FaunaHub

North American Beaver (Castor canadensis)

MammalRodentWetland

A North American beaver (Castor canadensis) on a grassy bank beside a tree trunk, its thick brown fur glossy in the sun and a front paw raised to its mouth.

A North American beaver on a bank in Algonquin Provincial Park, Ontario, Canada.

Image: Ryan Hodnett, CC BY-SA 4.0, via Wikimedia Commons.

Overview

The North American beaver (Castor canadensis) is a large, stout aquatic rodent, the largest in North America and the second largest in the world after the capybara. Native from Alaska and Canada through most of the United States into northern Mexico, it dams streams into ponds and builds lodges of sticks and mud, and it has been introduced to Tierra del Fuego and parts of Eurasia.

It has a broad, flat, relatively hairless tail covered in blackish scales, webbed hind feet and dexterous front paws, and its dense fur is yellowish or reddish brown to almost black above and paler below. Its large orange incisors grow continuously. The tail, black in the young and lighter with age, serves as a rudder and a prop, and underwater the nostrils and ears seal and a membrane covers the eyes. It differs from the European beaver (Castor fiber) in chromosome number, and the two do not hybridize.

Total length is given as 34–54 inches in one account, and a large beaver may measure 1.3 m including its 30-cm tail; the tail is about 25 cm long by another account, or 8–12 or 9–17 inches. Adults weigh on average 16 to 32 kg by one account; other ranges are 16 to 30 kg and 13 to 32 kg with no age stated, and 18–47 kg for adults. Some may weigh more than 45 kg, and the heaviest on record weighed 110 pounds (50 kg), though a Texas account says beavers rarely reach 27 kg.

Habitat & Range

Beavers live in streams, rivers, ponds, lakes, marshes and other wetlands, commonly in riparian deciduous or mixed forest with aspen, willow, alder or cottonwood. They need stable water and a stream gradient under 15 percent. A dam creates a pond deep enough not to freeze to the bottom, for moving and storing winter food and for reaching the lodge safely underwater; on fast or fluctuating streams beavers often dig dens in the bank instead, and in Missouri they usually do. The entrance to a lodge or bank den is usually below water.

The native range runs from Alaska and Canada through most of the continental United States into northern Mexico, but beavers are absent from the Arctic tundra, most of Florida and the southwestern deserts. Accounts differ on the northern limit — Alaska and Canada south of the Arctic Circle, or north to the mouths of the Mackenzie and Coppermine rivers on the Arctic Ocean — and one says the beaver has been exterminated in some states and in practically all of its former range in northern Mexico. Brought from Canada to Argentina in 1946, it now occurs in both the Argentine and the Chilean parts of Tierra del Fuego, most widespread in mixed evergreen and deciduous forest but also found in steppe and tundra, and it has also been introduced to Finland, northwestern Russia, Poland, Germany and Austria.

Diet

The North American beaver is a herbivore. It eats the bark, cambium, twigs, leaves and buds of trees and shrubs — favoring aspen, poplar, willow, birch, alder and maple — as well as grasses, herbs and water plants such as water lilies, cattails and duckweed. Herbaceous plants are its main food in late spring and summer and appear to be preferred whenever available, while woody food is eaten most from late fall to early spring; water-lily rhizomes may be eaten all year and are important in winter. Woody food is often stored underwater for winter, and microorganisms in the cecum digest cellulose. Half a hectare of aspen will support one beaver for a year.

Behavior

Beavers are mainly nocturnal, also active around dusk and dawn, and are sometimes out by day, especially in fall while gathering food and readying dams and lodges. They are active all year: where ponds freeze over, a beaver may stay in the lodge or under the ice, feeding on its underwater food store, and in the absence of daylight cues its 'days' lengthen to 26 to 29 hours. If food runs short in winter it can live on fat, including fat stored in the tail after eating more in fall.

Beavers live in family colonies of a breeding pair, the year's kits and the previous year's young, sometimes with older, usually non-breeding subadults; only the colony's dominant female breeds. Accounts differ on colony size — averages of 6 or 7 animals and of 5.1, and maximums of up to 8 or, rarely, 12 — and on fidelity: beavers are usually monogamous and are generally believed to pair for life, though one account says males will mate with other females. The female is the central figure and usually chooses the home site, and the young are usually driven away around their second year of life, just before a new litter is born. Families are territorial, scent-marking mud piles at the edges of their territory, and a tail slap on the water warns other beavers of danger.

Human Interaction & Conservation

Unregulated trapping nearly eliminated the beaver from most of its original range, and with habitat loss it was gone from Pennsylvania and most eastern states by about 1900. Closed trapping seasons and reintroductions restored it over most of the continent. It is harvested for its fur, some people eat its meat, and it is a national symbol of Canada.

Beaver dams can flood roads, farmland and timber, block culverts and may block salmon runs, while beaver wetlands can improve water quality and reduce flood impacts. Introduced from Canada to Argentina in 1946 to sustain the fur industry, beavers turn Nothofagus forest into meadows in Tierra del Fuego, and in Finland, where they were released during a program to reintroduce the European beaver, they compete with the native beavers. IUCN's global assessment lists the North American beaver as Least Concern (2016).

Reproduction & Life Cycle

Beavers mate in winter, mainly from January to March, or in late November or December in the south, and usually bear one litter each spring, typically of 3 or 4 kits. Accounts differ widely on gestation — from 12 weeks to 4 months, including 100, about 105, 105–107, about 107 and 128 days — and on litter size, birth weight, weaning and age at maturity.

Kits are born fully furred with their eyes open, weighing about 450 g in two accounts, and can swim soon after birth. They nurse for about six weeks, or 5 to 7 weeks by another account, though weaning is also put at 2 to 3 months, and young beavers mature sexually at ages given from 1.5 years to about 3 years.

Wild beavers are estimated to live 10 to 12 years, or an average of 10 to 20 years by another account, while a third gives a wild maximum of 11 years. In captivity they live up to 15 years, or 15 to 21 years by another account; the longest recorded captive lifespan is given as 23.4 years in one account and 30 years in another.

Sourced facts

Each value below is traced to the specific reference that states it. Open a row's evidence to see the source, where to look in it, and how firmly it supports the value. Sources checked 2026-10-20.

