American Beaver

Castor canadensis

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Photo of a beaver on land, chewing on a log
A beaver’s lips close behind its front teeth, allowing it to chomp trees with its mouth closed.
Glenn Chambers
Family

Castoridae (beavers) in the order Rodentia

Description

The American beaver is a large rodent associated with waterways and wetlands. It has webbed hind feet; a large, relatively hairless, horizontally flattened tail; a blunt head with small eyes and ears; a short neck; and a stout body. The color is a uniform dark brown above with lighter underparts and a blackish tail.

Similar species: Two other aquatic rodents in Missouri might be confused with beavers. The common muskrat, found statewide, has a long tail that is slightly flattened vertically, and it is a smaller animal, usually only weighing 2–4 pounds. The introduced nutria, which sometimes occurs in southeastern Missouri, has a tail that is round in cross-section, and at 15–25 pounds, it is intermediate in size between beaver and muskrat.

Size

Total length: 34–54 inches; tail length: 9–17 inches; weight: 26–90 pounds.

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Photo of a beaver crouched on land
Beaver
A beaver has webbed hind feet; a large, relatively hairless, horizontally flattened tail, a blunt head, small eyes and ears, a short neck, and a stout body.

Beaver_3-2-17.jpg

Photo of a beaver half in water
Beaver
In spring and fall, beavers eat woody and nonwoody vegetation. In summer, mostly nonwoody plants are eaten; in winter, mostly woody foods are eaten.

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Photo of a beaver swimming
Beaver
Despite an extreme reduction in their colonies by about 1900, Missouri’s beaver population has been reestablished throughout the state.

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Beaver cut tree
Beaver Cut Tree
A tree that has been cut down by a beaver.

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Photo of a beaver dam
Beaver Dam
Though beavers are famous for dam building, in Missouri they are less likely to construct dams than they are in regions farther west and north.

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Photo of a beaver lodge in a wetlands area, with cattails in the background
Beaver Lodge at Cosmo Park, Columbia, Missouri
In Missouri, beaver usually do not construct lodges and dams. The beaver lodge at Columbia's Cosmo Park was a notable exception.

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Photo of a young beaver crouched on a muddy bank
Young Beaver
Young beavers are weaned after about 6 weeks but remain with the family for about 2 years.

FG-0023_Beaver.mp4

Video of a beaver in the wild

Beaver

Audio clip of beaver sounds
Habitat and conservation

In Missouri, beavers live in and along streams, rivers, marshes, and small lakes. Though they are famous for dam building, in Missouri they are less likely to construct dams than they are in regions farther west and north. Instead, in our faster and fluctuating streams, they usually excavate a den in a high bank. In both lodges and bankside dens, the entrance is usually below water. Beaver restoration efforts have brought their numbers to levels allowing an annual harvest.

Foods

In spring and fall, beavers eat woody and nonwoody vegetation. In summer, they eat mostly nonwoody plants; in winter, they eat mostly woody plants. Woody foods include the bark, new twigs, and new bark growth of a variety of trees and woody vines ranging from willows and cottonwood to oaks, hickories, sycamores, and wild grapevines. Nonwoody foods include corn, pond lilies, watercress, and many other herbaceous plants.

image of Beaver Distribution Map
Distribution in Missouri

Beavers occur statewide near streams and wetlands. They are least common in the Mississippi Lowlands.

Status

Despite an extreme reduction in their colonies by about 1900, Missouri’s beaver population has been reestablished statewide.

Life cycle

Beavers are usually nocturnal but may also come out in the daytime, especially in fall when they are busy gathering food and preparing their dams and lodges for winter. They live in colonies — family groups comprising an adult male and female and their yearlings and kits. Breeding begins in January and February, and a single litter of usually 3 or 4 young is born in April, May, or June. The young are weaned after about 6 weeks but remain with the family for about 2 years.

Human connections

Beavers are harvested for their fur, which is used in coats and trimmings. Some people enjoy eating beaver meat. In the past, beaver fur, meat, and oil were immensely important in attracting both Native Americans and European settlers to our region.

Ecosystem connections

Across the continent, the historic value of beaver damming is hard to estimate, when you consider their long-term impact on stream flow, creation of ponds, and causing silt to settle and create fertile valleys. This development of new habitats has a profound effect on the many other plants and animals requiring such conditions.

Signs & Tracks

Front track:

  • 3½ inches long
  • 5 toes, though often only 3 or 4 toes leave a track.

Hind track:

  • 6–7 inches long, 5 inches wide
  • 5 toes, though often only 3 or 4 toes leave a track
  • toes are webbed, though the marks are not always distinct
  • hind track is often confused with goose tracks.

Other notes:

  • Beaver are common on banks of rivers and other aquatic habitats where trees are nearby.
  • On steep banks, look for scratch marks.
  • Hind tracks are positioned just in front of the front tracks, but often they land directly on top of the front tracks so that the front tracks are indistinguishable.
  • The flat tail often drags down the middle, sometimes obliterating foot tracks.
  • The claws leave marks.
  • Toe pad prints and heel pad prints are not separated (the entire finger leaves print).
  • Look for other beaver sign, especially their distinctively gnawed and felled trees and branches.
  • Trees are usually cut in autumn. In the summer, beaver eat more green foods, such as giant ragweed.
  • Beaver generally forge a trail and then stick to it. Thus their tracks often overlap a great deal. Over time, the trail can turn into a little trench.
  • Scats are not commonly seen, because beaver usually poop in the water. Scats are sometimes seen in ice in winter.