American beaver

(Castor canadensis)

Conservation Status
American beaver
  IUCN Red List

LC - Least Concern


N5 - Secure

SNR - Unranked


not listed


American beaver is the largest rodent in North America. The head and body length is 25 to 30. A mature adult usually weighs 44 to 59 pounds, though they can be much larger.

The body is stout. The powerful hind legs are longer than the front legs so the rear end is higher than the front end when the beaver walks. The coat is reddish-brown or blackish-brown, glossy, and thick. The hind legs and have webbed feet. The claw on the second toe is doubled and functions as a comb.

The skull is disproportionately large. There are 20 teeth, including disproportionately large upper and lower incisors. The incisors are ¾ to 1 long and about ¼ wide, and have chestnut brown enamel. The ears and nostrils are closable.

The tail is broad and flat—paddle shaped. It is 9 to 10 long, naked, and scaly.




Head and body: 25 to 30

Tail: 9 to 10




Dams – A beaver will build a dam in a stream or river to slow the flow of water. Where sufficient stable water is available it will not build a dam but rather burrow into the bank. The front (downstream) side of a dam consists of large branches with the but ends facing downstream. Mud and debris make up the center of the dam. The back (upstream) side is made up of small branches.

Lodges – A lodge is a large pile of branches covered with mud, debris, and aquatic vegetation. It can rise up to 10 feet above the pond floor. It is excavated from within. In the winter, vapor can often be seen rising from a thinly covered opening used for ventilation (smoke hole) at the top of the lodge. Lodges are usually built near or at the edges of lakes and ponds.

Canals – A canal may be up to two feet wide and deep. It provides a safe water passage and can be used to help transport felled trees to the pond.

Cut trees – After downing a tree or branch a beaver may completely strip the outer bark to get at the cambium. Tree stumps near pond edges may show ¼ wide incisor marks.

Scat – Beavers defecate in the water.


Similar Species

  The stout build, brown fur, and flat, broad, scaly tail make identification unmistakable.  

Lodges built on islands, banks of ponds,and shores of lakes








10 to 12 years


Life Cycle


Beavers are mostly nocturnal, though they are occasionally seen during the day. They are usually found in colonies of 4 to 10 related individuals.

Females usually breed first in their second year, sometimes in their third year. Gestation is 100 to 128 days. Between April and June the give birth to usually four or more kits, averaging five in Minnesota. The young remain with the parents until their second year, when they are either driven out or choose to leave. They usually relocate within six miles. The average life span is 11 years.




Bark, cambium, and small twigs of aspen, poplar, birch, maple, willow, beech, and alder. Aquatic vegetation.


Distribution Map



7, 15, 24, 29, 30, 76.

Missouri River beaver (Castor canadensis missouriensis) is found in the southwest.

Northeastern beaver (Castor canadensis canadensis) is found in the remainder of the state

Woods beaver (Castor canadensis michiganensis) may be found in the northeast.





  Class Mammalia (mammals)  
  Subclass Theria  
  Infraclass Placentalia (placental mammals)  
  Superorder Euarchontoglires (primates, rodents, and allies)  
  Order Rodentiia (rodents)  
  Suborder Castorimorpha (beavers, pocket gophers, and allies)  


Castoridae (beavers)  


Castor (beavers)  

Subordinate Taxa


Acadian beaver (Castor canadensis acadicus)

Admiralty beaver (Castor canadensis phaeus)

American beaver (Castor canadensis idoneus)

American beaver (Castor canadensis rostralis)

American beaver (Castor canadensis sagittatus)

Bailey’s beaver (Castor canadensis baileyi)

Carolina beaver (Castor canadensis carolinensis)

Colorado beaver (Castor canadensis concisor)

Colorado River beaver (Castor canadensis repentinus)

Cook Inlet beaver (Castor canadensis belugae)

Duchesne River beaver (Castor canadensis duchesnei)

golden beaver (Castor canadensis subauratus)

Labrador beaver (Castor canadensis labradorensis)

Missouri River beaver (Castor canadensis missouriensis)

Newfoundland beaver (Castor canadensis caecator)

northeastern beaver (Castor canadensis canadensis)

Pacific beaver (Castor canadensis leucodontus)

pallid beaver (Castor canadensis pallidus)

Rio Grande beaver (Castor canadensis mexicanus)

Shasta Mt beaver (Castor canadensis shastensis)

Sonora beaver (Castor canadensis frondator)

Taylor’s beaver (Castor canadensis taylori)

Texas beaver (Castor canadensis texensis)

Washington beaver (Castor canadensis pacificus)

woods beaver (Castor canadensis michiganensis) (?)