Sourced facts about the North American Beaver, with the reference supporting each
Distinguishing traitsA large, stout aquatic rodent with a broad, flat, relatively hairless tail covered in blackish scales, webbed hind feet and dexterous front paws. Its dense fur is yellowish or reddish brown to almost black above and paler below, and its large orange incisors grow continuously.Largest rodent in North America, second in the world after the capybara; the sexes are colored alike. The tail, black in the young and lighter with age, serves as rudder and prop. Muskrat tails are narrow and vertically flattened, nutria tails round. It differs from the European beaver (C. fiber) in chromosome number; the two do not hybridize. Nostrils and ears seal underwater; a membrane covers the eyes.
Matches source · Smithsonian's National Zoo and Conservation Biology Institute, Missouri Department of Conservation (Field Guide), Animal Diversity Web (University of Michigan Museum of Zoology), Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Pennsylvania Game Commission, Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group), Belgian Biodiversity Platform (Belgian Forum on Invasive Species) — how we know
Smithsonian's National Zoo and Conservation Biology Institute
Where
Smithsonian's National Zoo and Conservation Biology Institute: Physical Description, Size; Missouri Department of Conservation: Description, Description (similar species); Animal Diversity Web: Physical Description; Natural Science Research Laboratory, Museum of Texas Tech University: DESCRIPTION; Hinterland Who's Who: Description; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description, Pathway; Belgian Biodiversity Platform: More on impacts
Checked by FaunaHub
2026-10-20
Limits
Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
Missouri Department of Conservation (Field Guide)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Physical Description, Size; Missouri Department of Conservation: Description, Description (similar species); Animal Diversity Web: Physical Description; Natural Science Research Laboratory, Museum of Texas Tech University: DESCRIPTION; Hinterland Who's Who: Description; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description, Pathway; Belgian Biodiversity Platform: More on impacts
Checked by FaunaHub
2026-10-20
Limits
State field guide without references; Missouri focus; its size and weight ranges do not state age or sex. Its beaver-control link and trapping-season sentence were not used.
Animal Diversity Web (University of Michigan Museum of Zoology)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Physical Description, Size; Missouri Department of Conservation: Description, Description (similar species); Animal Diversity Web: Physical Description; Natural Science Research Laboratory, Museum of Texas Tech University: DESCRIPTION; Hinterland Who's Who: Description; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description, Pathway; Belgian Biodiversity Platform: More on impacts
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Physical Description, Size; Missouri Department of Conservation: Description, Description (similar species); Animal Diversity Web: Physical Description; Natural Science Research Laboratory, Museum of Texas Tech University: DESCRIPTION; Hinterland Who's Who: Description; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description, Pathway; Belgian Biodiversity Platform: More on impacts
Checked by FaunaHub
2026-10-20
Limits
Texas-focused account (copyright 1994, 2004, 2016); its measurement averages and colony size do not state sample or region. Its sentence on removing problem beavers was not used.
Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Physical Description, Size; Missouri Department of Conservation: Description, Description (similar species); Animal Diversity Web: Physical Description; Natural Science Research Laboratory, Museum of Texas Tech University: DESCRIPTION; Hinterland Who's Who: Description; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description, Pathway; Belgian Biodiversity Platform: More on impacts
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
Pennsylvania Game Commission
Where
Smithsonian's National Zoo and Conservation Biology Institute: Physical Description, Size; Missouri Department of Conservation: Description, Description (similar species); Animal Diversity Web: Physical Description; Natural Science Research Laboratory, Museum of Texas Tech University: DESCRIPTION; Hinterland Who's Who: Description; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description, Pathway; Belgian Biodiversity Platform: More on impacts
Checked by FaunaHub
2026-10-20
Limits
State agency species profile (Wildlife Note text) without references; Pennsylvania focus. The page repeats its text in an embedded data block; excerpts are taken from the plain-text copy. Its links to seasons and bag limits were not used.
Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Physical Description, Size; Missouri Department of Conservation: Description, Description (similar species); Animal Diversity Web: Physical Description; Natural Science Research Laboratory, Museum of Texas Tech University: DESCRIPTION; Hinterland Who's Who: Description; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description, Pathway; Belgian Biodiversity Platform: More on impacts
Checked by FaunaHub
2026-10-20
Limits
Species profile published 2009-12-13, compiled from Jenkins and Busher (1979), the NOBANIS fact sheet (Nummi 2006) and Tierra del Fuego studies. Not used: its management section (trapping and control methods) and its swimming speed (up to 8 km an hour).
Belgian Biodiversity Platform (Belgian Forum on Invasive Species)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Physical Description, Size; Missouri Department of Conservation: Description, Description (similar species); Animal Diversity Web: Physical Description; Natural Science Research Laboratory, Museum of Texas Tech University: DESCRIPTION; Hinterland Who's Who: Description; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description, Pathway; Belgian Biodiversity Platform: More on impacts
Checked by FaunaHub
2026-10-20
Limits
Short invasive-species record for Belgium (published 23 March 2009, updated 22 July 2022); Belgian focus; used for one statement only.
Geographic rangeNative to North America, from Alaska and Canada through most of the US into northern Mexico; absent from the Arctic tundra, most of Florida and the southwestern deserts. Introduced to Tierra del Fuego (Argentina and Chile) and Eurasia, including Finland and northwestern Russia.sources disagreeBrought from Canada to Argentina in 1946, it occurs in both countries' parts of Tierra del Fuego, has crossed sea gaps of about 20 km and may have reached the Cape Horn Biosphere Reserve. Eurasian introductions also include Poland, Germany and Austria, and one account adds France. One account says it was exterminated in some US states.
Sources disagree · Mammal Diversity Database (American Society of Mammalogists), Integrated Taxonomic Information System (ITIS), USDA Forest Service, Fire Effects Information System (FEIS), Animal Diversity Web (University of Michigan Museum of Zoology), Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group), PLOS ONE (Huertas Herrera et al. 2020; CADIC-CONICET, Ushuaia, Argentina) — how we know

What each reading says

  • Alaska and Canada south of the Arctic Circle, most of the continental United States (absent from parts of the southwest and most of Florida), extending into northern Mexico — Mammal Diversity Database (American Society of Mammalogists), taxonomic database distribution summary
  • Throughout Canada, north to the mouths of the Mackenzie and Coppermine rivers on the Arctic Ocean; southwestern Alaska and most states south of the 49th parallel; exterminated in practically all of its former range in northern Mexico — Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Canadian government species account
  • Most of North America except the Arctic tundra, peninsular Florida and the Southwestern deserts — USDA Forest Service, Fire Effects Information System (FEIS), U.S. Forest Service literature review
  • All of North America except the northern regions of Canada and the deserts of the southern United States and Mexico — Animal Diversity Web (University of Michigan Museum of Zoology), species account

Accounts give different northern limits: Alaska and Canada south of the Arctic Circle in one; in another, Canada north to the mouths of the Mackenzie and Coppermine rivers on the Arctic Ocean, with only southwestern Alaska included. That account also says it was exterminated in practically all of its former range in northern Mexico, while other accounts include northern Mexico in the range.

