(Castor canadensis)
Conservation • Description • Habitat • Ecology • Distribution • Taxonomy
Conservation Status |
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| IUCN Red List | LC - Least Concern |
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| NatureServe | N5 - Secure SNR - Unranked |
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| Minnesota | not listed |
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American beaver is the largest rodent in North America. The head and body length is
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.
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
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 |
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Sources Biodiversity occurrence data published by: Minnesota Biodiversity Atlas (accessed through the Minnesota Biodiversity Atlas Portal, bellatlas.umn.edu, 12/25/2025). Timm, R. M. 1975. Distribution, natural history, and parasites of mammals of Cook County, Minnesota. Occasional Papers, Bell Museum of Natural History, University of Minnesota 14:1–56. Hazard, Evan B. 1982. The Mammals of Minnesota. University of Minnesota Press, Minneapolis, Minnesota. 280 pp. The counties in light green lack modern records but have historic county or township specimens or records. |
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| 12/25/2025 | ||
Occurrence |
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Common |
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Class
Subclass
Theria
Infraclass
Placentalia (Placental Mammals)
Magnorder
Boreoeutheria
Superorder
Euarchontoglires (Primates, Rodents, and Allies)
Order
Rodentia (Rodents)
Suborder
Supramyomorpha
Infraorder
Castorimorphi
Superfamily
Castoroidea
Family
Castoridae (Beavers)
Subfamily
Castorinae
Genus
Castor (Beavers)
Suborder
The classification of the American Beaver above the family level is currently subject to revision based on modern phylogenetic research. The traditional classification places the family Castoridae (Beavers) in the suborder Castorimorpha.
Molecular DNA studies have established three monophyletic rodent clades, recognized as the suborders Hystricomorpha, Sciuromorpha, and Supramyomorpha, a new suborder that includes the family Castoridae.
The suborder Castorimorpha is currently the designation found in many online resources, including the Catalogue of Life. The suborder Supramyomorpha is the designation used by the Mammal Diversity Database (MDD) of the American Society of Mammalogists (ASM).
MinnesotaSeasons.com follows the classification adopted by the Mammal Diversity Database (MDD), as it represents the most current, scientifically vetted taxonomy (see Burgin et al., 2025).
Historically, up to 25 subspecies of the American Beaver (Castor canadensis) were described, often based on minor differences in size, pelage color, and skull morphology across their wide North American range.
However, recent comprehensive genetic studies have generally not supported these traditional subspecies classifications. Consequently, major modern taxonomic authorities, including the Integrated Taxonomic Information System (ITIS) and the Mammal Diversity Database (MDD), currently do not recognize any subspecies for Castor canadensis, treating it as a single, widespread species across its native range.
Castor caecator
Castor canadensis ssp. acadicus
Castor canadensis ssp. phaeus
Castor canadensis ssp. idoneus
Castor canadensis ssp. rostralis
Castor canadensis ssp. sagittatus
Castor canadensis ssp. baileyi
Castor canadensis ssp. carolinensis
Castor canadensis ssp. concisor
Castor canadensis ssp. repentinus
Castor canadensis ssp. belugae
Castor canadensis ssp. duchesnei
Castor canadensis ssp. subauratus
Castor canadensis ssp. labradorensis
Castor canadensis ssp. missouriensis
Castor canadensis ssp. caecator
Castor canadensis ssp. canadensis
Castor canadensis ssp. leucodontus
Castor canadensis ssp. pallidus
Castor canadensis ssp. mexicanus
Castor canadensis ssp. shastensis
Castor canadensis ssp. frondator
Castor canadensis ssp. taylori
Castor canadensis ssp. texensis
Castor canadensis ssp. pacificus
Castor canadensis ssp. michiganensis
Castor subauratus ssp. shastensis
Castor subauratus ssp. subauratus
American beaver
Canadian beaver
North American beaver
Glossary
Cambium
A layer of softer growing tissue, one to several cells thick, under the bark of trees.
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Ramona Abrego |
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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. |
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Lynn Rubey |
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American beaver near the opening of the den in the bank along the river in The Big Stone National Wildlife Refuge. |
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Beaver dam |
Beaver-gnawed tree |
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Beaver |
Dam |
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Dam |
Dam |
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Lodge |
Lodge |
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Sign |
Sign |

Beaver
DianesDigitals
Beaver
Craig A. Mullenbach

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"A Quick Look at a Beaver Feeding etc."
Published on Jul 12, 2016
North American Beaver - Tail Slap @ Iron Mtn.
JCVdude
North American Beaver.mov
RDWildlife

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Be sure to include a location.
Jake
5/17/2020
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
9/3/2019
Ramona Abrego
5/17/2019
