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Lifespan, longevity, and ageing

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Maximum longevity: 23.4 years (captivity) Observations: It has been suggested that beavers may live as much as 50 years (Ronald Nowak 1999), which is doubtful. One captive specimen was still alive after 23.4 years (Richard Weigl 2005).
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Joao Pedro de Magalhaes
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Untitled

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One of the earliest accounts of beaver natural history was written by Samuel Hearne in the late 1700s. His journal entry on beavers is online at: http://web.idirect.com/~hland/sh/an020.htm.

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Behavior

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Beavers have a pair of anal scent glands, called castors, which secrete a musk-like substance called castoreum. This is used mainly for marking territories. The broad, flat, scaly tail is about 25 cm (about 10 in) long and serves as a warning signal when slapped against the water. Beavers also call out to others, making a low, groaning sound.

Communication Channels: visual ; acoustic ; chemical

Other Communication Modes: scent marks

Perception Channels: visual ; tactile ; acoustic ; chemical

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Conservation Status

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The conservation status differs with respect to source, but there have been significant threats to the survival of the beaver. Beavers have been hunted and trapped extensively in the past and by about 1900, the animals were almost gone in many of their original habitats. Pollution and habitat loss have also affected the survival of the beaver. In the last century, however, beavers have been successfully reintroduced to many of their former habitats.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Benefits

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Although beavers are beneficial to the environment, they can destroy it also. Dams slow the flow of water in fast streams, changing the flora and fauna and sometimes creating silting. They may flood low-lying areas, sometimes causing extensive loss of timber.

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Benefits

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Beaver fur has been a significant trade item for the last century, creating large amounts of money for merchants.

Beavers are incredibly beneficial to the environment. They are instrumental in creating habitats for many aquatic organisms, maintaining the water table at an appropriate level and controlling flooding and erosion, all by building dams. See the Sevilleta Long-Term Eocological Research Project (LTER)/ RKM and KVP-- University of New Mexico account on the web at http://sevilleta.unm.edu/animal/mammal/beaver.html for a more detailed explanation of the benefits of beavers in the environment.

Positive Impacts: body parts are source of valuable material

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Associations

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Beavers maintain wetlands that can slow the flow of floodwaters. They prevent erosion, and they raise the water table, which acts as a purifying system for the water. This happens because silt occurs upstream from dams, and toxins are then broken down. As ponds grow from water backed up by the damn, pond weeds and lilies take over. After beavers leave their homes, the dams decay, and meadows appears.

Ecosystem Impact: creates habitat; keystone species

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Trophic Strategy

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Beavers eat bark and cambium (the softer growing tissue under the bark of trees). Their favorites include willow, maple, poplar, beech, birch, alder, and aspen trees. They also eat water vegetation, as well as buds, and roots. Cellulose, which usually can not be digested by mammals, is a major component of their diet. Beavers have microorganisms in their cecum (a sac between the large and small intestine) that digest this material. In zoos, beavers are fed yams, lettuce, carrots and "rodent chow."

Plant Foods: leaves; roots and tubers; wood, bark, or stems

Primary Diet: herbivore (Lignivore)

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Distribution

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Beavers are found throughout all of North America except for the northern regions of Canada and the deserts of the southern United States and Mexico.

Biogeographic Regions: nearctic (Native )

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Habitat

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Beavers live in lodges, of which there are three types: those built on islands, those built on the banks of ponds, and those built on the shores of lakes. The island lodge consists of a central chamber, with its floor slightly above the water level, and with two entrances. One entrance opens up into the center of the hut floor, while the other is a more abrupt descent into the water.

The lodge, itself, is an oven-shaped house of sticks, grass, and moss, woven together and plastered with mud. Over the years, repair and elaboration leads to an increase in hut size. The room inside may measure 2.4 m (8 ft) wide and up to 1 m (3 ft) high. The floor is blanketed with bark, grass, and wood chips.

The pond lodge is built either a short way back from the edge of the bank, or partly hanging over it, with the front wall built up from the bottom of the pond. The lake lodge is built on the shelving shores of lakes. To ensure adequate water depth surrounding the lodge, beavers dam streams with logs, branches, mud, and stones.

Habitat Regions: temperate ; terrestrial ; freshwater

Terrestrial Biomes: forest

Aquatic Biomes: lakes and ponds; rivers and streams

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Life Expectancy

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Under favorable conditions, beavers will produce their first litters at two or three years of age. The average lifespan of a beaver in the wild is 10 to 20 years. While its size saves it from most predators, a beaver's lifespan can be cut short by predators, most commonly humans, wolves, and coyotes. Parasites and disease also play a factor in mortality.

Typical lifespan
Status: wild:
10 to 20 years.

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Morphology

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Beavers are primarily aquatic animals, and the largest rodents in North America. They have a waterproof, rich, glossy, reddish brown or blackish brown coat. The underhairs are much finer than the outer, protective, guard-hairs. The ears are short, round, and dark brown in coloration. A beaver's hind legs are longer than its front legs, thus making the rear end to be higher than the front end while walking.

Beaver skulls and teeth are disproportionately large. This is crucial for cutting through hard woods like maple and oak. Most noteably, the upper incisors, bright orange in color, are at least 5 mm wide and 20-25 mm long. These teeth grow throughout the animal's lifetime and are a necessity to survival, just as the animal's closable nostrils, closable ears, and transparent eye membranes are for aquatic existence.

Also notable are the anal and castor glands, found in both male and female beavers. Both sets of glands lie at the base of the tail, which is possibly the most defining characteristic of the beaver. It is broad, flat, and covered in large blackish scales. The anal and castor glands have been recorded as large as 3.4 by 2.2 inches for the castors, and 3.0 by 1 inch for the anal glands. Secretions from these glands are used in scent-marking, and give the beaver its odd odor.

Beavers also have anal and castor glands, which they use to mark their territory. These glands are located beneath the tail. A beaver's tail is broad, flat, and covered with large black scales.

Range mass: 13 to 32 kg.

Range length: 900 to 1170 mm.

Sexual Dimorphism: sexes alike

Other Physical Features: endothermic ; bilateral symmetry

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Associations

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Young beavers are very vulnerable, and are threatened by bears, wolves, wolverines, lynx, fishers and otters. An adult beaver's size is a deterrent to most predators, and though natural predators pose a very real danger to kits, man has proven to be, by far, the most dangerous predator to beavers. Killing beavers for their pelts, disrupting them through a change in habitat, and slowly poisoning them through pollution, which is known to infect wounds, all have lead to the threat which man poses on beavers.

Known Predators:

  • wolves (Canis lupus)
  • wolverines (Gulo gulo)
  • lynx (Lynx canadensis)
  • northern river otters (Lontra canadensis)
  • humans (Homo sapiens)
  • black bears and brown bears (Ursus)
  • fishers (Martes pennanti)
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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Reproduction

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Beavers are monogamous, but if one mate dies, the other will "remarry", or seek out a new mate. Beavers are driven away from their colonies usually around their second year of life, right before a new litter is born. They then make a colony of their own, usually several kilometers away, and they first breed around their third years of life, give or take a year depending on the quality of the environmtnt.

Mating System: monogamous

Male and female beavers are sexually mature at about 3 years of age. They mate between January and March in cold climates, and in late November or December in the south. Beavers give birth to one litter of kits per year, usually between April and June. The gestation period is about 3 months, or 105-107 days. During this time, the young develop inside the female's body. When they are born they are fully furred,have open eyes, and can swim within 24 hours. After several days they are also able to dive out of the lodge with their parents to explore the surrounding area.

Female beavers are sexually mature when they are about 3 years old. They give birth to one litter each year, usually between April and July. Baby beavers develop inside their mother for about 3 months. Baby beavers are called kits. When they are born they already have all of the fur and have their eyes open.

At birth kits are usually around 38 cm long including their tales. They tend to weigh from 250 to 600 grams and can be red, brown, or almost black. They remain in the lodge for a month, afterwards leaving for longer periods of time to swim and take in solid foods. Most beavers are weaned within two weeks, although it can take up to 90 days. The young usually stay with their parents for 2 years and then leave to make their own homes.

Breeding interval: Beavers breed once a year.

Breeding season: Mating takes place during the winter season, usually in January or February.

Range number of offspring: 1 to 4.

Average gestation period: 3 months.

Average weaning age: 2 weeks.

Average time to independence: 2 years.

Average age at sexual or reproductive maturity (female): 3 years.

Average age at sexual or reproductive maturity (male): 3 years.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

Average birth mass: 430 g.

Average gestation period: 128 days.

Average number of offspring: 3.5.

Average age at sexual or reproductive maturity (male)
Sex: male:
639 days.