Mammal Diversity Database (American Society of Mammalogists)
Where
Mammal Diversity Database: Distribution; Integrated Taxonomic Information System: Geographic Information, Comments; USDA Forest Service, Fire Effects Information System: General Distribution; Animal Diversity Web: Geographic Range; Hinterland Who's Who: Range; Global Invasive Species Database: Summary; PLOS ONE: Abstract, Discussion
Checked by FaunaHub
2026-10-20
Limits
Taxonomic record; distribution is a one-line summary; the page shows no class rank.
Integrated Taxonomic Information System (ITIS)
Where
Mammal Diversity Database: Distribution; Integrated Taxonomic Information System: Geographic Information, Comments; USDA Forest Service, Fire Effects Information System: General Distribution; Animal Diversity Web: Geographic Range; Hinterland Who's Who: Range; Global Invasive Species Database: Summary; PLOS ONE: Abstract, Discussion
Checked by FaunaHub
2026-10-20
Limits
Taxonomic registry; its introduced-range comment repeats the same sentence as MDD; its IUCN status comment is out of date and not used.
USDA Forest Service, Fire Effects Information System (FEIS)
Where
Mammal Diversity Database: Distribution; Integrated Taxonomic Information System: Geographic Information, Comments; USDA Forest Service, Fire Effects Information System: General Distribution; Animal Diversity Web: Geographic Range; Hinterland Who's Who: Range; Global Invasive Species Database: Summary; PLOS ONE: Abstract, Discussion
Checked by FaunaHub
2026-10-20
Limits
Literature review by Tesky (1993), not updated; figures come from older regional studies. Not used: its dated estimate of U.S. nuisance costs ($75 to $100 million a year), its foraging distances and its dispersal distances.
Animal Diversity Web (University of Michigan Museum of Zoology)
Where
Mammal Diversity Database: Distribution; Integrated Taxonomic Information System: Geographic Information, Comments; USDA Forest Service, Fire Effects Information System: General Distribution; Animal Diversity Web: Geographic Range; Hinterland Who's Who: Range; Global Invasive Species Database: Summary; PLOS ONE: Abstract, Discussion
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
Mammal Diversity Database: Distribution; Integrated Taxonomic Information System: Geographic Information, Comments; USDA Forest Service, Fire Effects Information System: General Distribution; Animal Diversity Web: Geographic Range; Hinterland Who's Who: Range; Global Invasive Species Database: Summary; PLOS ONE: Abstract, Discussion
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group)
Where
Mammal Diversity Database: Distribution; Integrated Taxonomic Information System: Geographic Information, Comments; USDA Forest Service, Fire Effects Information System: General Distribution; Animal Diversity Web: Geographic Range; Hinterland Who's Who: Range; Global Invasive Species Database: Summary; PLOS ONE: Abstract, Discussion
Checked by FaunaHub
2026-10-20
Limits
Species profile published 2009-12-13, compiled from Jenkins and Busher (1979), the NOBANIS fact sheet (Nummi 2006) and Tierra del Fuego studies. Not used: its management section (trapping and control methods) and its swimming speed (up to 8 km an hour).
PLOS ONE (Huertas Herrera et al. 2020; CADIC-CONICET, Ushuaia, Argentina)
Where
Mammal Diversity Database: Distribution; Integrated Taxonomic Information System: Geographic Information, Comments; USDA Forest Service, Fire Effects Information System: General Distribution; Animal Diversity Web: Geographic Range; Hinterland Who's Who: Range; Global Invasive Species Database: Summary; PLOS ONE: Abstract, Discussion
Checked by FaunaHub
2026-10-20
Limits
Peer-reviewed remote-sensing study of the invasion in the Tierra del Fuego archipelago (PLoS ONE 15(4): e0232057), read on the publisher's site; dam counts are a proxy for occupancy, from imagery dated 2002 to 2019. Excerpts come only from the Abstract, Results and Discussion: the shared text normaliser drops the span from 'p <0.05' in the abstract to the next '>' character, so the Introduction and Study area cannot be verified. The Introduction says beavers reached the mainland near Punta Arenas, while the Discussion lists the continental mainland among non-invaded areas; neither statement is used.
HabitatStreams, rivers, ponds, lakes, marshes and other wetlands, commonly in riparian deciduous or mixed forest with aspen, willow, alder or cottonwood. It dams streams into ponds and builds lodges of sticks and mud, or digs bank dens; entrances are usually below water.A dam makes a pond deep enough not to freeze to the bottom, for moving and storing winter food and reaching the lodge safely underwater. It needs stable water and a stream gradient under 15 percent. On fast or fluctuating streams it often digs bank dens (usually so in Missouri). In Tierra del Fuego it is most widespread in mixed-evergreen and deciduous forest but also occurs in steppe and tundra.
Matches source · USDA Forest Service, Fire Effects Information System (FEIS), Smithsonian's National Zoo and Conservation Biology Institute, Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Missouri Department of Conservation (Field Guide), Pennsylvania Game Commission, Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Animal Diversity Web (University of Michigan Museum of Zoology), PLOS ONE (Huertas Herrera et al. 2020; CADIC-CONICET, Ushuaia, Argentina) — how we know
USDA Forest Service, Fire Effects Information System (FEIS)
Where
USDA Forest Service, Fire Effects Information System: Plant Communities, Preferred Habitat; Smithsonian's National Zoo and Conservation Biology Institute: Native Habitat; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Habitat and Conservation; Pennsylvania Game Commission: Biology; Hinterland Who's Who: Habitat and Habits; Animal Diversity Web: Habitat; PLOS ONE: Abstract, Results
Checked by FaunaHub
2026-10-20
Limits
Literature review by Tesky (1993), not updated; figures come from older regional studies. Not used: its dated estimate of U.S. nuisance costs ($75 to $100 million a year), its foraging distances and its dispersal distances.
Smithsonian's National Zoo and Conservation Biology Institute
Where
USDA Forest Service, Fire Effects Information System: Plant Communities, Preferred Habitat; Smithsonian's National Zoo and Conservation Biology Institute: Native Habitat; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Habitat and Conservation; Pennsylvania Game Commission: Biology; Hinterland Who's Who: Habitat and Habits; Animal Diversity Web: Habitat; PLOS ONE: Abstract, Results
Checked by FaunaHub
2026-10-20
Limits
Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley)
Where
USDA Forest Service, Fire Effects Information System: Plant Communities, Preferred Habitat; Smithsonian's National Zoo and Conservation Biology Institute: Native Habitat; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Habitat and Conservation; Pennsylvania Game Commission: Biology; Hinterland Who's Who: Habitat and Habits; Animal Diversity Web: Habitat; PLOS ONE: Abstract, Results
Checked by FaunaHub
2026-10-20
Limits
Texas-focused account (copyright 1994, 2004, 2016); its measurement averages and colony size do not state sample or region. Its sentence on removing problem beavers was not used.
Missouri Department of Conservation (Field Guide)
Where
USDA Forest Service, Fire Effects Information System: Plant Communities, Preferred Habitat; Smithsonian's National Zoo and Conservation Biology Institute: Native Habitat; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Habitat and Conservation; Pennsylvania Game Commission: Biology; Hinterland Who's Who: Habitat and Habits; Animal Diversity Web: Habitat; PLOS ONE: Abstract, Results
Checked by FaunaHub
2026-10-20
Limits
State field guide without references; Missouri focus; its size and weight ranges do not state age or sex. Its beaver-control link and trapping-season sentence were not used.
Pennsylvania Game Commission
Where
USDA Forest Service, Fire Effects Information System: Plant Communities, Preferred Habitat; Smithsonian's National Zoo and Conservation Biology Institute: Native Habitat; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Habitat and Conservation; Pennsylvania Game Commission: Biology; Hinterland Who's Who: Habitat and Habits; Animal Diversity Web: Habitat; PLOS ONE: Abstract, Results
Checked by FaunaHub
2026-10-20
Limits
State agency species profile (Wildlife Note text) without references; Pennsylvania focus. The page repeats its text in an embedded data block; excerpts are taken from the plain-text copy. Its links to seasons and bag limits were not used.
Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
USDA Forest Service, Fire Effects Information System: Plant Communities, Preferred Habitat; Smithsonian's National Zoo and Conservation Biology Institute: Native Habitat; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Habitat and Conservation; Pennsylvania Game Commission: Biology; Hinterland Who's Who: Habitat and Habits; Animal Diversity Web: Habitat; PLOS ONE: Abstract, Results
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
Animal Diversity Web (University of Michigan Museum of Zoology)
Where
USDA Forest Service, Fire Effects Information System: Plant Communities, Preferred Habitat; Smithsonian's National Zoo and Conservation Biology Institute: Native Habitat; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Habitat and Conservation; Pennsylvania Game Commission: Biology; Hinterland Who's Who: Habitat and Habits; Animal Diversity Web: Habitat; PLOS ONE: Abstract, Results
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
PLOS ONE (Huertas Herrera et al. 2020; CADIC-CONICET, Ushuaia, Argentina)
Where
USDA Forest Service, Fire Effects Information System: Plant Communities, Preferred Habitat; Smithsonian's National Zoo and Conservation Biology Institute: Native Habitat; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Habitat and Conservation; Pennsylvania Game Commission: Biology; Hinterland Who's Who: Habitat and Habits; Animal Diversity Web: Habitat; PLOS ONE: Abstract, Results
Checked by FaunaHub
2026-10-20
Limits
Peer-reviewed remote-sensing study of the invasion in the Tierra del Fuego archipelago (PLoS ONE 15(4): e0232057), read on the publisher's site; dam counts are a proxy for occupancy, from imagery dated 2002 to 2019. Excerpts come only from the Abstract, Results and Discussion: the shared text normaliser drops the span from 'p <0.05' in the abstract to the next '>' character, so the Introduction and Study area cannot be verified. The Introduction says beavers reached the mainland near Punta Arenas, while the Discussion lists the continental mainland among non-invaded areas; neither statement is used.
DietHerbivore: eats bark, cambium, twigs, leaves and buds of trees and shrubs, favoring aspen, poplar, willow, birch, alder and maple among trees, plus grasses, herbs and aquatic plants such as water lilies, cattails and duckweed. Woody food is often stored underwater for winter.Herbaceous plants are the main food in late spring and summer and appear to be preferred over woody food when available; woody food is eaten most from late fall to early spring. Water-lily rhizomes may be eaten all year and are important in winter. Corn is also eaten. Microorganisms in the cecum digest cellulose. Half a hectare of aspen will support one beaver for a year.
Matches source · USDA Forest Service, Fire Effects Information System (FEIS), Animal Diversity Web (University of Michigan Museum of Zoology), Smithsonian's National Zoo and Conservation Biology Institute, Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Pennsylvania Game Commission, Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Missouri Department of Conservation (Field Guide), Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group) — how we know
USDA Forest Service, Fire Effects Information System (FEIS)
Where
USDA Forest Service, Fire Effects Information System: Food Habits; Animal Diversity Web: Food Habits, Behavior; Smithsonian's National Zoo and Conservation Biology Institute: Food/Eating Habits; Hinterland Who's Who: Feeding; Pennsylvania Game Commission: Biology; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Food; Global Invasive Species Database: Nutrition
Checked by FaunaHub
2026-10-20
Limits
Literature review by Tesky (1993), not updated; figures come from older regional studies. Not used: its dated estimate of U.S. nuisance costs ($75 to $100 million a year), its foraging distances and its dispersal distances.
Animal Diversity Web (University of Michigan Museum of Zoology)
Where
USDA Forest Service, Fire Effects Information System: Food Habits; Animal Diversity Web: Food Habits, Behavior; Smithsonian's National Zoo and Conservation Biology Institute: Food/Eating Habits; Hinterland Who's Who: Feeding; Pennsylvania Game Commission: Biology; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Food; Global Invasive Species Database: Nutrition
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
Smithsonian's National Zoo and Conservation Biology Institute
Where
USDA Forest Service, Fire Effects Information System: Food Habits; Animal Diversity Web: Food Habits, Behavior; Smithsonian's National Zoo and Conservation Biology Institute: Food/Eating Habits; Hinterland Who's Who: Feeding; Pennsylvania Game Commission: Biology; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Food; Global Invasive Species Database: Nutrition
Checked by FaunaHub
2026-10-20
Limits
Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
USDA Forest Service, Fire Effects Information System: Food Habits; Animal Diversity Web: Food Habits, Behavior; Smithsonian's National Zoo and Conservation Biology Institute: Food/Eating Habits; Hinterland Who's Who: Feeding; Pennsylvania Game Commission: Biology; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Food; Global Invasive Species Database: Nutrition
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
Pennsylvania Game Commission
Where
USDA Forest Service, Fire Effects Information System: Food Habits; Animal Diversity Web: Food Habits, Behavior; Smithsonian's National Zoo and Conservation Biology Institute: Food/Eating Habits; Hinterland Who's Who: Feeding; Pennsylvania Game Commission: Biology; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Food; Global Invasive Species Database: Nutrition
Checked by FaunaHub
2026-10-20
Limits
State agency species profile (Wildlife Note text) without references; Pennsylvania focus. The page repeats its text in an embedded data block; excerpts are taken from the plain-text copy. Its links to seasons and bag limits were not used.
Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley)
Where
USDA Forest Service, Fire Effects Information System: Food Habits; Animal Diversity Web: Food Habits, Behavior; Smithsonian's National Zoo and Conservation Biology Institute: Food/Eating Habits; Hinterland Who's Who: Feeding; Pennsylvania Game Commission: Biology; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Food; Global Invasive Species Database: Nutrition
Checked by FaunaHub
2026-10-20
Limits
Texas-focused account (copyright 1994, 2004, 2016); its measurement averages and colony size do not state sample or region. Its sentence on removing problem beavers was not used.
Missouri Department of Conservation (Field Guide)
Where
USDA Forest Service, Fire Effects Information System: Food Habits; Animal Diversity Web: Food Habits, Behavior; Smithsonian's National Zoo and Conservation Biology Institute: Food/Eating Habits; Hinterland Who's Who: Feeding; Pennsylvania Game Commission: Biology; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Food; Global Invasive Species Database: Nutrition
Checked by FaunaHub
2026-10-20
Limits
State field guide without references; Missouri focus; its size and weight ranges do not state age or sex. Its beaver-control link and trapping-season sentence were not used.
Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group)
Where
USDA Forest Service, Fire Effects Information System: Food Habits; Animal Diversity Web: Food Habits, Behavior; Smithsonian's National Zoo and Conservation Biology Institute: Food/Eating Habits; Hinterland Who's Who: Feeding; Pennsylvania Game Commission: Biology; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Missouri Department of Conservation: Food; Global Invasive Species Database: Nutrition
Checked by FaunaHub
2026-10-20
Limits
Species profile published 2009-12-13, compiled from Jenkins and Busher (1979), the NOBANIS fact sheet (Nummi 2006) and Tierra del Fuego studies. Not used: its management section (trapping and control methods) and its swimming speed (up to 8 km an hour).
Body sizeTotal length 34–54 inches; a large beaver may measure 1.3 m including its 30-cm tail. Tail broad and flat, about 25 cm long, also given as 8–12 or 9–17 inches. Stands 1 to 1.5 feet (0.3 to 0.5 m) tall.sources disagreeOther lengths are given without naming the measure: 900–1170 mm, 3 to 4 feet (1 to 1.2 m), up to 1200 mm and up to 40 inches. A Texas account gives averages of 1,160 mm total length and 400 mm tail. The tail of a large beaver may be up to 18 cm wide and 4 cm thick; another account gives 5 to 6 inches wide.
Sources disagree · Missouri Department of Conservation (Field Guide), Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Animal Diversity Web (University of Michigan Museum of Zoology), Smithsonian's National Zoo and Conservation Biology Institute, Pennsylvania Game Commission, Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group) — how we know

