Beaver

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 tail
• 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.

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.
• 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.

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.

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.

Beavers are attracted to the sound of running water and will seek to plug most culverts or pipes with the goal of creating more or maintaining pond habitat. Additionally, beavers will repair most dam breaches and plug most culverts and pipes that are installed in order to drain the ponds. However, a variety of devices have been developed for controlling beaver impoundments and keeping blocked culverts open. These deterrents (also referred to as coexistence devices) allow landowners to control the water level in beaver ponds, minimize or eliminate the running water sound that triggers their instinct to plug and repair, and mitigate beaver damming efforts without the beavers being aware of their presence. Learn more about three of these devices:

• Beaver Deceivers LLC
• Flexible Pond Levelers | Beaver Solutions
• Beaver Back Saver
  • OAEC Device Summary (PDF)
  • OAEC Installation Video
  • OAEC How-To Details

• Living With Beavers (PDF)
• Beaver Damage Management (PDF) (USDA)
• Resolve Beaver Conflicts (PDF) (MDIFW)
• Beaver Restoration Guidebook (PDF) (Interagency)
• Beaver Damage Prevention and Control Methods (PDF) (UNL)
• Best Management Practices for Pond Levelers and Culvert Protection Systems (PDF) (The Beaver Coalition)