Average age at sexual or reproductive maturity (female)
Sex: female:
639 days.

Parental care begins before birth, and continues for 1-2 years until the young have reached the stage of independence. In preparation for birth females will prepare a soft bed within the lodge. She then will use her flat tail as a sort of birthing mat. She will lick each kit clean, and nurse it. Both mother and father beaver play a part in providing food for the young and protecting them from predators.

Parental Investment: pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)

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Anderson, R. 2002. "Castor canadensis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Castor_canadensis.html
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Rebecca Anderson, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Associated Plant Communities

provided by Fire Effects Information System Animals
American beavers commonly inhabit riparian areas of mixed coniferous-deciduous
forests and deciduous forests containing abundant American beaver foods and lodge
building material such as quaking aspen (Populus tremuloides), willows
(Salix spp.), alders (Alnus spp.), red-osier dogwood (Cornus sericea),
and cottonwoods (Populus spp.) [2,25].
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Common Names

provided by Fire Effects Information System Animals
American beaver
Canadian beaver
beaver
flat-tail
bank beaver
castor
castor cat
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Cover Requirements

provided by Fire Effects Information System Animals
More info for the term: cover

The lodge is the major source of escape, resting, thermal, and
reproductive cover for American beavers. Lodges may be surrounded by water or
constructed against a bank. Water protects the lodge from predators and
provides concealment for American beavers when traveling to and from food
gathering areas and caches [2]. On lakes and ponds, lodges are
frequently situated in areas that provide shelter from wind, waves, and
ice [2]. Damming large streams with swift, turbulent waters creates
calm pools for feeding and resting [11].
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Distribution

provided by Fire Effects Information System Animals
More info for the term: tundra

The American beaver is found throughout most of North America except in the
Arctic tundra, peninsular Florida, and the Southwestern deserts
[2,31,35]. The distribution of six subspecies is listed below [10,19].
The distribution of the other seven was not found in the literature.

C. c. subsp. carolinensis - occurs in the southeastern part of the United
States north to southern Virginia, northern Ohio, Indiana, Illinois, and
west to southeastern Iowa, eastern Missouri, eastern Arkansas and
Louisiana [19].

C. c. subsp. taylori - occurs in northern Nevada in the streams and
tributaries of the Snake River drainage [10].

C. c. subsp. baileyi - occurs in the Humboldt River drainage [10].

C. c. subsp. repentinus - occurs along the Colorado River [10].

C. c. subsp. texensis - occurs in eastern Texas [10].

C. c. subsp. leucodenta - occurs along the Coast Ranges from California to
Alaska [10].
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Food Habits

provided by Fire Effects Information System Animals
More info for the terms: fresh, herbaceous, shrubs, tree

American beavers are herbivores. During late spring and summer their diet
consists mainly of fresh herbaceous matter [2,18]. American beavers appear to
prefer herbaceous vegetation over woody vegetation during all seasons if
it is available. Woody vegetation may be consumed during any season,
although its highest utilization occurs from late fall through early
spring when herbaceous vegetation is not available. The majority of the
branches and stems of woody vegetation are cached for later use during
the winter [2].

Winter is a critical period, especially for colonies on streams because
they must subsist solely on their winter food caches. In contrast with
stream American beavers, colonies on lakes are not solely dependent on their
stores of woody vegetation; they can augment their winter diet of bark
with aquatic plants [18].

Aquatic vegetation such as duck-potato (Sagittaria spp.), duckweed
(Lemma spp.), pondweed (Potamogeton spp.), and water weed (Elodea spp.)
are preferred foods when available [2]. The thick, fleshy rhizomes of
water lilies (Nymphaea spp. and Nuphar spp.) may be used as a food
source throughout the year. If present in sufficient amounts, water
lily rhizomes may provide an adequate winter food source, resulting in
little or no tree cutting or food caching of woody materials [2,18].
Other important winter foods of American beavers living on lakes include the
rhizomes of sedges and the rootstocks of mat-forming shrubs [18].

Important woody foods of American beavers include quaking aspen, willow,
cottonwood, alder, red maple (Acer rubrum), serviceberry (Amelanchier
spp.), mountain maple (Acer glabrum), red-osier dogwood, and green ash
(Fraxinus pennsylvanica) [2,18,22]. Other woody species occasionally
utilized for food include sugar maple (Acer saccharum), black ash
(Fraxinus nigra), yellow birch (Betula alleghaniensis), hazels (Corylus
spp.), hemlocks (Tsuga spp.), and Oregon crab apple (Malus fusca)
[18,21]. Aspen and willows are considered preferred American beaver foods;
however, these are generally riparian tree species and may be more
available for American beaver foraging but not necessarily preferred over all
other deciduous tree species. American beavers have been reported to subsist in
some areas by feeding on conifer trees; however, these trees are a poor
quality source of food [2].

Woody stems cut by American beavers are usually less than 3 to 4 inches (7.6-10.1
cm) in d.b.h. One study reported that trees of all size classes were
felled close to the water's edge, while only smaller diameter trees were
felled farther from the shore. Trees and shrubs closest to the water's
edge are generally utilized first [2].
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Habitat-related Fire Effects

provided by Fire Effects Information System Animals
More info for the terms: climax, forest, succession

Fire occurring in riparian areas often benefits American beaver populations [16].
American beavers are adapted to the early stages of forest succession. Quaking
aspen, willows, alders, and red-osier dogwood, prime American beaver food trees,
all sprout vigorously after fire. As succession progresses, these trees
become too large for American beavers to use or are replaced by climax trees
[34]. Recurring fires within parts of boreal forests have allowed aspen
and willow to replace coniferous forests. This change favors American beaver
populations, since both species are important food sources. Fire may
also help create more open bodies of water [16].
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Habitat: Cover Types

provided by Fire Effects Information System Animals
More info on this topic.

This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

16 Aspen
18 Paper birch
19 Gray birch - red maple
20 White pine - northern red oak - red maple
22 White pine - hemlock
24 Hemlock - yellow birch
25 Sugar maple - beech - yellow birch
26 Sugar maple - basswood
27 Sugar maple
28 Black cherry - maple
30 Red spruce - yellow birch
31 Red spruce - sugar maple - beech
35 Paper birch - red spruce - balsam fir
39 Black ash - American elm - red maple
57 Yellow-poplar
58 Yellow-poplar - eastern hemlock
59 Yellow-poplar - white oak - northern red oak
60 Beech - sugar maple
61 River birch - sycamore
62 Silver maple - American elm
63 Cottonwood
88 Willow oak - water oak - diamondleaf oak
93 Sugarberry - American elm - green ash
95 Black willow
96 Overcup oak - water hickory
108 Red maple
202 White spruce - paper birch
203 Balsam poplar
210 Interior Douglas-fir
212 Western larch
213 Grand fir
217 Aspen
221 Red alder
222 Black cottonwood - willow
229 Pacific Douglas-fir
230 Douglas-fir - western hemlock
235 Cottonwood - willow
243 Sierra Nevada mixed conifer
244 Pacific ponderosa pine - Douglas-fir
245 Pacific ponderosa pine
251 White spruce - aspen
252 Paper birch
254 Black spruce - paper birch
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Habitat: Ecosystem

provided by Fire Effects Information System Animals
More info on this topic.

This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

FRES11 Spruce-fir
FRES12 Longleaf-slash pine
FRES13 Loblolly-shortleaf pine
FRES14 Oak-pine
FRES15 Oak-hickory
FRES16 Oak-gum-cypress
FRES17 Elm-ash-cottonwood
FRES18 Maple-beech-birch
FRES19 Aspen-birch
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES22 Western white pine
FRES23 Fir-spruce
FRES25 Larch
FRES28 Western hardwoods
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Habitat: Plant Associations

provided by Fire Effects Information System Animals
More info on this topic.

This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the terms: bog, forest

K005 Mixed conifer forest
K011 Western ponderosa forest
K014 Grand fir - Douglas-fir forest
K016 Eastern ponderosa forest
K017 Black Hills pine forest
K018 Pine - Douglas-fir forest
K020 Spruce - fir - Douglas-fir forest
K021 Southwestern spruce - fir forest
K025 Alder - ash forest
K029 California mixed evergreen forest
K093 Great Lakes spruce - fir forest
K094 Conifer bog
K095 Great Lakes pine forest
K096 Northeastern spruce - fir forest
K098 Northern floodplain forest
K099 Maple - basswood forest
K100 Oak - hickory forest
K101 Elm - ash forest
K102 Beech - maple forest
K103 Mixed mesophytic forest
K106 Northern hardwoods
K107 Northern hardwoods - fir forest
K109 Transition between K104 and K106
K110 Northeastern oak - pine forest
K111 Oak - hickory - pine forest
K112 Southern mixed forest
K113 Southern floodplain forest
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Management Considerations

provided by Fire Effects Information System Animals
More info for the terms: cover, density, forest, natural, shrubs, succession, tree

American beavers will live in close proximity to humans if all habitat
requirements are met [27]. However, railways, roads, and land clearing
adjacent to waterways may affect American beaver habitat suitability. Transplants
of American beaver may be successful on strip mined land or in new impoundments
where water conditions are relatively stable. Highly acidic waters,
which often occur in strip-mined areas, are acceptable for American beaver if
suitable foods are present [2].