What each reading says

  • Total length 34-54 inches; tail 9-17 inches — Missouri Department of Conservation (Field Guide), state field guide; age not stated
  • A large beaver up to 1.3 m including its 30-cm tail; tail up to 18 cm wide and 4 cm thick — Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), large adult
  • Adults up to 40 inches long; tail 8 to 12 inches long and 5 to 6 inches wide — Pennsylvania Game Commission, adults; measure not named
  • Adults up to 1200 mm long — Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group), adults; measure not named

Maximum lengths differ: up to 1.3 m for a large beaver including its tail in one account, and up to 1200 mm or up to 40 inches in two others that do not name the measure, while a field guide gives a total-length range of 34-54 inches; tail-length ranges are 8 to 12 inches in one account and 9-17 inches in another.

Missouri Department of Conservation (Field Guide)
Where
Missouri Department of Conservation: Size; Hinterland Who's Who: Description; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Animal Diversity Web: Physical Description (data panel), Communication and Perception; Smithsonian's National Zoo and Conservation Biology Institute: Size; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description
Checked by FaunaHub
2026-10-20
Limits
State field guide without references; Missouri focus; its size and weight ranges do not state age or sex. Its beaver-control link and trapping-season sentence were not used.
Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
Missouri Department of Conservation: Size; Hinterland Who's Who: Description; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Animal Diversity Web: Physical Description (data panel), Communication and Perception; Smithsonian's National Zoo and Conservation Biology Institute: Size; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley)
Where
Missouri Department of Conservation: Size; Hinterland Who's Who: Description; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Animal Diversity Web: Physical Description (data panel), Communication and Perception; Smithsonian's National Zoo and Conservation Biology Institute: Size; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description
Checked by FaunaHub
2026-10-20
Limits
Texas-focused account (copyright 1994, 2004, 2016); its measurement averages and colony size do not state sample or region. Its sentence on removing problem beavers was not used.
Animal Diversity Web (University of Michigan Museum of Zoology)
Where
Missouri Department of Conservation: Size; Hinterland Who's Who: Description; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Animal Diversity Web: Physical Description (data panel), Communication and Perception; Smithsonian's National Zoo and Conservation Biology Institute: Size; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
Smithsonian's National Zoo and Conservation Biology Institute
Where
Missouri Department of Conservation: Size; Hinterland Who's Who: Description; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Animal Diversity Web: Physical Description (data panel), Communication and Perception; Smithsonian's National Zoo and Conservation Biology Institute: Size; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description
Checked by FaunaHub
2026-10-20
Limits
Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
Pennsylvania Game Commission
Where
Missouri Department of Conservation: Size; Hinterland Who's Who: Description; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Animal Diversity Web: Physical Description (data panel), Communication and Perception; Smithsonian's National Zoo and Conservation Biology Institute: Size; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description
Checked by FaunaHub
2026-10-20
Limits
State agency species profile (Wildlife Note text) without references; Pennsylvania focus. The page repeats its text in an embedded data block; excerpts are taken from the plain-text copy. Its links to seasons and bag limits were not used.
Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group)
Where
Missouri Department of Conservation: Size; Hinterland Who's Who: Description; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Animal Diversity Web: Physical Description (data panel), Communication and Perception; Smithsonian's National Zoo and Conservation Biology Institute: Size; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Species Description
Checked by FaunaHub
2026-10-20
Limits
Species profile published 2009-12-13, compiled from Jenkins and Busher (1979), the NOBANIS fact sheet (Nummi 2006) and Tierra del Fuego studies. Not used: its management section (trapping and control methods) and its swimming speed (up to 8 km an hour).
Body massAdults average 16 to 32 kg in one account; other ranges are 16 to 30 kg (35 to 65 pounds) and 13 to 32 kg with no age stated, and 18–47 kg for adults. Some may weigh more than 45 kg; the heaviest on record weighed 110 pounds (50 kg).sources disagreeAverages are given as 18 kg in a Texas account (rarely as much as 27 kg), 20,250 g for adults in a longevity database and 40 to 60 pounds for adults in Pennsylvania's account, where beavers over 70 pounds have been recorded. A Missouri field guide gives 26-90 pounds, with no age stated.
Sources disagree · Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Smithsonian's National Zoo and Conservation Biology Institute, Animal Diversity Web (University of Michigan Museum of Zoology), Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group), Missouri Department of Conservation (Field Guide), Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Pennsylvania Game Commission, AnAge: The Animal Ageing and Longevity Database (Human Ageing Genomic Resources) — how we know

What each reading says

  • Adults on average 16 to 32 kg; some may weigh more than 45 kg — Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), adults
  • 35 to 65 pounds (16 to 30 kilograms); heaviest on record 110 pounds (50 kilograms) — Smithsonian's National Zoo and Conservation Biology Institute, zoo species account; age not stated
  • 13 to 32 kg — Animal Diversity Web (University of Michigan Museum of Zoology), data panel range; age not stated
  • Adults 18-47 kg — Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group), adults
  • 26-90 pounds — Missouri Department of Conservation (Field Guide), Missouri field guide; age not stated
  • Average 18 kg; rarely as much as 27 kg — Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Texas account
  • Adults average 40 to 60 pounds; over 70 pounds recorded in Pennsylvania — Pennsylvania Game Commission, adults
  • Adult weight 20,250 g — AnAge: The Animal Ageing and Longevity Database (Human Ageing Genomic Resources), life-history database average

Averages differ: 16 to 32 kg and 40 to 60 pounds for adults, 18 kg in a Texas account and 20,250 g for adults in a longevity database. Ranges differ too: 16 to 30 kg, 13 to 32 kg and 26-90 pounds with no age stated, and 18-47 kg for adults. One account says beavers rarely reach 27 kg, while others say some may weigh more than 45 kg and give a record of 50 kg.

Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
Hinterland Who's Who: Description; Smithsonian's National Zoo and Conservation Biology Institute: Size; Animal Diversity Web: Physical Description (data panel); Global Invasive Species Database: Species Description; Missouri Department of Conservation: Size; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Pennsylvania Game Commission: Biology; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
Smithsonian's National Zoo and Conservation Biology Institute
Where
Hinterland Who's Who: Description; Smithsonian's National Zoo and Conservation Biology Institute: Size; Animal Diversity Web: Physical Description (data panel); Global Invasive Species Database: Species Description; Missouri Department of Conservation: Size; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Pennsylvania Game Commission: Biology; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
Animal Diversity Web (University of Michigan Museum of Zoology)
Where
Hinterland Who's Who: Description; Smithsonian's National Zoo and Conservation Biology Institute: Size; Animal Diversity Web: Physical Description (data panel); Global Invasive Species Database: Species Description; Missouri Department of Conservation: Size; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Pennsylvania Game Commission: Biology; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group)
Where
Hinterland Who's Who: Description; Smithsonian's National Zoo and Conservation Biology Institute: Size; Animal Diversity Web: Physical Description (data panel); Global Invasive Species Database: Species Description; Missouri Department of Conservation: Size; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Pennsylvania Game Commission: Biology; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Species profile published 2009-12-13, compiled from Jenkins and Busher (1979), the NOBANIS fact sheet (Nummi 2006) and Tierra del Fuego studies. Not used: its management section (trapping and control methods) and its swimming speed (up to 8 km an hour).
Missouri Department of Conservation (Field Guide)
Where
Hinterland Who's Who: Description; Smithsonian's National Zoo and Conservation Biology Institute: Size; Animal Diversity Web: Physical Description (data panel); Global Invasive Species Database: Species Description; Missouri Department of Conservation: Size; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Pennsylvania Game Commission: Biology; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
State field guide without references; Missouri focus; its size and weight ranges do not state age or sex. Its beaver-control link and trapping-season sentence were not used.
Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley)
Where
Hinterland Who's Who: Description; Smithsonian's National Zoo and Conservation Biology Institute: Size; Animal Diversity Web: Physical Description (data panel); Global Invasive Species Database: Species Description; Missouri Department of Conservation: Size; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Pennsylvania Game Commission: Biology; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Texas-focused account (copyright 1994, 2004, 2016); its measurement averages and colony size do not state sample or region. Its sentence on removing problem beavers was not used.
Pennsylvania Game Commission
Where
Hinterland Who's Who: Description; Smithsonian's National Zoo and Conservation Biology Institute: Size; Animal Diversity Web: Physical Description (data panel); Global Invasive Species Database: Species Description; Missouri Department of Conservation: Size; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Pennsylvania Game Commission: Biology; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
State agency species profile (Wildlife Note text) without references; Pennsylvania focus. The page repeats its text in an embedded data block; excerpts are taken from the plain-text copy. Its links to seasons and bag limits were not used.
AnAge: The Animal Ageing and Longevity Database (Human Ageing Genomic Resources)
Where
Hinterland Who's Who: Description; Smithsonian's National Zoo and Conservation Biology Institute: Size; Animal Diversity Web: Physical Description (data panel); Global Invasive Species Database: Species Description; Missouri Department of Conservation: Size; Natural Science Research Laboratory, Museum of Texas Tech University: Description; Pennsylvania Game Commission: Biology; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Build 15 (03/07/2023). The 23.4-year captive record cites Weigl (2005), rated small sample and acceptable data quality; life-history averages are not tied to wild or captive animals.
LifespanWild: an estimated 10 to 12 years, also given as up to 11 years or an average of 10 to 20 years. Captivity: up to 15 years or 15 to 21 years; the longest recorded captive lifespan is given as 23.4 or 30 years.sources disagreeAccounts that do not say wild or captive give a typical lifespan of 10 to 12 years and a maximum of 12 years. A longevity database rates its 23.4-year captive record as based on a small sample and calls a suggested lifespan of 50 years doubtful.
Sources disagree · Pennsylvania Game Commission, USDA Forest Service, Fire Effects Information System (FEIS), Animal Diversity Web (University of Michigan Museum of Zoology), Smithsonian's National Zoo and Conservation Biology Institute, Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), AnAge: The Animal Ageing and Longevity Database (Human Ageing Genomic Resources) — how we know

What each reading says

  • Wild: estimated 10 to 12 years; captivity: up to 15 years — Pennsylvania Game Commission, state agency account
  • Wild: up to 11 years; captivity: 15 to 21 years — USDA Forest Service, Fire Effects Information System (FEIS), U.S. Forest Service literature review
  • Wild: average 10 to 20 years — Animal Diversity Web (University of Michigan Museum of Zoology), species account
  • Typically 10 to 12 years; oldest on record 30 years in human care — Smithsonian's National Zoo and Conservation Biology Institute, wild or captive not stated for the typical figure
  • May live as long as 12 years — Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), wild or captive not stated
  • Maximum 23.4 years in captivity; a suggested 50 years called doubtful — AnAge: The Animal Ageing and Longevity Database (Human Ageing Genomic Resources), longevity database; small sample

Typical wild lifespan is an estimated 10 to 12 years in one account and an average of 10 to 20 years in another, while a third gives a wild maximum of 11 years, below the upper end of that average range. Captive figures differ: up to 15 years, 15 to 21 years, and recorded maximums of 23.4 and 30 years.

Pennsylvania Game Commission
Where
Pennsylvania Game Commission: Biology; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Lifespan/Longevity; Smithsonian's National Zoo and Conservation Biology Institute: Lifespan; Hinterland Who's Who: Description; AnAge: The Animal Ageing and Longevity Database: Lifespan, ageing, and relevant traits
Checked by FaunaHub
2026-10-20
Limits
State agency species profile (Wildlife Note text) without references; Pennsylvania focus. The page repeats its text in an embedded data block; excerpts are taken from the plain-text copy. Its links to seasons and bag limits were not used.
USDA Forest Service, Fire Effects Information System (FEIS)
Where
Pennsylvania Game Commission: Biology; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Lifespan/Longevity; Smithsonian's National Zoo and Conservation Biology Institute: Lifespan; Hinterland Who's Who: Description; AnAge: The Animal Ageing and Longevity Database: Lifespan, ageing, and relevant traits
Checked by FaunaHub
2026-10-20
Limits
Literature review by Tesky (1993), not updated; figures come from older regional studies. Not used: its dated estimate of U.S. nuisance costs ($75 to $100 million a year), its foraging distances and its dispersal distances.
Animal Diversity Web (University of Michigan Museum of Zoology)
Where
Pennsylvania Game Commission: Biology; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Lifespan/Longevity; Smithsonian's National Zoo and Conservation Biology Institute: Lifespan; Hinterland Who's Who: Description; AnAge: The Animal Ageing and Longevity Database: Lifespan, ageing, and relevant traits
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
Smithsonian's National Zoo and Conservation Biology Institute
Where
Pennsylvania Game Commission: Biology; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Lifespan/Longevity; Smithsonian's National Zoo and Conservation Biology Institute: Lifespan; Hinterland Who's Who: Description; AnAge: The Animal Ageing and Longevity Database: Lifespan, ageing, and relevant traits
Checked by FaunaHub
2026-10-20
Limits
Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
Pennsylvania Game Commission: Biology; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Lifespan/Longevity; Smithsonian's National Zoo and Conservation Biology Institute: Lifespan; Hinterland Who's Who: Description; AnAge: The Animal Ageing and Longevity Database: Lifespan, ageing, and relevant traits
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
AnAge: The Animal Ageing and Longevity Database (Human Ageing Genomic Resources)
Where
Pennsylvania Game Commission: Biology; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Lifespan/Longevity; Smithsonian's National Zoo and Conservation Biology Institute: Lifespan; Hinterland Who's Who: Description; AnAge: The Animal Ageing and Longevity Database: Lifespan, ageing, and relevant traits
Checked by FaunaHub
2026-10-20
Limits
Build 15 (03/07/2023). The 23.4-year captive record cites Weigl (2005), rated small sample and acceptable data quality; life-history averages are not tied to wild or captive animals.
Activity patternMainly nocturnal, also active around dusk and dawn, and sometimes out by day, especially in fall while gathering food and readying dams and lodges. Active all year: where ponds freeze over, it may stay in the lodge or under the ice, feeding on its underwater food store.In the absence of daylight cues its activity is not synchronized with the solar day, and its 'days' lengthen to 26 to 29 hours. If food runs short in winter it can live on fat, including fat stored in the tail after eating more in fall. A Canadian account says that during mild winters and on warm days in March and early April, adults may come out to feed along the shore.
Matches source · Animal Diversity Web (University of Michigan Museum of Zoology), USDA Forest Service, Fire Effects Information System (FEIS), Missouri Department of Conservation (Field Guide), Smithsonian's National Zoo and Conservation Biology Institute, Pennsylvania Game Commission, Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation) — how we know
Animal Diversity Web (University of Michigan Museum of Zoology)
Where
Animal Diversity Web: Behavior, Behavior (Key Behaviors); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Missouri Department of Conservation: Life Cycle; Smithsonian's National Zoo and Conservation Biology Institute: Sleep Habits, Physical Description; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Feeding
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
USDA Forest Service, Fire Effects Information System (FEIS)
Where
Animal Diversity Web: Behavior, Behavior (Key Behaviors); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Missouri Department of Conservation: Life Cycle; Smithsonian's National Zoo and Conservation Biology Institute: Sleep Habits, Physical Description; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Feeding
Checked by FaunaHub
2026-10-20
Limits
Literature review by Tesky (1993), not updated; figures come from older regional studies. Not used: its dated estimate of U.S. nuisance costs ($75 to $100 million a year), its foraging distances and its dispersal distances.
Missouri Department of Conservation (Field Guide)
Where
Animal Diversity Web: Behavior, Behavior (Key Behaviors); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Missouri Department of Conservation: Life Cycle; Smithsonian's National Zoo and Conservation Biology Institute: Sleep Habits, Physical Description; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Feeding
Checked by FaunaHub
2026-10-20
Limits
State field guide without references; Missouri focus; its size and weight ranges do not state age or sex. Its beaver-control link and trapping-season sentence were not used.
Smithsonian's National Zoo and Conservation Biology Institute
Where
Animal Diversity Web: Behavior, Behavior (Key Behaviors); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Missouri Department of Conservation: Life Cycle; Smithsonian's National Zoo and Conservation Biology Institute: Sleep Habits, Physical Description; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Feeding
Checked by FaunaHub
2026-10-20
Limits
Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
Pennsylvania Game Commission
Where
Animal Diversity Web: Behavior, Behavior (Key Behaviors); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Missouri Department of Conservation: Life Cycle; Smithsonian's National Zoo and Conservation Biology Institute: Sleep Habits, Physical Description; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Feeding
Checked by FaunaHub
2026-10-20
Limits
State agency species profile (Wildlife Note text) without references; Pennsylvania focus. The page repeats its text in an embedded data block; excerpts are taken from the plain-text copy. Its links to seasons and bag limits were not used.
Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
Animal Diversity Web: Behavior, Behavior (Key Behaviors); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Missouri Department of Conservation: Life Cycle; Smithsonian's National Zoo and Conservation Biology Institute: Sleep Habits, Physical Description; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Feeding
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
Social structureFamily colonies: a breeding pair, the year's kits and the previous year's young (yearlings), sometimes with older, usually non-breeding subadults. Usually monogamous and generally believed to pair for life. Families are territorial, scent-marking mud piles at territory edges.sources disagreeOnly the colony's dominant female breeds. The female is the central figure and usually chooses the home site; if her mate is lost, another male joins her. Young are usually driven away around their second year of life, just before a new litter is born. A tail slap on the water warns other beavers of danger.
Sources disagree · Smithsonian's National Zoo and Conservation Biology Institute, Missouri Department of Conservation (Field Guide), USDA Forest Service, Fire Effects Information System (FEIS), Animal Diversity Web (University of Michigan Museum of Zoology), Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation) — how we know

