create their own habitat, and have evolved perfectly suited for their environment. 

  • Wide flat scaly tailBrown beaver standing still
  • Webbed back feet
  • Nimble hand-like front feet
  • Long chisel-like incisor teeth
  • Thick, water-proof fur

Diet

Beavers are strict herbivores and they generally prefer grasses, leaves, and aquatic plants such as cattails, bulrushes, and water lilies. In the fall and winter, they feed primarily on the bark and cambium of shrubs and trees such as aspen, cottonwood, willow and alder. Beavers sometimes consume agricultural crops, and in some cases may travel 100 yards or more from a body of water to reach corn fields, soybean fields, and other crops. In these cases, they generally cut the plants off at ground level and drag them back to the water.

Reproduction

Beavers are monogamous and mate for life. Females reach sexual maturity at 1.5 to 3 years of age and will typically birth 1-4 or more kits per year, depending on habitat quality and food availability. Beavers typically breed only once a year during the winter months. Females give birth to kits in late spring (Baker and Hill 2003).

Beavers live in family units consisting of one adult breeding pair, their young of the year, and young from the previous year. Offspring may remain with the family unit for more than 2 years if habitat quality is poor or population levels reach carrying capacity.

Beaver Behavior

Beavers are generally nocturnal. However, it is not uncommon to see them during the day in larger water bodies. Beavers generally avoid people and do not stray far from the relative safety of water.

  • Beavers need water deep enough to swim to their food sources and avoid predators. beaver grooming tail
  • They build dams and lodges of woody material, dig canals and plug culverts to increase the depth and area of suitable habitat.
  • This woody material is gathered from the ground locally or from small and medium-sized trees that the beavers fell with their specialized teeth.

Beavers do not hibernate. When the water surface freezes in the winter, beavers eat bark and stems from a food “cache” they have anchored to the bottom of the waterway for the winter. They will also swim under the ice to retrieve roots and stems of aquatic plants.

Habitat and Range

Beavers were once one of the most widely distributed mammals in North America. However, beavers were eliminated from much of their range due to unregulated trapping and habitat loss by the late 1800s.

Beavers are commonly known for their ability to build dams and change waterways – but the ecosystem benefits provided to other native species in the process may be less recognized. Through the process of ecosystem engineering, beavers can expand wetland, riparian, and wet meadow habitats and increase wildfire resiliency in areas with known beaver activity. Specifically, beavers can:

  • Improve water quality and control water downstream
  • Repair eroded channels
  • Reconnect streams to their floodplains
  • Provide perennial flow to streams that would otherwise run dry 
  • Create beneficial habitats as refugia to drought, wildfire, and climate change

In areas with known beaver activity, there can also be significant increase in biodiversity. Deer and elk frequent beaver ponds to forage on shrubby plants that grow where beavers cut down trees. Weasels, raccoons, and heron hunt frogs and other prey along the marshy edges of beaver ponds. Sensitive species such as Red-legged, Yellow-legged and Cascade frogs, Sage Grouse, and Willow Flycatchers benefit from habitat created by beaver wetlands. In coastal rivers and streams, Coho salmon can benefit from beaver dams by finding protection from high flows and predators until they are big enough to go out to sea.

Potential Conflict and Depredation

While the ecosystem services provided by beavers are increasingly valued in California, beavers can cause problems or damage to property at times. There are proven effective exclusion methods to mitigate human-beaver conflict and prevent damage due to beaver activity. For more information, visit the Human-Wildlife Conflict Program page.

Protecting Trees and PlantsProtective fencing, Beaver Institute

Permanent exclusion and/or deterrents can be effective if selectively deployed to protect trees and shrubs, garden plots or agricultural crops.

  • Install low fence (3 feet) constructed of woven or welded wire mesh. Fence should be well-anchored to the ground, so that beavers do not crush, crawl under, or walk over it.
  • Install electric wire 4-6” above the ground.
  • Encircle tree trunks with hardware cloth, sheet metal, or welded wire mesh (2” x 4”).
  • Paint tree trunks with a sand and paint mixture to prevent beaver gnawing. Sand/paint ratio should be approximately 8 ounces (2/3 cup) of fine sand to one quart exterior latex paint.

Preventing FloodingInstall flow device, beaver deceiver

Beavers will repair most dam breaches and plug most culverts and pipes that are installed in order to drain the ponds. They are attracted to the sound of running water A variety of devices have been developed for controlling beaver impoundments and keeping blocked culverts open. Learn more about two of these devices:

Laws and Regulations

Beavers are classified as a furbearing mammal in California. Below are some, but not all Fish and Game Code (FGC) laws and Title 14 California Code of Regulations (CCR) related to beavers.

  • FGC § 4000-4011. Trapping Provisions. Trapping conditions and license requirements. It is unlawful for any person to trap any fur-bearing mammal for purposes of recreation or commerce in fur.
  • FGC § 4181. Depredators. Any owner or tenant of property being damaged or destroyed or in danger of being damaged or destroyed by certain species may apply for a permit to take the animal(s). The Department encourages the use of nonlethal deterrents and permanent exclusion methods as a more effective, long-term approach to preventing damage.
  • FGC § 1602. Fish and Wildlife Protection and Conservation. Any person, state or local governmental agency, or public utility must notify CDFW prior to beginning any activity that may divert or obstruct the natural flow of any river, stream, or lake; or change the bed, channel, or bank of any river, stream, or lake.
    • CDFW requires a Lake and Streambed Alteration (LSA) Agreement when a project activity may substantially adversely affect fish and wildlife resources.
    • Modification of a beaver dam or lodge may require a LSA Agreement. Contact your CDFW local office before installing any beaver devices.
  • CCR § 401. Issuance of Permit to Take Animals Causing Damage. Elk, bear, bobcat, beaver, wild pig, deer, wild turkey, gray squirrels. No animals killed pursuant to such a permit may be utilized by the permittee or their agent.
  • CCR § 463. Beaver. Beaver may be taken only as follows pursuant to this section: Season and Area, Bag and Possession Limit.