American beaver activity can have a significant influence on stream and riparian
habitats [3,14,24,30]. American beavers are the only mammals in North America
other than humans that can fell mature trees; therefore, their ability
to decrease forest biomass is much greater than that of other herbivores
[2]. Additionally, American beaver ponds conserve spring runoff, thus ensuring
more constant stream flow, diminishing floods, conserving soil, and
helping maintain the water table [12].

Through tree harvesting activity, American beavers can have an effect on natural
succession. According to Barnes and Dibble [3] tree cutting by American beavers
on the lower Chippewa River in west-central Wisconsin will alter the
course of succession on the riverbottom site studied. American beavers were
selective in their choice of woody plants, preferring ash (Fraxinus
spp.) and hickory (Carya spp.) over all other woody plants. These
authors predict a major reduction in density for future populations of
ash, hickory, and hackberry (Celtis spp.) in areas of American beaver activity
and an increase in the density of basswood (Tilia spp.) and elm (Ulmus
spp.) [3].

American beaver activity can be beneficial to some wildlife species [13,30].
Waterfowl often benefit from the increased edge, diversity, and
invertebrate communities created by American beaver activity [30]. Occupied
American beaver-influenced sites produce more waterfowl because of improved water
stability and increased brood-rearing cover; the production declines
with American beaver abandonment. Great-blue herons (Ardea herodias), ospreys
(Pandion halietus), bald eagles (Haliaeetus leucocephalus), kingfishers
(Ceryle alcyon), and many species of songbirds benefit from American beaver
activity as well. Otters, raccoons (Procyon lotor), mink, and muskrat
(Ondatra zibithica) thrive on the increased foraging areas produced by
American beaver activity. Berry-producing shrubs and brush in areas cut over by
American beavers attract white-tailed deer (Odocoileus virginianus) and black
bear (Ursus americanus) [30].

American beaver activity can also improve fish habitat. Production of three
trout species (Salomo spp. and Salvelines fontinalis) in a stream in the
Sierra Nevada increased due to a higher standing crop of invertebrates
in American beaver ponds [8]. Smallmouth bass (Micropterus dolomieuis) and
northern pike (Esok lucius) also benefit from American beaver impoundments [30].
In some instances American beaver ponds have provided up to six times the total
weight of salmonids per acre than that in adjacent stream habitat
without American beaver ponds [24]. In areas of marginal trout habitat, however,
American beaver activity can reduce trout production. American beaver-caused loss of
streamside shade and diminished water velocity can result in lethal
water temperatures [30].

The amount of influence that cattle have on riparian environment can be
reduced by American beaver activity in many valley bottoms. If American beavers are
thoroughly established in wide valley willow habitats prior to the
introduction of cattle, the immediate effect of cattle on the stream is
often minor [24].

American beaver activity can also have detrimental effects. American beaver-caused
flooding often kills valuable lowland timber [30]. Human/American beaver
conflicts occur when American beavers flood roadways and agricultural lands, and
dam culverts and irrigation systems. The economic cost of nuisance
American beaver activities often exceeds the value of their pelts and has been
estimated at $75 to $100 million annually in the United States.
Additionally, American beavers have potential to increase water-borne pathogens
(including Giardia lamblia) downstream from their activity [30].

American beavers are harvested for their pelts. In most states with substantial
American beaver populations, the species is now managed to provide a reliable
annual harvest and a relatively stable population [12].
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Occurrence in North America

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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Predators

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More info for the term: natural

American beavers have few natural predators. However, in certain areas, American beavers
may face predation pressure from wolves (Canis lupus), coyotes (Canis
latrans), lynx (Lynx canadensis), fishers (Martes pennanti), wolverines (Gulo
gulo), and occasionally bears (Ursus spp.). Alligators, minks (Mustela
vison), otters (Lutra canadensis), hawks, and owls periodically prey on
kits [19,22,27]. Humans kill American beavers for their fur [18,22].
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Preferred Habitat

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Suitable habitat for American beavers must contain all of the following: stable
aquatic habitat providing adequate water; channel gradient of less than
15 percent; and quality food species present in sufficient quantity [2].
American beavers can usually control water depth and stability on small streams,
ponds, and lakes. Large lakes or reservoirs (20 acres [8 ha] in surface
area) with irregular shorelines provide optimum habitat for the species.
Lakes and reservoirs that have extreme annual or seasonal fluctuations
in the water level are generally unsuitable habitat for American beavers [2,28].
Intermittent streams or streams that have major fluctuations in
discharge will have little year-round value as American beaver habitat [2].

Stream characteristics such as gradient, depth, and width are
determining factors in habitat use by American beaver [2,11]. Steep topography
prevents the establishment of a food transportation system [2].
Additionally, narrow valley bottoms cannot support the large amounts of
vegetation needed by American beavers. Consequently American beaver populations in narrow
valley bottoms are more cyclic than are populations in wider valley
bottoms [24]. Valleys less than 150 feet (46 m) wide are occupied less
frequently [2,24]. One study found that 68 percent of the American beaver
colonies recorded in Colorado were in valleys with a stream gradient of
less than 6 percent. No American beaver colonies were recorded in streams with a
gradient of 15 percent or more. Valleys that were only as wide as the
stream channel were unsuitable American beaver habitat, while valleys wider than
the stream channel were frequently occupied by American beavers [24].

Food availability is another factor determining suitable habitat for
American beavers [11]. Marshes, ponds, and lakes are often occupied by American beavers
when an adequate supply of food is available. American beavers generally forage
no more than about 300 feet (90 m) from water; however, foraging
distances of up to 656 feet (200 m) have been reported [2].
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Regional Distribution in the Western United States

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This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Taxonomy

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The currently accepted scientific name for the American beaver is Castor
canadensis Kuhl [6,10,19,22,33]. The subspecies differ in size,
proportion, color, and skull characteristics [10,33]. The following
subspecies have been mentioned in the literature [10,19,22,29,33]:

C. canadensis subsp. baileyi Nelson
C. canadensis subsp. belugae Taylor (Cook Inlet beaver)
C. canadensis subsp. canadensis Kuhl (Canadian beaver)
C. canadensis subsp. carolinensis Rhoads (Carolina beaver)
C. canadensis subsp. frondator Mearns (Sonora beaver)
C. canadensis subsp. leucodonta Gray (Pacific beaver)
C. canadensis subsp. mexicanus Bailey (Rio Grande beaver)
C. canadensis subsp. michiganensis Bailey (woods beaver)
C. canadensis subsp. pacificus Rhoads (Washington beaver)
C. canadensis subsp. phaeus Heller ( Admiralty beaver)
C. canadensis subsp. repentinus Goldman
C. canadensis subsp. taylori Davis
C. canadensis subsp. texensis Bailey (Texas beaver)
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Timing of Major Life History Events

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More info for the term: litter

Breeding season - Breeding occurs between January and March
[18,30,31,35]. American beavers are generally monogamous, although males will
mate with other females [22,31]. Only the colony's dominant female
breeds, producing one litter a year [30].

Gestation/litter - Gestation period lasts 4 months. Average litter size
varies between 2.3 and 4.1 [27,30,31,35]. Kits are weaned at 2 to 3
months and can swim by 1 week of age [31,35].

Age at sexual maturity - American beavers become sexually mature between age 2
and 3 [18,36].

Colony/dispersal - The colony consists of three age classes of American beavers:
the adults, the kits, and the yearlings born the previous spring
(average 5.1 American beavers per colony) [18]. After young American beavers reach their
second or third year, they are forced to leave the family group
[18,22,35]. Dispersal may be delayed in areas with high American beaver
densities. Subadults generally leave the natal colony in the late
winter or early spring [30]. Subadult American beavers have been reported to
migrate as far as 147 miles (236 km), although average migration
distances range from 5 to 10 miles (8-16 km) [2].

Life span - Up to 11 years in the wild, 15 to 21 years in
captivity [22,27].