What each reading says

  • Family groups of up to 8 related individuals; monogamous, with a new mate sought if one dies — Animal Diversity Web (University of Michigan Museum of Zoology), species account
  • Average colony of 6 or 7 animals, rarely as many as 12; usually monogamous — Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Texas account
  • Average of 5.1 beavers per colony in three age classes; generally monogamous, although males will mate with other females — USDA Forest Service, Fire Effects Information System (FEIS), U.S. Forest Service literature review
  • Takes only one mate, which it keeps for life; if a female's mate is lost, another male joins her — Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Canadian government species account
  • One breeding pair, the year's kits and yearlings, sometimes older subadults; generally believed to pair for life — Smithsonian's National Zoo and Conservation Biology Institute, zoo species account

Colony sizes differ: averages of 6 or 7 animals in a Texas account and 5.1 in another, and maximums of up to 8 related individuals in one account and, rarely, as many as 12 in the Texas account. Accounts also differ on fidelity: one says a beaver keeps one mate for life, while another says pairs are generally monogamous although males will mate with other females.

Smithsonian's National Zoo and Conservation Biology Institute
Where
Smithsonian's National Zoo and Conservation Biology Institute: Social Structure, Reproduction and Development; Missouri Department of Conservation: Life Cycle; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Behavior, Reproduction; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Hinterland Who's Who: Breeding, Description (Signs and sounds)
Checked by FaunaHub
2026-10-20
Limits
Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
Missouri Department of Conservation (Field Guide)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Social Structure, Reproduction and Development; Missouri Department of Conservation: Life Cycle; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Behavior, Reproduction; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Hinterland Who's Who: Breeding, Description (Signs and sounds)
Checked by FaunaHub
2026-10-20
Limits
State field guide without references; Missouri focus; its size and weight ranges do not state age or sex. Its beaver-control link and trapping-season sentence were not used.
USDA Forest Service, Fire Effects Information System (FEIS)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Social Structure, Reproduction and Development; Missouri Department of Conservation: Life Cycle; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Behavior, Reproduction; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Hinterland Who's Who: Breeding, Description (Signs and sounds)
Checked by FaunaHub
2026-10-20
Limits
Literature review by Tesky (1993), not updated; figures come from older regional studies. Not used: its dated estimate of U.S. nuisance costs ($75 to $100 million a year), its foraging distances and its dispersal distances.
Animal Diversity Web (University of Michigan Museum of Zoology)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Social Structure, Reproduction and Development; Missouri Department of Conservation: Life Cycle; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Behavior, Reproduction; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Hinterland Who's Who: Breeding, Description (Signs and sounds)
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Social Structure, Reproduction and Development; Missouri Department of Conservation: Life Cycle; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Behavior, Reproduction; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Hinterland Who's Who: Breeding, Description (Signs and sounds)
Checked by FaunaHub
2026-10-20
Limits
Texas-focused account (copyright 1994, 2004, 2016); its measurement averages and colony size do not state sample or region. Its sentence on removing problem beavers was not used.
Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Social Structure, Reproduction and Development; Missouri Department of Conservation: Life Cycle; USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Animal Diversity Web: Behavior, Reproduction; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Hinterland Who's Who: Breeding, Description (Signs and sounds)
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
ReproductionMates in winter, mainly January to March, and usually bears one litter each spring, typically of 3 or 4 kits. Kits are born fully furred with eyes open and can swim soon after birth. They nurse about six weeks (also given as 5 to 7 weeks); weaning is also put at 2 to 3 months.sources disagreeIn the south, mating may fall in late November or December. Gestation is given as 12 weeks, 100 days, about 105 days, 105–107 days, about 107 days, 128 days or 4 months. Newborns weigh about 450 g, also given as 430 g, about 500 g or about 1 pound. Sexual maturity is given as 1.5 years, about 21 months, 639 days, 2 to 3 years or about 3 years.
Sources disagree · Animal Diversity Web (University of Michigan Museum of Zoology), USDA Forest Service, Fire Effects Information System (FEIS), Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Smithsonian's National Zoo and Conservation Biology Institute, Missouri Department of Conservation (Field Guide), Pennsylvania Game Commission, Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group), AnAge: The Animal Ageing and Longevity Database (Human Ageing Genomic Resources) — how we know

What each reading says

  • Mating January to March in cold climates, late November or December in the south; births usually April to June; gestation about 3 months or 105-107 days (128 days in the data panel); 1 to 4 young, average 3.5; sexually mature at about 3 years — Animal Diversity Web (University of Michigan Museum of Zoology), species account and data panel
  • Breeding January to March; one litter a year from the dominant female; gestation 4 months; average litter 2.3 to 4.1; weaned at 2 to 3 months; swims by 1 week; sexually mature at 2 to 3 years — USDA Forest Service, Fire Effects Information System (FEIS), U.S. Forest Service literature review
  • Mating in January and February; one litter averaging three or four kits, born May or June after a 100-day gestation; newborns about 125 mm long and 450 g, able to swim when born — Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Canadian government species account
  • Breeding January or February; births May or June after about 107 days; one litter of three to four kits a year, with some females having a second in August or September; newborns about 450 g — Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Texas account
  • Breeding January to late February, births in spring; newborns about 1 pound (0.5 kilograms); kits nurse for about six weeks — Smithsonian's National Zoo and Conservation Biology Institute, zoo species account
  • Breeding January and February; usually 3 or 4 young born April, May or June; weaned after about 6 weeks — Missouri Department of Conservation (Field Guide), Missouri field guide
  • 12-week gestation; 3 to 6 (usually 4 or 5) kits born in April or May; newborns about a pound; nursing 5 to 7 weeks; sexually mature at about 21 months — Pennsylvania Game Commission, Pennsylvania account
  • Mating once a year in winter; gestation about 105 days; litter usually three to four, from one to nine; kits about 500 g; sexually mature at 1.5 years, sometimes delayed to 2.5 years or later — Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group), invasive-species profile
  • Gestation 128 days; litter size 3.5; one litter a year; birth weight 430 g; sexual maturity 639 days — AnAge: The Animal Ageing and Longevity Database (Human Ageing Genomic Resources), life-history database averages

Accounts differ on gestation (12 weeks; 100, about 105, 105-107, about 107 or 128 days; about 3 months; 4 months), litter size (averages of 2.3 to 4.1, 3.5, or three or four; ranges of 1 to 4 and one to nine; 3 to 6, usually 4 or 5, in one account), birth weight (about 450 g, 430 g, about 500 g, about 1 pound), nursing or weaning time (about 6 weeks, 5 to 7 weeks, 2 to 3 months) and age at sexual maturity (1.5 years, about 21 months, 639 days, 2 to 3 years, about 3 years).