Castor caecator


Common Names


American beaver

Canadian beaver

North American beaver










A layer of softer growing tissue, one to several cells thick, under the bark of trees.

Visitor Photos

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Ramona Abrego


Beaver working on his house collecting material and packing over the branches and even came up to the shore within 5 feet of me to get a good look at me and raised his body up out of the water.

  American beaver  
    American beaver   American beaver  
    American beaver      

Lynn Rubey


American beaver near the opening of the den in the bank along the river in The Big Stone National Wildlife Refuge.

  American beaver  

Kirk Nelson


Beaver dam

    American beaver      

Beaver-gnawed tree

    American beaver      


    American beaver      


    American beaver   American beaver  
    American beaver      


    American beaver   American beaver  


    American beaver   American beaver  




Copyright DianesDigitals

Craig A. Mullenbach



Visitor Videos

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Dan W. Andree

  "A Quick Look at a Beaver Feeding etc."
Published on Jul 12, 2016

This short video shows some interesting eating behavior of a beaver as well as a little tail slapping. Filmed early spring 2016.

Other Videos
  North American Beaver - Tail Slap @ Iron Mtn.

Uploaded on Sep 23, 2010

The beaver (genus Castor) is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver (Castor canadensis) (native to North America) and European Beaver (Castor fiber) (Eurasia). Beavers are known for building dams, canals, and lodges (homes). They are the second-largest rodent in the world (after the capybara). Their colonies create one or more dams to provide still, deep water to protect against predators, and to float food and building material. The North American beaver population was once more than 60 million, but as of 1988 was 6--12 million. This population decline is due to extensive hunting for fur, for glands used as medicine and perfume, and because their harvesting of trees and flooding of waterways may interfere with other land uses.

Beavers are known for their natural trait of building dams on rivers and streams, and building their homes (known as "lodges") in the resulting pond. Beavers also build canals to float build materials that are difficult to haul over land. They use powerful front teeth to cut trees and other plants that they use both for building and for food. In the absence of existing ponds, beavers must construct dams before building their lodges. First they place vertical poles, then fill between the poles with a crisscross of horizontally placed branches. They fill in the gaps between the branches with a combination of weeds and mud until the dam impounds sufficient water to surround the lodge.

A beaver skeleton

A beaver skeleton on display at The Museum of Osteology, Oklahoma City, Oklahoma.

They are known for their alarm signal: when startled or frightened, a swimming beaver will rapidly dive while forcefully slapping the water with its broad tail, audible over great distances above and below water. This serves as a warning to beavers in the area. Once a beaver has sounded the alarm, nearby beavers dive and may not reemerge for some time. Beavers are slow on land, but are good swimmers that can stay under water for as long as 15 minutes.

Beavers are herbivores, and prefer the wood of quaking aspen, cottonwood, willow, alder, birch, maple and cherry trees. They also eat sedges, pondweed, and water lilies.

  North American

Uploaded on Oct 3, 2011

During our careers, we have spent a tremendous amount of time in and around beaver (Castor canadensis) habitat. While it has been very common to see beaver at a distance in the water, they generally reserve their land travels for night time. So yesterday, we were surprised and delighted to see this beaver just a few feet away browsing on willow. This stretch of the Rio Grande is currently dry, thereby causing this beaver to adapt to living alongside the highway in a small storm water drainage area. If you watch closely, you'll notice multiple bite marks and damage to the left eye. We believe he likely escaped one of our many native predators (no water, no protection). Our company provides non lethal beaver management solutions, call us today 505.818.7396 or visit to learn more.




Visitor Sightings

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Location: Palmyra Township, Renville County

Many willow observed cut down around man-made pond over the early spring.  Sighted the young beaver early AM. Sighting location is over 10 miles from the Minnesota River and is not near any natural waterways.

  Lynn Rubey

Location: Big Stone National Wildlife Refuge

American beaver near the opening of the den in the bank along the river in The Big Stone National Wildlife Refuge.

American beaver

  Ramona Abrego

Location: Becker County

Beaver working on his house collecting material and packing over the branches and even came up to the shore within 5 feet of me to get a good look at me and raised his body up out of the water.

American beaver

  Kirk Nelson

Location: Crosby Farm Regional Park

Beaver-gnawed tree

American beaver





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