The species is active throughout the year and is usually nocturnal.
Adult American beavers are nonmigratory [2].
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

Use of Fire in Population Management

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More info for the terms: fire regime, forest

Fire can be used to maintain American beaver habitat in a subclimax state, thus
ensuring adequate food supply for American beavers [16,26,34]. High American beaver
populations in many areas are the direct result of the extensive
clearcutting and forest fires which were characteristic of the northern
forests until recent years [25,34].

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".
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Tesky, Julie L. 1993. Castor canadensis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/

North American beaver

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The North American beaver (Castor canadensis) is one of two extant beaver species, along with the Eurasian beaver (Castor fiber).[22] It is native to North America and introduced in South America (Patagonia) and Europe (primarily Finland and Karelia). In the United States and Canada, the species is often referred to simply as "beaver", though this causes some confusion because another distantly related rodent, Aplodontia rufa, is often called the "mountain beaver". Other vernacular names, including American beaver[22] and Canadian beaver,[27] distinguish this species from the other extant beaver species, Castor fiber, which is native to Eurasia. The North American beaver is one of the official national wildlife of Canada symbols and is the official state mammal of Oregon and New York.[28]

Description

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North American beaver skeleton (Museum of Osteology)

The beaver is the largest rodent in North America and competes with its Eurasian counterpart, the European beaver, for being the second-largest in the world, both following the South American capybara. The European species is slightly larger on average but the American has a larger known maximum size. Adults usually weigh from 11 to 32 kg (24 to 71 lb), with 20 kg (44 lb) being typical. In New York, the average weight of adult male beavers was 18.9 kg (42 lb), while non-native females in Finland averaged 18.1 kg (40 lb). However, adults of both sexes averaged 16.8 kg (37 lb) in Ohio.[29][30][31] The species seems to conform to Bergmann's rule, as northern animals appear to be larger. In the Northwest Territory, adults weighed a median of 20.5 kg (45 lb).[32] The American beaver is slightly smaller in average body mass than the Eurasian species.[30] The head-and-body length of adult North American beavers is 74–90 cm (29–35 in), with the tail adding a further 20–35 cm (7.9–13.8 in). Very old individuals can exceptionally exceed normal sizes, weighing more than 40 kg (88 lb) or even as much as 50 kg (110 lb) (higher than the maximum known for the Eurasian beaver).[33][34][35][36]

Like the capybara, the beaver is semiaquatic. The beaver has many traits suited to this lifestyle. It has a large, flat, paddle-shaped tail and large, webbed hind feet. The unwebbed front paws are smaller, with claws. The forepaws are highly dextrous, and are used both for digging, and to fold individual leaves into their mouth and to rotate small, pencil-sized stems as they gnaw off bark.[37] The eyes are covered by a nictitating membrane which allows the beaver to see under water. The nostrils and ears are sealed while submerged. Their lips can be closed behind their front teeth so that they can continue to gnaw underwater.[38] A thick layer of fat under its skin insulates the beaver from its coldwater environment.

The beaver's fur consists of long, coarse outer hairs and short, fine inner hairs (see Double coat). The fur has a range of colors, but usually is dark brown. Scent glands near the genitals secrete an oily substance known as castoreum, which the beaver uses to waterproof its fur. There is also another set of oil glands producing unique chemical identifiers in the form of waxy esters and fatty acids.[37] The lush, workable fur was made into a number of products, most notably hats. Demand for furs for hats drove beavers nearly to the point of extinction, and the North American species was saved principally by a sudden change in style.

The beaver possesses continuously (or endlessly) growing incisors, and is a hindgut fermenter whose cecum, populated by symbiotic bacteria, helps to digest plant-based material. These traits are not unique to beavers, and are in fact present among all rodents.[39] Nonetheless, the beaver is remarkably specialized for the efficient digestion of its lignocellulose-heavy diet.[40]

Brain anatomy of the beaver is not particularly specialized for its semiaquatic life history. The brain masses of a beaver weighing 11.7 and 17 kg are 41 and 45 g respectively. C. canadensis has an encephalization quotient of 0.9 compared to other rodents; this is intermediate between similar terrestrial rodents and arboreal squirrels, and higher than similar aquatic terrestrial rodents, the muskrats and nutria. The cerebrum is well developed, and the neocortex comparatively large. Larger areas of the beaver's somatosensory cortex are dedicated to the processing of stimuli from the lips and the hands, more so than the tail and whiskers, which play a relatively minor role. The visual area of the brain is smaller than the gray squirrel.[38]

Distribution

Before their near-extirpation by trapping in North America, beavers were practically ubiquitous and lived from south of the arctic tundra to the deserts of northern Mexico, and from the Atlantic to the Pacific Oceans.[41][42][43] They are widely distributed in boreal and temperate ecoregions, where populations are rebounding from historic over-exploitation. Recently, beaver have been observed colonizing arctic tundra, likely as a result of climate-induced increases in riparian shrubs.[44][45][46]

Physician naturalist Edgar Alexander Mearns' 1907 report of beaver on the Sonora River may be the earliest report on the southernmost range of this North American aquatic mammal.[47] However, beavers have also been reported both historically and contemporarily in Mexico on the Colorado River, Bavispe River, and San Bernardino River in the Mexican states of Sonora and Chihuahua.[48][49][50]

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Skull of a North American Beaver found on San Francisco Bay shore

Behavior

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Beaver lodge, Ontario, Canada
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Beaver dam, northern California, USA
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Beavers use rocks for their dams when mud and branches are less available as seen on Bear Creek, a tributary to the Truckee River, in Alpine Meadows, California.

Beavers are active mainly at night. They are excellent swimmers and may remain submerged up to 15 minutes. More vulnerable on land, they tend to remain in the water as much as possible.[51] They use their flat, scaly tail both to signal danger by slapping the surface of the water and as a location for fat storage.

They construct their homes, or "lodges", out of sticks, twigs, rocks, and mud in lakes, streams, and tidal river deltas.[52] These lodges may be surrounded by water, or touching land, including burrows dug into river banks. Beavers are well known for building dams across streams and constructing their lodges in the artificial ponds which form. When building in a pond, the beavers first make a pile of sticks and then eat out one or more underwater entrances and two platforms above the water surface inside the pile. The first is used for drying off. Towards winter, the lodge is often plastered with mud which, when it freezes, has the consistency of concrete. A small air hole is left in the top of the lodge.

Dam-building

The purpose of the dam is to create deepwater refugia enabling the beaver to escape from predators. When deep water is already present in lakes, rivers, or larger streams, the beaver may dwell in a bank burrow and bank lodge with an underwater entrance. The beaver dam is constructed using branches from trees the beavers cut down, as well as rocks, grass, and mud. Where naturally-occurring woody material is limiting, beavers may build their dams largely of rocks.[53] The inner bark, twigs, shoots, and leaves of such trees are also an important part of the beaver's diet.[54] The trees are cut down using their strong incisor teeth. Their front paws are used for digging and carrying and placing materials. The sound of running water dictates when and where a beaver builds its dam. Besides providing a safe home for the beaver, beaver ponds also provide habitat for waterfowl, fish, and other aquatic animals. Their dams help reduce soil erosion and can help reduce flooding. However, beaver dams are not permanent and depend on the beavers' continued presence for their maintenance. Beavers generally concentrate on building and repairing dams in the fall in preparation for the coming winter. In northern areas, they often do not repair breaches in the dam made by otters, and sometimes breach the dam themselves and lower the water level in the pond to create more breathing space under the ice or get easier access to trees below the dam. In a 1988 study in Alberta, Canada, no beavers repaired "sites of water loss" during the winter. Of 178 sites of water loss, beavers repaired 78 when water was opened, and did not repair 68. The rest were partially repaired.[55]

Beavers are best known for their dam-building. They maintain their pond-habitat by reacting quickly to the sound of running water, and damming it up with tree branches and mud. Early ecologists believed that this dam-building was an amazing feat of architectural planning, indicative of the beaver's high intellect. This theory was tested when a recording of running water was played in a field near a beaver pond. Although it was on dry land, the beaver covered the tape player with branches and mud.[56] The largest beaver dam is 2,790 ft (850 m) in length—more than half a mile long—and was discovered via satellite imagery in 2007.[57] It is located on the southern edge of Wood Buffalo National Park in northern Alberta and is more than twice the width of the Hoover Dam which spans 1,244 ft (379 m).[58][59]

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C. c. canadensis, feeding in winter

Normally, the purpose of the dam is to provide water around their lodges that is deep enough that it does not freeze solid in winter. The dams also flood areas of surrounding forest, giving the beaver safe access to an important food supply, which is the leaves, buds, and inner bark of growing trees. In colder climates where their pond freezes over, beavers also build a food cache from this food resource.[37] To form the cache, beavers collect food in late fall in the form of tree branches, storing them under water (usually by sticking the sharp chewed base of the branches into the mud on the pond bottom), where they can be accessed through the winter. Often, the pile of food branches projects above the pond and collects snow. This insulates the water below it and keeps the pond open at that location.[60] The frozen combination of branches and ice is known as a cap, sealing the food cache. Beavers often maintain an underwater entrance to their dam, and they can access their food cache from their lodge by swimming under the ice. In warmer climes, a winter food store is less common.[37]

Muskrats have been thought to steal food from beaver lodges, but seemingly cooperative relationships exist, with beavers allowing muskrats to reside in their lodge if they gather fresh reeds.[61]

Canals

Another component to the beaver's habitat is the canal. Canals are used to float logs to a pond, and dams may also be used to maintain the water levels in these canals. Several land trails can extend from the canals.[62] Despite being widespread in some beaver-inhabited areas, beaver canals and their environmental effects are much less studied than beaver dams. Beaver primarily develop canals to increase accessibility of river resources, facilitate transport of acquired resources, and to decrease the risk of predation. Beaver canals can be over 0.5 km in length.[63] Beavers build canals by pushing through soil and vegetation using their forelimbs.