Animal Diversity Web (University of Michigan Museum of Zoology)
Where
Animal Diversity Web: Reproduction, Reproduction (data panel); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Hinterland Who's Who: Breeding; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Smithsonian's National Zoo and Conservation Biology Institute: Reproduction and Development; Missouri Department of Conservation: Life Cycle; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Reproduction; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
USDA Forest Service, Fire Effects Information System (FEIS)
Where
Animal Diversity Web: Reproduction, Reproduction (data panel); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Hinterland Who's Who: Breeding; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Smithsonian's National Zoo and Conservation Biology Institute: Reproduction and Development; Missouri Department of Conservation: Life Cycle; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Reproduction; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Literature review by Tesky (1993), not updated; figures come from older regional studies. Not used: its dated estimate of U.S. nuisance costs ($75 to $100 million a year), its foraging distances and its dispersal distances.
Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
Animal Diversity Web: Reproduction, Reproduction (data panel); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Hinterland Who's Who: Breeding; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Smithsonian's National Zoo and Conservation Biology Institute: Reproduction and Development; Missouri Department of Conservation: Life Cycle; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Reproduction; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley)
Where
Animal Diversity Web: Reproduction, Reproduction (data panel); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Hinterland Who's Who: Breeding; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Smithsonian's National Zoo and Conservation Biology Institute: Reproduction and Development; Missouri Department of Conservation: Life Cycle; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Reproduction; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Texas-focused account (copyright 1994, 2004, 2016); its measurement averages and colony size do not state sample or region. Its sentence on removing problem beavers was not used.
Smithsonian's National Zoo and Conservation Biology Institute
Where
Animal Diversity Web: Reproduction, Reproduction (data panel); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Hinterland Who's Who: Breeding; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Smithsonian's National Zoo and Conservation Biology Institute: Reproduction and Development; Missouri Department of Conservation: Life Cycle; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Reproduction; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
Missouri Department of Conservation (Field Guide)
Where
Animal Diversity Web: Reproduction, Reproduction (data panel); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Hinterland Who's Who: Breeding; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Smithsonian's National Zoo and Conservation Biology Institute: Reproduction and Development; Missouri Department of Conservation: Life Cycle; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Reproduction; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
State field guide without references; Missouri focus; its size and weight ranges do not state age or sex. Its beaver-control link and trapping-season sentence were not used.
Pennsylvania Game Commission
Where
Animal Diversity Web: Reproduction, Reproduction (data panel); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Hinterland Who's Who: Breeding; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Smithsonian's National Zoo and Conservation Biology Institute: Reproduction and Development; Missouri Department of Conservation: Life Cycle; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Reproduction; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
State agency species profile (Wildlife Note text) without references; Pennsylvania focus. The page repeats its text in an embedded data block; excerpts are taken from the plain-text copy. Its links to seasons and bag limits were not used.
Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group)
Where
Animal Diversity Web: Reproduction, Reproduction (data panel); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Hinterland Who's Who: Breeding; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Smithsonian's National Zoo and Conservation Biology Institute: Reproduction and Development; Missouri Department of Conservation: Life Cycle; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Reproduction; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Species profile published 2009-12-13, compiled from Jenkins and Busher (1979), the NOBANIS fact sheet (Nummi 2006) and Tierra del Fuego studies. Not used: its management section (trapping and control methods) and its swimming speed (up to 8 km an hour).
AnAge: The Animal Ageing and Longevity Database (Human Ageing Genomic Resources)
Where
Animal Diversity Web: Reproduction, Reproduction (data panel); USDA Forest Service, Fire Effects Information System: Timing of Major Life History Events; Hinterland Who's Who: Breeding; Natural Science Research Laboratory, Museum of Texas Tech University: Habits; Smithsonian's National Zoo and Conservation Biology Institute: Reproduction and Development; Missouri Department of Conservation: Life Cycle; Pennsylvania Game Commission: Biology; Global Invasive Species Database: Reproduction; AnAge: The Animal Ageing and Longevity Database: Life history traits (averages)
Checked by FaunaHub
2026-10-20
Limits
Build 15 (03/07/2023). The 23.4-year captive record cites Weigl (2005), rated small sample and acceptable data quality; life-history averages are not tied to wild or captive animals.
Human interactionUnregulated trapping nearly eliminated it from most of its original range; with habitat loss, it was gone from Pennsylvania and most eastern states by about 1900. Closed seasons and reintroductions restored it over most of the continent. It is harvested for its fur, and some people eat its meat.Its dams can flood roads, farmland and timber, block culverts and may block salmon runs; its wetlands can improve water quality and reduce flood impacts. Introduced from Canada to Argentina in 1946 to sustain the fur industry, it turns Nothofagus forest into meadows in Tierra del Fuego. In Finland, released during a reintroduction of the European beaver, it competes with native beavers. It is a national symbol of Canada.
Matches source · Smithsonian's National Zoo and Conservation Biology Institute, Animal Diversity Web (University of Michigan Museum of Zoology), Pennsylvania Game Commission, Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation), Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley), Missouri Department of Conservation (Field Guide), USDA Forest Service, Fire Effects Information System (FEIS), PLOS ONE (Huertas Herrera et al. 2020; CADIC-CONICET, Ushuaia, Argentina), Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group) — how we know
Smithsonian's National Zoo and Conservation Biology Institute
Where
Smithsonian's National Zoo and Conservation Biology Institute: Conservation Efforts; Animal Diversity Web: Conservation Status; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Conservation; Natural Science Research Laboratory, Museum of Texas Tech University: Population Status; Missouri Department of Conservation: Human Connections; USDA Forest Service, Fire Effects Information System: Management Considerations; PLOS ONE: Abstract, Discussion; Global Invasive Species Database: Pathway, Summary, General Impacts
Checked by FaunaHub
2026-10-20
Limits
Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
Animal Diversity Web (University of Michigan Museum of Zoology)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Conservation Efforts; Animal Diversity Web: Conservation Status; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Conservation; Natural Science Research Laboratory, Museum of Texas Tech University: Population Status; Missouri Department of Conservation: Human Connections; USDA Forest Service, Fire Effects Information System: Management Considerations; PLOS ONE: Abstract, Discussion; Global Invasive Species Database: Pathway, Summary, General Impacts
Checked by FaunaHub
2026-10-20
Limits
Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
Pennsylvania Game Commission
Where
Smithsonian's National Zoo and Conservation Biology Institute: Conservation Efforts; Animal Diversity Web: Conservation Status; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Conservation; Natural Science Research Laboratory, Museum of Texas Tech University: Population Status; Missouri Department of Conservation: Human Connections; USDA Forest Service, Fire Effects Information System: Management Considerations; PLOS ONE: Abstract, Discussion; Global Invasive Species Database: Pathway, Summary, General Impacts
Checked by FaunaHub
2026-10-20
Limits
State agency species profile (Wildlife Note text) without references; Pennsylvania focus. The page repeats its text in an embedded data block; excerpts are taken from the plain-text copy. Its links to seasons and bag limits were not used.
Hinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Conservation Efforts; Animal Diversity Web: Conservation Status; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Conservation; Natural Science Research Laboratory, Museum of Texas Tech University: Population Status; Missouri Department of Conservation: Human Connections; USDA Forest Service, Fire Effects Information System: Management Considerations; PLOS ONE: Abstract, Discussion; Global Invasive Species Database: Pathway, Summary, General Impacts
Checked by FaunaHub
2026-10-20
Limits
Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
Natural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Conservation Efforts; Animal Diversity Web: Conservation Status; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Conservation; Natural Science Research Laboratory, Museum of Texas Tech University: Population Status; Missouri Department of Conservation: Human Connections; USDA Forest Service, Fire Effects Information System: Management Considerations; PLOS ONE: Abstract, Discussion; Global Invasive Species Database: Pathway, Summary, General Impacts
Checked by FaunaHub
2026-10-20
Limits
Texas-focused account (copyright 1994, 2004, 2016); its measurement averages and colony size do not state sample or region. Its sentence on removing problem beavers was not used.
Missouri Department of Conservation (Field Guide)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Conservation Efforts; Animal Diversity Web: Conservation Status; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Conservation; Natural Science Research Laboratory, Museum of Texas Tech University: Population Status; Missouri Department of Conservation: Human Connections; USDA Forest Service, Fire Effects Information System: Management Considerations; PLOS ONE: Abstract, Discussion; Global Invasive Species Database: Pathway, Summary, General Impacts
Checked by FaunaHub
2026-10-20
Limits
State field guide without references; Missouri focus; its size and weight ranges do not state age or sex. Its beaver-control link and trapping-season sentence were not used.
USDA Forest Service, Fire Effects Information System (FEIS)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Conservation Efforts; Animal Diversity Web: Conservation Status; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Conservation; Natural Science Research Laboratory, Museum of Texas Tech University: Population Status; Missouri Department of Conservation: Human Connections; USDA Forest Service, Fire Effects Information System: Management Considerations; PLOS ONE: Abstract, Discussion; Global Invasive Species Database: Pathway, Summary, General Impacts
Checked by FaunaHub
2026-10-20
Limits
Literature review by Tesky (1993), not updated; figures come from older regional studies. Not used: its dated estimate of U.S. nuisance costs ($75 to $100 million a year), its foraging distances and its dispersal distances.
PLOS ONE (Huertas Herrera et al. 2020; CADIC-CONICET, Ushuaia, Argentina)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Conservation Efforts; Animal Diversity Web: Conservation Status; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Conservation; Natural Science Research Laboratory, Museum of Texas Tech University: Population Status; Missouri Department of Conservation: Human Connections; USDA Forest Service, Fire Effects Information System: Management Considerations; PLOS ONE: Abstract, Discussion; Global Invasive Species Database: Pathway, Summary, General Impacts
Checked by FaunaHub
2026-10-20
Limits
Peer-reviewed remote-sensing study of the invasion in the Tierra del Fuego archipelago (PLoS ONE 15(4): e0232057), read on the publisher's site; dam counts are a proxy for occupancy, from imagery dated 2002 to 2019. Excerpts come only from the Abstract, Results and Discussion: the shared text normaliser drops the span from 'p <0.05' in the abstract to the next '>' character, so the Introduction and Study area cannot be verified. The Introduction says beavers reached the mainland near Punta Arenas, while the Discussion lists the continental mainland among non-invaded areas; neither statement is used.
Global Invasive Species Database (IUCN SSC Invasive Species Specialist Group)
Where
Smithsonian's National Zoo and Conservation Biology Institute: Conservation Efforts; Animal Diversity Web: Conservation Status; Pennsylvania Game Commission: Species Profile; Hinterland Who's Who: Conservation; Natural Science Research Laboratory, Museum of Texas Tech University: Population Status; Missouri Department of Conservation: Human Connections; USDA Forest Service, Fire Effects Information System: Management Considerations; PLOS ONE: Abstract, Discussion; Global Invasive Species Database: Pathway, Summary, General Impacts
Checked by FaunaHub
2026-10-20
Limits
Species profile published 2009-12-13, compiled from Jenkins and Busher (1979), the NOBANIS fact sheet (Nummi 2006) and Tierra del Fuego studies. Not used: its management section (trapping and control methods) and its swimming speed (up to 8 km an hour).
Conservation statusLeast Concern (LC), global assessment, 2016
Matches source · IUCN Red List of Threatened Species — how we know
IUCN Red List of Threatened Species
Checked by FaunaHub
2026-10-20
Limits
Read from the Red List export IUCN publishes to GBIF; iucnredlist.org itself does not answer automated reads. Categories are reassessed over time.

