Types of Beavers in Washington

American Beavers are stocky, robust rodents weighing 30 to 65 pounds, with a body length of 24 to 35 inches plus a distinctive flat tail that can add another 10 to 15 inches. Their fur is thick, waterproof, and typically brown to dark reddish-brown, with dense underfur beneath coarser guard hairs. The head is broad and blunt with small rounded ears, small dark eyes positioned high on the skull, and prominent orange-yellow incisor teeth that are always growing. Look for the characteristically flat, scale-covered tail that resembles a paddle.

Beavers differ from muskrats by size, habitat, and behavior. A beaver is much larger (30 to 65 pounds versus 1 to 4 pounds for a muskrat) and has a wide flat tail, while muskrats have thin, vertically compressed tails. Beavers construct large stick dams and lodges in rivers and streams, whereas muskrats dig burrows in banks. Otters, another common aquatic animal in Washington, are sleeker, faster swimmers with slimmer tails and smaller heads. Nutrias, an introduced rodent, are similar in size to muskrats and lack the distinctive flat tail. Beavers are also active year-round; they do not hibernate.

Beavers leave obvious marks in their habitat. Look for freshly cut trees with chiseled stumps, sometimes topped with pencil-sharp points where the beaver gnawed through the trunk. Felled trees are typically 2 to 6 inches in diameter, though beavers can fell trees larger than 10 inches. You may see branches stripped of bark, wood chips at the water's edge, and a dam constructed from branches, mud, and stones across a stream. Beaver lodges appear as mound-shaped structures made of sticks and mud rising above the water line. Beaver trails, muddy ramps, and slides leading from water to land are also reliable signs.

American Beavers in Washington typically weigh 30 to 65 pounds at full maturity. Some large males can exceed 60 pounds. Body length ranges from 24 to 35 inches, not including the tail. Kits (young beavers) weigh only 1 pound at birth and reach adult size by two to three years of age. Beavers grow throughout their lives, so the largest individuals are often the oldest. The flat tail, which can measure 10 to 15 inches long and 5 to 6 inches wide, adds significant length and distinctive silhouette to the animal.

Beavers are primarily nocturnal and most active at night, from dusk through the early morning hours. However, they are not strictly confined to darkness and may be active during cloudy days or emerge in the late afternoon, especially during fall and early spring. Beavers are most vocal and visible during their peak activity season of March through May, when sightings in Washington average over 450 observations monthly. If you spot a beaver during the day, it is likely engaged in dam repair, feeding, or lodge construction rather than resting.

American Beavers are herbivorous and prefer the bark, leaves, and twigs of certain tree species. In Washington, they favor aspen, cottonwood, willow, birch, and alder. They also eat aquatic vegetation such as water lilies, cattails, and sedges when available. Beavers do not eat the wood itself but rather strip the nutritious bark. During fall and early winter, they fell trees and store the branches underwater near their lodge as a food cache for winter months when ice may cover surface vegetation. Each beaver family requires a substantial territory to secure adequate food.

Beavers use vocalizations, scent marking, and body language to communicate within family groups. They produce hisses, grunts, and whines when interacting with each other, particularly between adults and kits. A startled or threatened beaver will slap its flat tail loudly against the water surface, creating a sharp warning sound that carries for long distances and alerts other beavers to danger. This tail slap is one of the most distinctive beaver behaviors you may hear near active beaver waters. Beavers also mark their territory with scent mounds made of mud and castoreum, a pungent secretion from their scent glands.

American Beavers are present statewide in Washington, from the western lowlands of Puget Sound to the Cascades and the Blue Mountains of eastern Washington, provided suitable freshwater habitat exists. They thrive in rivers, streams, ponds, and lakes where vegetation is available. Beavers are absent only in areas lacking permanent water sources or where habitat has been severely degraded. The species is most abundant in the lower elevation watersheds of the Cascade foothills and the valleys of western Washington. iNaturalist records show consistent sightings across all seasons and regions.

Beavers build dams to create impoundments of water that provide safety, stable water depth, and access to food and building materials. A deeper pond protects beavers from predators, keeps lodge entrances submerged and hidden, and allows them to move safely through water. Dams also stabilize water levels against seasonal fluctuations, ensuring that lodge entrances remain underwater during drought or freeze-thaw cycles. The backed-up water inundates nearby trees and vegetation, making them accessible for feeding and dam construction. Beaver dams can significantly alter local hydrology and create wetland habitat used by many other species.

American Beavers typically live 5 to 7 years in the wild, though some individuals have been recorded living up to 10 or more years in protected populations. Mortality in younger beavers is higher due to predation and disease. Once established in a territory, adult beavers are relatively long-lived, and mated pairs may occupy the same location for many years. Beavers face predation from coyotes, mountain lions, bears, and wolves in Washington, and human trapping historically reduced populations significantly. Today, beavers have recovered across much of their historical range in the state.