It has been hypothesized that beavers' canals are not only transportation routes to extend foraging, but also an extension of their "central place" around the lodge and/or food cache. A 2012 study of beavers' mark on the landscape found that cut stumps were negatively related to distance from beaver canals, but not to the central body of water. This finding suggested that beavers may consider the canals to be part of their "central place" as far as foraging activity is concerned.[64]

Social behavior

Communication is highly developed in beaver, including scent marking, vocalization, and tail slapping. Beaver deposit castoreum on piles of debris and mud called scent mounds, which are usually placed on or near lodges, dams, and trails less than a meter from water. Over 100 of such mounds can be constructed within one territory.[37] Beaver colonies with close neighbors constructed more "scent mounds" than did isolated colonies, and the number of scent mounds at each active lodge is correlated with the distance to the nearest occupied lodge.[65]

Although seven vocal sounds have been described for beaver, most zoologists recognize only three: a whine, hiss, and growl. Vocalizations and tail slapping may be used to beg for food, signal to family members to warn of predators, or to drive away or elicit a response from predators.

Beavers usually mate for life, forming familial colonies. Beaver "kits" are born precocious and with a developed coat. The young beaver "kits" typically remain with their parents up to two years. Kits express some adult behaviors, but require a long period in the family to develop their dam construction skills, and other abilities required for independent life.[37]

Diet

Beaver are herbivorous generalists with sophisticated foraging preferences. Beavers consume a mix of herbaceous and woody plants, which varies considerably in both composition and species diversity by region and season.[37] They prefer aspen and poplar, but also take birch, maple, willow, alder, black cherry, red oak, beech, ash, hornbeam, and occasionally pine and spruce.[60] They also eat cattails, water lilies, and other aquatic vegetation, especially in the early spring. Contrary to widespread belief, they do not eat fish.[66]

Beavers select food based on taste, coarse physical shape, and odor. Beavers feed on wood, bark, branches, twigs, leaves, stems, sprouts, and in some cases, the sap and storax of pine and sweetgum.[37]

When herbaceous plants are actively growing, they make up much of the beaver's diet. In the winter, beavers switch to woody plants and the food they have stored over the winter. The protein to calorie ratio of a beaver's diet is 40 mg/calorie in summer and 8 mg/calorie for the rest of the year. In northern latitudes, the water lilies Nymphaea and Nuphar are the most important herbaceous component. The rhizomes are stored in the food cache and remain actively growing.[37]

Willow is an important protein source and is likely to be available for the longest period of time in a beaver's habitat especially in the far north. When available, aspen and poplar are preferred over willow. Conifers are also cut or gnawed by beavers, and used for food and/or building material.

Beavers do not necessarily use the same trees as construction material and as food. Inedible material is more likely to be used as the cap of a beaver family's food cache, the upper part which is frozen in the ice, while the cache itself is composed of edible, high quality branches, which remain unfrozen and accessible.[37]

Beavers avoid red maple, which can be the only tree left standing at the edges of some beaver ponds.[37][67]

The beaver's gut microbiome is complex and specialized for a wood-heavy diet, sharing a number of similarities with other mammalian herbivores. However the microbial community in the beaver shows less taxonomic diversity than the "typical" mammalian gut. The major OTUs are Bacteroidetes and Firmicutes.[40]

Predators

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Brooklyn Museum – American Beaver – John J. Audubon

Common natural predators include coyotes, wolves, and mountain lions.[68] American black bears may also prey on beavers if the opportunity arises, often by smashing their paws into the beavers' lodges.[69][70][71] Perhaps due to differing habitat preferences, brown bears were not known to hunt beavers in Denali National Park.[72] Less significant predators include wolverines, which may attack a rare beaver of up to adult size, and Canadian lynx, bobcats, and foxes, predators of kits or very sick or injured animals rather than full-grown beavers due to their increasingly smaller size. American alligators, which only minimally co-exist in the wild with beavers, also seldomly threaten them. Both golden eagles (Aquila chrysaetos) and bald eagles (Haliaeetus leucocephalus) may on occasion prey on a beaver, most likely only small kits.[73] Despite repeated claims, no evidence shows that North American river otters are typically predators of beavers but anecdotally may take a rare beaver kit.[74]

Reproduction

North American beavers have one litter per year, coming into estrus for only 12 to 24 hours, between late December and May but peaking in January. Unlike most other rodents, beaver pairs are monogamous, staying together for multiple breeding seasons. Gestation averages 128 days and they have a range of three to six kits per litter (usually 4-5).[75] Most beavers do not reproduce until they are three years of age, but about 20% of two-year-old females reproduce.[76]

Subspecies

The first fossil records of beaver are 10 to 12 million years old in Germany, and they are thought to have migrated to North America across the Bering Strait. The oldest fossil record of beavers in North America are of two beaver teeth near Dayville, Oregon, and are 7 million years old.[77]

At one time, 25 subspecies of beavers were identified in North America, with distinctions based primarily on slight morphological differences and geographical isolation at the time of discovery. However, modern techniques generally use genetics rather than morphology to distinguish between subspecies, and currently the Integrated Taxonomic Information System (which provides authoritative[78] taxonomic information on plants, animals, fungi, and microbes of North America and the world) does not recognize any subspecies of C. canadensis, though a definitive genetic analysis has not been performed. Such an analysis would be complicated by the fact that substantial genetic mixing of populations has occurred because of the numerous reintroduction efforts intended to help the species recover following extirpation from many regions.

The most widespread (formerly recognized) subspecies, which perhaps are now best thought of as populations with some distinct physical characteristics, are C. c. acadicus (New England beaver), C. c. canadensis (Canadian beaver), C. c. carolinensis (Carolina beaver), and C. c. missouriensis (Missouri River beaver).[79] The Canadian beaver originally inhabited almost all of the forested area of Canada,[80] and because of its more valued fur, was often selected for reintroductions elsewhere. The Carolina beaver is found in the southeastern United States; the Missouri River beaver, as its name suggests, is found in the Missouri River and its tributaries; and C. c. acadicus is found throughout the New England area in the northeastern United States.

Differences from European beaver

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Skulls of a European and Canadian beaver.

Although North American beavers are superficially similar to the European beaver (Castor fiber), several important differences exist between the two species. North American beavers tend to be slightly smaller, with smaller, more rounded heads; shorter, wider muzzles; thicker, longer, and darker underfur; wider, more oval-shaped tails; and longer shin bones, allowing them a greater range of bipedal locomotion than the European species. North American beavers have shorter nasal bones than their European relatives, with the widest point being at the middle of the snout for the former, and in the tip for the latter. The nasal opening for the North American species is square, unlike that of the European race, which is triangular. The foramen magnum is triangular in the North American beaver, and rounded in the European. The anal glands of the North American beaver are smaller and thick-walled with a small internal volume compared to that of the European species. Finally, the guard hairs of the North American beaver have a shorter hollow medulla at their tips. Fur color is also different. Overall, 50% of North American beavers have pale brown fur, 25% are reddish brown, 20% are brown, and 6% are blackish, while in European beavers, 66% have pale brown or beige fur, 20% are reddish brown, nearly 8% are brown, and only 4% have blackish coats.[81]

The two species are not genetically compatible. North American beavers have 40 chromosomes, while European beavers have 48. Also, more than 27 attempts were made in Russia to hybridize the two species, with one breeding between a male North American beaver and a female European resulting in one stillborn kit. These factors make interspecific breeding unlikely in areas where the two species' ranges overlap.[81]