References for the facts above

  • UniversityAnimal Diversity Web (University of Michigan Museum of Zoology)Supports: range, identification, habitat, diet, body size, body mass, lifespan, activity, social structure, reproduction, human interaction. Retrieved 2026-10-20.Limitations: Student-authored account (Anderson 2002, last updated 2002-10-17) built on older books and web pages. It contradicts itself on gestation (about 3 months or 105-107 days in the text, 128 days from AnAge in its data panel) and on the birth season (April to June in one passage, April to July in another). Its data-panel length range (900 to 1170 mm) does not name the measure. Not used: its weaning statement (within two weeks, up to 90 days) and its IUCN status.
  • UniversityNatural Science Research Laboratory, Museum of Texas Tech University (The Mammals of Texas, 7th ed., Schmidly and Bradley)Supports: identification, habitat, diet, body size, body mass, social structure, reproduction, human interaction. Retrieved 2026-10-20.Limitations: Texas-focused account (copyright 1994, 2004, 2016); its measurement averages and colony size do not state sample or region. Its sentence on removing problem beavers was not used.
  • GovernmentUSDA Forest Service, Fire Effects Information System (FEIS)Supports: range, habitat, diet, lifespan, activity, social structure, reproduction, human interaction. Retrieved 2026-10-20.Limitations: Literature review by Tesky (1993), not updated; figures come from older regional studies. Not used: its dated estimate of U.S. nuisance costs ($75 to $100 million a year), its foraging distances and its dispersal distances.
  • GovernmentHinterland Who's Who (Environment and Climate Change Canada and the Canadian Wildlife Federation)Supports: identification, range, habitat, diet, body size, body mass, lifespan, activity, social structure, reproduction, human interaction. Retrieved 2026-10-20.Limitations: Canadian Wildlife Service text (copyright 1973 to 2017; revised by G. Trottier 1989 and 2003 and G. A. Hood 2017) without in-text references; Canadian focus. Not used: its statements on trapping and flood-control devices as management, its swimming speed and its lodge and canal dimensions.
  • UniversitySmithsonian's National Zoo and Conservation Biology InstituteSupports: identification, habitat, diet, body size, body mass, lifespan, activity, social structure, reproduction, human interaction. Retrieved 2026-10-20.Limitations: Undated zoo species account without in-text references; its size, weight and typical-lifespan figures do not say whether they describe wild or captive animals. Not used: its swimming speed (up to 6 mph) and lodge dimensions, which differ from other accounts.
  • GovernmentMissouri Department of Conservation (Field Guide)Supports: identification, habitat, diet, body size, body mass, activity, social structure, reproduction, human interaction. Retrieved 2026-10-20.Limitations: State field guide without references; Missouri focus; its size and weight ranges do not state age or sex. Its beaver-control link and trapping-season sentence were not used.
  • GovernmentPennsylvania Game CommissionSupports: identification, habitat, diet, body size, body mass, lifespan, activity, reproduction, human interaction. Retrieved 2026-10-20.Limitations: State agency species profile (Wildlife Note text) without references; Pennsylvania focus. The page repeats its text in an embedded data block; excerpts are taken from the plain-text copy. Its links to seasons and bag limits were not used.
  • ReferenceAnAge: The Animal Ageing and Longevity Database (Human Ageing Genomic Resources)Supports: lifespan (maximum recorded longevity in captivity), body mass (average), reproduction (life-history averages). Retrieved 2026-10-20.Limitations: Build 15 (03/07/2023). The 23.4-year captive record cites Weigl (2005), rated small sample and acceptable data quality; life-history averages are not tied to wild or captive animals.
  • ReferenceGlobal Invasive Species Database (IUCN SSC Invasive Species Specialist Group)Supports: range (native and introduced), identification, habitat, diet, body size, body mass, reproduction, human interaction (introduction pathways and impacts). Retrieved 2026-10-20.Limitations: Species profile published 2009-12-13, compiled from Jenkins and Busher (1979), the NOBANIS fact sheet (Nummi 2006) and Tierra del Fuego studies. Not used: its management section (trapping and control methods) and its swimming speed (up to 8 km an hour).
  • ReferencePLOS ONE (Huertas Herrera et al. 2020; CADIC-CONICET, Ushuaia, Argentina)Supports: range (introduced population in Tierra del Fuego), habitat (introduced range), human interaction (introduction and impacts). Retrieved 2026-10-20.Limitations: Peer-reviewed remote-sensing study of the invasion in the Tierra del Fuego archipelago (PLoS ONE 15(4): e0232057), read on the publisher's site; dam counts are a proxy for occupancy, from imagery dated 2002 to 2019. Excerpts come only from the Abstract, Results and Discussion: the shared text normaliser drops the span from 'p <0.05' in the abstract to the next '>' character, so the Introduction and Study area cannot be verified. The Introduction says beavers reached the mainland near Punta Arenas, while the Discussion lists the continental mainland among non-invaded areas; neither statement is used.
  • ReferenceBelgian Biodiversity Platform (Belgian Forum on Invasive Species)Supports: identification (chromosome difference from the Eurasian beaver). Retrieved 2026-10-20.Limitations: Short invasive-species record for Belgium (published 23 March 2009, updated 22 July 2022); Belgian focus; used for one statement only.
  • ReferenceIntegrated Taxonomic Information System (ITIS)Supports: identity cross-check (TSN 180212, valid, 25 synonyms, class Mammalia); range (native jurisdictions, introduced range). Retrieved 2026-10-20.Limitations: Taxonomic registry; its introduced-range comment repeats the same sentence as MDD; its IUCN status comment is out of date and not used.
  • ReferenceMammal Diversity Database (American Society of Mammalogists)Supports: identity: accepted name, authorship, classification, synonyms; range (distribution summary and introduced range). Retrieved 2026-10-20.Limitations: Taxonomic record; distribution is a one-line summary; the page shows no class rank.
  • ReferenceIUCN Red List of Threatened SpeciesSupports: The global Red List category and the year of the assessment. Retrieved 2026-10-20.Limitations: Read from the Red List export IUCN publishes to GBIF; iucnredlist.org itself does not answer automated reads. Categories are reassessed over time.

Frequently Asked Questions — North American Beaver

Why do beavers build dams?
A dam creates a pond deep enough not to freeze to the bottom, so that beavers can move and store their winter food by swimming and reach the lodge safely underwater all year.
What do beavers eat?
They are herbivores: bark, twigs, leaves and buds of trees such as aspen, poplar, willow and birch, plus grasses, herbs and water plants. Herbaceous plants are the main food in late spring and summer, and woody food from late fall to early spring.
How big is a North American beaver?
It is the largest rodent in North America. Adults weigh on average 16 to 32 kg by one account, and some may weigh more than 45 kg, though another account says beavers rarely reach 27 kg. A large beaver may measure 1.3 m long including its tail.
Where has the North American beaver been introduced?
It was brought from Canada to Argentina in 1946 and now occurs in both the Argentine and the Chilean parts of Tierra del Fuego. It has also been introduced to parts of Eurasia, including Finland, northwestern Russia, Poland, Germany and Austria.

Sources and further reading

Authoritative wildlife references used for general educational context. Conservation status should always be verified against current IUCN Red List data. External links open in a new tab.