Ecology

The beaver was trapped out and almost extirpated in North America because its fur and castoreum were highly sought after.[42] The beaver furs were used to make clothing and beaver hats. In the United States, extensive trapping began in the early 17th century, with more than 10,000 beaver per year taken for the fur trade in Connecticut and Massachusetts between 1620 and 1630.[82] From 1630 to 1640, around 80,000 beavers were taken annually from the Hudson River and western New York.[83] From 1670 onwards, the Hudson's Bay Company sent two or three trading ships into the bay every year to take furs to England from Canada. Archaeological and historical evidence suggests that beaver ponds created "moth-hole like" habitats in the deciduous forest that dominated eastern North America. This nonforest habitat attracted both Native American and early colonial hunters to the abundant fish, waterfowl, and large game attracted to the riparian clearings created by these aquatic mammals. The first colonial farmers were also attracted to the fertile, flat bottomlands created by the accumulated silt and organic matter in beaver ponds.[84]

As eastern beaver populations were depleted, English, French, and American trappers pushed west. Much of the westward expansion and exploration of North America was driven by the quest for this animal's fur. Before the 1849 California Gold Rush, an earlier, 19th-century California Fur Rush drove the earliest American settlement in that state. During the roughly 30 years (1806–1838) of the era of the mountain man, the West from Missouri to California and from Canada to Mexico was thoroughly explored and the beaver was brought to the brink of extinction.

With protection in the late 19th and early 20th centuries, the current beaver population has rebounded to an estimated 10 to 15 million; this is a fraction of the originally estimated 100 to 200 million North American beavers before the days of the fur trade.[85][86]

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A wire mesh fence installed around a tree trunk in Toronto. Wire mesh fences are used in an attempt to prevent beavers' damage.[87]

These animals are considered pests in parts of their range because their dams can cause flooding, or because their habit of felling trees can pose danger to people, as in Charlotte, North Carolina's Park Road Park.[88] Because they are persistent in repairing damage to the dam, they were historically relocated or exterminated. Nonlethal methods of containing beaver-related flooding have been developed.[89] One such flow device has been used by both the Canadian and U.S. governments, called "beaver deceivers" or levelers, invented and pioneered by wildlife biologist Skip Lisle.[90]

The beaver is a keystone species, increasing biodiversity in its territory through creation of ponds and wetlands.[91] As wetlands are formed and riparian habitats enlarged, aquatic plants colonize newly available watery habitat. Insect, invertebrate, fish, mammal, and bird diversities are also expanded.[92] Effects of beaver recolonization on native and non-native species in streams where they have been historically absent, particularly dryland streams, is not well-researched.[93]

Relationship with humans

As introduced non-native species

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Beaver damage on the north shore of Robalo Lake, Navarino Island, Chile

In the 1940s, beavers were brought to Tierra del Fuego in southern Chile and Argentina for commercial fur production and introduced near Fagnano Lake. Although the fur enterprise failed, 25 mating pairs of beavers were released into the wild. Having no natural predators in their new environment, they quickly spread throughout the main island, and to other islands in the archipelago, reaching a number of 100,000 individuals within just 50 years. Although they have been considered an invasive species, it has been more recently shown that the beaver have some beneficial ecological effects on native fish and should not be considered wholly detrimental.[94] Although the dominant Lenga beech (Nothofagus pumilio) forest can regenerate from stumps, most of the newly created beaver wetlands are being colonized by the rarer native Antarctic beech (Nothofagus antarctica). It is not known whether the shrubbier Antarctic beech will be succeeded by the originally dominant and larger Lengo beech, however, and the beaver wetlands are readily colonized by non-native plant species.[94] In contrast, areas with introduced beaver were associated with increased populations of the native catadromous puye fish (Galaxias maculatus).[95][96] Furthermore, the beavers did not seem to have a highly beneficial impact on the exotic brook trout (Salvelinus fontinalis) and rainbow trout (Oncorhynchus mykiss) which have negative impacts on native stream fishes in the Cape Horn Biosphere Reserve, Chile.[96] They have also been found to cross saltwater to islands northward; and reached the Chilean mainland in the 1990s.[97] On balance, because of their landscape-wide modifications to the Fuegian environment and because biologists want to preserve the unique biota of the region, most favor their removal.[98]

North American beavers were released in Finland in 1937, before it was realized that they formed a separate species; following this, 7 beavers expanded to a population of 12,000 within 64 years.[99] Eurasian beavers had earlier been extirpated from the region, so the release was intended as a reintroduction project.[100] By 1999, it was estimated that 90% of beavers in Finland were the American species. However, the species is not always considered invasive, as in Europe it has a similar keystone effect to European beavers, which have not recolonized the area. The beaver population has been controlled by issuing hunting licenses.[101] A report in 2010 concluded that while the current population of American beavers was not problematic, as the species has larger litters than European beavers and builds somewhat larger dams, it could become a problem if its range continues expanding into Russia, but this does not seem to be taking place.[102]

In Europe, significant invasive populations of Canadian beaver are only present in Finland and Karelia, as the boundary between species has somewhat stabilized, but smaller occurrences have been detected elsewhere.[100] Ephemeral populations of C. canadensis in Germany and Poland were found from the 1950s to 1970s. Zoo escapes in 2006 created a small population of invasive C. canadensis in Luxembourg, Rhineland-Palatinate and Belgium.[99] American beavers have not been detected in Sweden, Norway, or Denmark.[102]

As food

Beaver meat is similar tasting to lean beef, but care must be taken to prevent contamination from the animal's strong castor (musk) gland. It is usually slow-cooked in a broth, and was a valuable food source to Native Americans. Early French Canadian Catholics considered beaver to be "four-legged fish" that could be eaten at Lent.[103]

Symbolism

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Beaver sculpture over entrance to Canadian Parliament Building

As one of the national symbols of Canada,[104] the North American beaver is depicted on the Canadian nickel.[104] This beaver was also featured on the first Canadian postage stamp, the Three Penny Beaver, which is considered the first postage stamp to show an animal instead of a head of state.[105] It is also the state animal of Oregon and New York of the United States, and a common school emblem for engineering schools, including the California Institute of Technology, the Massachusetts Institute of Technology, and the University of Alberta as well as the mascot for Oregon State University, Babson College, and the City College of New York. A beaver is featured prominently on the stamp and seal issued to Professional Engineers and Geoscientists by APEGA. It also appears on the back on the state flag of Oregon. The beaver also appears in the coats of arms of the Hudson's Bay Company,[106] University of Toronto, Wilfrid Laurier University, and the London School of Economics.

Busy beaver is a term in theoretical computer science which refers to a terminating program of a given size that produces the most output possible.

Much of the early economy of New Netherland was based on the beaver fur trade. As such, the seal of New Netherland featured the beaver; likewise, the coats of arms of Albany, New York and New York City included the beaver.

See also

References

  1. ^ Cassola, F. (2016). "Castor canadensis". IUCN Red List of Threatened Species. 2016: e.T4003A22187946. doi:10.2305/IUCN.UK.2016-3.RLTS.T4003A22187946.en.CS1 maint: uses authors parameter (link)
  2. ^ a b Kuhl, Heinrich (1820). "Castor Canadensis". Beiträge zur Zoologie und vergleichenden Anatomie. Frankfurt: Verlag der Hermannschen Buchhandlung. pp. 64–65.
  3. ^ a b Bailey, Vernon; Doutt, J. Kenneth (1942). "Two New Beavers from Labrador and New Brunswick". Journal of Mammalogy. 23 (1): 86–88. doi:10.2307/1374859. JSTOR 1374859.
  4. ^ Nelson, E. W. (1927). "Description of a New Subspecies of Beaver". Proceedings of the Biological Society of Washington. 40: 125–126.
  5. ^ a b Taylor, Walter P. (1916). "The Status of the Beavers of Western North America, with a Consideration of the Factors in their Speciation". University of California Publications in Zoology. 12 (15): 413–495.
  6. ^ Allen, Glover M. (1942). "Newfoundland Beaver". Extinct and Vanishing Mammals of the Western Hemisphere, with the Marine Species of All the Oceans. American Committee for International Wild Life Protection. pp. 62–63.
  7. ^ a b Rhoads, Samuel N. (1898). "Contributions to a Revision of the North American Beavers, Otters and Fishers". Transactions of the American Philosophical Society. New Ser. 19 (3): 417–439. doi:10.2307/1005498. hdl:2027/hvd.32044107349482. JSTOR 1005498.
  8. ^ Warren, Edward R.; Hall, E. Raymond (1939). "A New Subspecies of Beaver from Colorado". Journal of Mammalogy. 20 (3): 358–362. doi:10.2307/1374265. JSTOR 1374265.
  9. ^ a b c Durrant, Stephen D.; Crane, Harold (1948). "Three New Beavers from Utah". University of Kansas Publications, Museum of Natural History. 1 (20): 407–417.
  10. ^ Mearns, Edgar A. (1898). "Preliminary Diagnoses of New Mammals of the Genera Sciurus, Castor, Neotoma, and Sigmodon, from the Mexican Border of the United States". Proceedings of the United States National Museum. 20 (1132): 502–503. doi:10.5479/si.00963801.1132.501.
  11. ^ Jewett, S. G.; Hall, E. R. (1940). "A New Race of Beaver from Oregon". Journal of Mammalogy. 21 (1): 87–89. doi:10.2307/1374665. JSTOR 1374665.
  12. ^ Gray, J. E. (1869). "On the White-toothed American Beaver". The Annals and Magazine of Natural History. 4th Ser. 4 (22): 293. doi:10.1080/00222936908696055.
  13. ^ a b Bailey, Vernon (1913). "Two New Subspecies of North American Beavers". Proceedings of the Biological Society of Washington. 26: 191–194.
  14. ^ Bailey, V. (1919). "A New Subspecies of Beaver from North Dakota". Journal of Mammalogy. 1 (1): 31–32. doi:10.1093/jmammal/1.1.31. JSTOR 1373717.
  15. ^ Heller, Edmund (1909). "The Mammals". University of California Publications in Zoology. 5 (2, Birds and Mammals of the 1907 Alexander Expedition to Southeastern Alaska): 250–255.
  16. ^ Goldman, E. A. (1932). "A New Beaver from Arizona". Journal of Mammalogy. 13 (3): 266–267. doi:10.2307/1374004. JSTOR 1374004.
  17. ^ Benson, Seth B. (1933). "A New Race of Beaver from British Columbia". Journal of Mammalogy. 14 (4): 320–325. doi:10.2307/1373950. JSTOR 1373950.
  18. ^ Taylor, Walter P. (1912). "The Beaver of West Central California". University of California Publications in Zoology. 10 (7): 167–169.
  19. ^ Grinnell, Joseph (1933). "Review of the Recent Mammal Fauna of California". University of California Publications in Zoology. 40 (2): 166.
  20. ^ Davis, William B. (1939). The Recent Mammals of Idaho. Caldwell, ID: Caxton. p. 273.
  21. ^ Bailey, Vernon (1905). "Castor canadensis texensis subsp. nov. Texas Beaver". Biological Survey of Texas. North American Fauna. 25. Washington: Government Printing Office. pp. 122–125.
  22. ^ a b c Helgen, K.M. (2005). "Family Castoridae". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 842. ISBN 978-0-8018-8221-0. OCLC 62265494.
  23. ^ Warner, Richard E. and Hendrix, Kathleen M. (eds.) (1984). California Riparian Systems: Ecology, Conservation, and Productive Management University of California Press, p. 952. Retrieved August 4, 2007.
  24. ^ Browse Genus equals Castor by Scientific Name for All Museums Archived June 14, 2007, at the Wayback Machine. Berkeley Natural History Museums. Retrieved August 4, 2007.
  25. ^ Tesky, Julie L. (1993) Wildlife Species: Castor canadensis Fire Effects Information System (Online), U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Retrieved August 4, 2007.
  26. ^ Jenkins, Stephen H.; Busher, Peter E. (1979). "Castor canadensis". Mammalian Species. 120 (120): 1–8. doi:10.2307/3503787. JSTOR 3503787.
  27. ^ Invasive Species Specialist Group (ISSG) (2006). "Castor canadensis (mammal)". Global Invasive Species Database (GISD). IUCN Species Survival Commission. Retrieved July 16, 2009: "Common names: American beaver (English), beaver (English), Canadian beaver, castor (French), castor americano (Spanish), North American beaver (English)"CS1 maint: postscript (link)
  28. ^ Official symbols of Canada Archived June 24, 2016, at the Wayback Machine. Government of Canada
  29. ^ Müller-Schwarze, D., & Schulte, B. A. (1999). Behavioral and ecological characteristics of a "climax" population of beaver (Castor canadensis). In Beaver protection, management, and utilization in Europe and North America (pp. 161–177). Springer US.
  30. ^ a b Lahti, S., & Helminen, M. (1974). The beaver Castor fiber (L.) and Castor canadensis (Kuhl) in Finland. Acta Theriologica, 19(13), 177–189.
  31. ^ Svendsen G. E. (1989). "Pair formation, duration of pair-bonds, and mate replacement in a population of beavers (Castor canadensis)". Canadian Journal of Zoology. 67 (2): 336–340. doi:10.1139/z89-049.
  32. ^ Aleksiuk M., Cowan I. M. (1969). "Aspects of seasonal energy expenditure in the beaver (Castor canadensis Kuhl) at the northern limit of its distribution". Canadian Journal of Zoology. 47 (4): 471–481. doi:10.1139/z69-086.
  33. ^ "Home Page, Alaska Department of Fish and Game". Adfg.state.ak.us. Retrieved March 16, 2013.
  34. ^ The Beaver – Life Tracks. Timberwolfinformation.org
  35. ^ Burnie D and Wilson DE (Eds.), Animal: The Definitive Visual Guide to the World's Wildlife. DK Adult (2005), ISBN 0789477645
  36. ^ Boyle, Steve and Owens, Stephanie (February 6, 2007) North American Beaver (Castor canadensis): A Technical Conservation Assessment. USDA Forest Service, Rocky Mountain Region
  37. ^ a b c d e f g h i j k Baker, B.W.; Hill, E.P. (2003). Feldhammer; Thompson; Chapman (eds.). "Beaver (Castor canadensis)" (PDF). Wild Mammals of North America: Biology, Management, and Conservation (Second ed.). Baltimore, Maryland, USA: The Johns Hopkins University Press: 288–310 – via USDA APHIS.
  38. ^ a b Müller-Schwarze, Dietland; Sun, Lixing (2003). The beaver : natural history of a wetlands engineer. Cornell University Press. pp. 10–11. ISBN 0-8014-4098-X. OCLC 977989893.
  39. ^ "Dental Anatomy of Rodents". www.vivo.colostate.edu. Retrieved February 21, 2020.
  40. ^ a b Gruninger, Robert J.; McAllister, Tim A.; Forster, Robert J. (May 26, 2016). "Bacterial and Archaeal Diversity in the Gastrointestinal Tract of the North American Beaver (Castor canadensis)". PLOS ONE. 11 (5): e0156457. doi:10.1371/journal.pone.0156457. ISSN 1932-6203. PMC 4881982. PMID 27227334.
  41. ^ Morgan, Lewis H. (1868). The American Beaver and his Works. J. B. Lippincott & Co. p. 32.
  42. ^ a b Naiman, Robert J.; Johnston, Carol A. & Kelley, James C. (December 1988). "Alteration of North American Streams by Beaver" (PDF). BioScience. 38 (11): 753–762. doi:10.2307/1310784. JSTOR 1310784. Archived from the original (PDF) on March 4, 2012. Retrieved February 28, 2010.
  43. ^ Christopher W. Lanman; Kate Lundquist; Heidi Perryman; J. Eli Asarian; Brock Dolman; Richard B. Lanman; Michael M. Pollock (2013). "The historical range of beaver (Castor canadensis) in coastal California: an updated review of the evidence". California Fish and Game. 99 (4): 193–221. Retrieved September 27, 2016.
  44. ^ Jung, Thomas S.; Frandsen, Jay; Gordon, Danny C.; Mossop, David H. (2016). "Colonization of the Beaufort Coastal Plain by beaver (Castor canadensis): a response to shrubification of the tundra?". Canadian Field-Naturalist. 130 (4): 332–335. doi:10.22621/cfn.v130i4.1927. ISSN 0008-3550.
  45. ^ Tape, Ken D.; Jones, Benjamin M.; Arp, Christopher D.; Nitze, Ingmar; Grosse, Guido (2018). "Tundra be dammed: Beaver colonization of the Arctic". Global Change Biology. 24 (10): 4478–4488. doi:10.1111/gcb.14332. ISSN 1365-2486. PMID 29845698.
  46. ^ Jones, Benjamin M; Tape, Ken D; Clark, Jason A; Nitze, Ingmar; Grosse, Guido; Disbrow, Jeff (2020). "Increase in beaver dams controls surface water and thermokarst dynamics in an Arctic tundra region, Baldwin Peninsula, northwestern Alaska". Environmental Research Letters. 15 (7): 075005. doi:10.1088/1748-9326/ab80f1. ISSN 1748-9326.
  47. ^ Mearns, Edgar Alexander (1907). Mammals of the Mexican boundary of the United States: A descriptive catalogue of the species of mammals occurring in that region; with a general summary of the natural history, and a list of trees. Government Printing Office. p. 359.
  48. ^ Gallo-Reynoso, Juan-Pablo; Suarez-Gracida, Gabriela; Cabrera-Santiago, Horacia; Coria-Galindo, Else; Egido-Villarreal, Janitzio & Ortiz, Leo C. (2002). "Status of Beavers (Castor canadensis frontador) in Rio Bavispe, Sonora, Mexico". The Southwestern Naturalist. 47 (3): 501. doi:10.2307/3672516. JSTOR 3672516. Retrieved November 25, 2011.
  49. ^ Karla Pelz Serrano; Eduardo Ponce Guevara; Carlos A. López González. "Habitat and Conservation Status of the Beaver in the Sierra San Luis Sonora, México" (PDF). USDA Forest Service Proceedings RMRS-P-36. Retrieved December 5, 2017.
  50. ^ El Heraldo de Chihuahua (December 5, 2017). "Nice surprise: camera discovers that there are otters in Chihuahua". El Sol de Mexico.
  51. ^ "World Book". www.worldbookonline.com. Retrieved June 16, 2019.
  52. ^ Mapes, Lynda V. (May 18, 2009). "Scientist discovers beavers building prime salmon habitat in Skagit Delta". The Seattle Times. Retrieved June 22, 2010.
  53. ^ Jung, Thomas S.; Staniforth, Jennifer A. (2010). "Unusual beaver, Castor canadensis, dams in central Yukon". Canadian Field-Naturalist. 124 (3): 274–275. doi:10.22621/cfn.v124i3.1090. ISSN 0008-3550.
  54. ^ Gallant, D.; Bérubé, C.H.; Tremblay, E. & Vasseur, L. (2004). "An extensive study of the foraging ecology of beavers (Castor canadensis) in relation to habitat quality" (PDF). Canadian Journal of Zoology. 82 (6): 922–933. doi:10.1139/z04-067. Retrieved May 4, 2010.
  55. ^ Donald G. Reid, Stephen M. Herrero and Thomas E. Code, "River Otters as Agents of Water Loss from Beaver Ponds," Journal of Mammalogy, February 1988.
  56. ^ Richard P.B. (1983). "Mechanisms and adaptation in the constructive behavior of the beaver (C. fiber L.)". Acta Zoologica Fennica. 174: 105–108.
  57. ^ Thie, Jean. "National Geographic photos". Geostrategis.com. Retrieved March 16, 2013.
  58. ^ "Longest beaver dam". Guinness World Records. Retrieved December 2, 2020.
  59. ^ "World's Largest Beaver Dam". Atlas Obscura. Retrieved December 2, 2020.
  60. ^ a b Müller-Schwarze, Dietland & Sun, Lixing (2003). The Beaver: Natural History of a Wetlands Engineer. Cornell University Press. pp. 67–75. ISBN 978-0-8014-4098-4.
  61. ^ Beaver Lodge Construction Squad | Attenborough | BBC Earth, retrieved December 8, 2019
  62. ^ "Comparative Mammalian Brain Collections: North American beaver (Castor canadensis)". neurosciencelibrary.org. Retrieved March 8, 2020.
  63. ^ Grudzinski, Bartosz P.; Cummins, Hays; Vang, Teng Keng (September 15, 2019). "Beaver canals and their environmental effects". Progress in Physical Geography: Earth and Environment. 44 (2): 189–211. doi:10.1177/0309133319873116. ISSN 0309-1333. S2CID 204257682.
  64. ^ Abbott, Matthew; Fultz, Brandon; Wilson, Jon; Nicholson, Jody; Black, Matt; Thomas, Adam; Kot, Amanda; Burrows, Mallory; Schaffer, Benton; Benson, David (January 1, 2012). "Beaver-Dredged Canals and their Spacial Relationship to Beaver-Cut Stumps". Proceedings of the Indiana Academy of Science (Vol.121, No.2).
  65. ^ Müller-Schwarze, D.; Heckman, Susan (January 1, 1980). "The social role of scent marking in beaver (Castor Canadensis)". Journal of Chemical Ecology. 6 (1): 81–95. doi:10.1007/BF00987529. ISSN 1573-1561. S2CID 43315636.
  66. ^ Young, Mary Taylor (August 13, 2007). "Colorado Division of Wildlife: Do Beavers Eat Fish?". Archived from the original on September 10, 2010. Retrieved May 18, 2015. wildlife.state.co.us
  67. ^ Müller-Schwarze, D.; Schulte, B. A.; Sun, L.; Müller-Schwarze, A.; Müller-Schwarze, C. (1994). "Red maple (Acer rubrum) inhibits feeding by beaver (Castor canadensis)". Journal of Chemical Ecology. 20 (8): 2021–2034. doi:10.1007/BF02066240. ISSN 0098-0331. PMID 24242726. S2CID 13529462.
  68. ^ Thurber, J. M.; Peterson, R. O. (1993). "Effects of Population Density and Pack Size on the Foraging Ecology of Gray Wolves". Journal of Mammalogy. 74 (4): 879. doi:10.2307/1382426. JSTOR 1382426. S2CID 52063038.
  69. ^ "The American Bear Association Home Page (Web Pages2/index)". The American Bear Association. Archived from the original on July 26, 2013.
  70. ^ "Adirondack Black Bears". Environmental Information Series.
  71. ^ Smith, D. W.; Trauba, D. R.; Anderson, R. K.; Peterson, R. O. (1994). "Black bear predation on beavers on an island in Lake Superior". American Midland Naturalist. 132 (2): 248–255. doi:10.2307/2426580. JSTOR 2426580.
  72. ^ Engelhart, A; Müller-Schwarze, D (1995). "Responses of beaver (Castor canadensis Kuhl) to predator chemicals". Journal of Chemical Ecology. 21 (9): 1349–64. doi:10.1007/BF02027567. PMID 24234632. S2CID 9743116.
  73. ^ "Beaver". Study of Northern Virginia Ecology, Fairfax County Public School. Archived from the original on January 5, 2013. Retrieved January 3, 2013.
  74. ^ Müller-Schwarze, Dietland & Sun, Lixing (2003). The Beaver: Natural History of a Wetlands Engineer. Cornell University Press. pp. 113–114. ISBN 978-0-8014-4098-4.
  75. ^ "Beaver Biology". Beaver Solutions. Archived from the original on April 14, 2010. Retrieved November 22, 2013.
  76. ^ Müller-Schwarze, Dietland & Sun, Lixing (2003). The Beaver: Natural History of a Wetlands Engineer. Cornell University Press. p. 80. ISBN 978-0-8014-4098-4.
  77. ^ "N. America's Earliest Beaver Found Near Dayville – Discovered Teeth "A Dam Important Find,' Scientists Say". KVTZ. September 19, 2011. Archived from the original on September 25, 2011. Retrieved September 20, 2011.
  78. ^ "Integrated Taxonomic Information System (ITIS) - ScienceBase-Catalog". www.sciencebase.gov. Retrieved December 2, 2020.
  79. ^ Baker, B. W. and Hill, E. P. (2003). "Beaver (Castor canadensis)". G. A. Feldhamer, B. C. Thompson, and J. A. Chapman, editors. Wild Mammals of North America: Biology, Management, and Conservation. Second Edition. The Johns Hopkins University Press, Baltimore, Maryland, USA, pp. 288–310.
  80. ^ Kieffer, Michael Meadows in Mist Archived September 29, 2007, at the Wayback Machine Bull Run Mountains Conservancy, Inc. Retrieved August 4, 2007.
  81. ^ a b Kitchener, Andrew (2001). Beavers. p. 144. ISBN 978-1-873580-55-4.
  82. ^ Moloney, F. X. (1967). The Fur Trade in New England, 1620–1676. Hamden, Connecticut: Archon Books. p. 150.
  83. ^ Hays, W. J. (September 1871). "Notes on the range of some of the animals in America at the time of arrival of the whitemen". The American Naturalist. 5 (7): 25–30. doi:10.1086/270797. JSTOR 2447602.
  84. ^ Coles, J. M.; Orme, B. J. (1983). "Home sapiens or Castor fiber?". Antiquity. 57 (220): 95–102. doi:10.1017/S0003598X00055265.
  85. ^ Seton-Thompson, cited in Sun, Lixing; Müller-Schwarze, Dietland (2003). The Beaver: Natural History of a Wetlands Engineer. Ithaca, NY: Cornell University Press. pp. 97–98. ISBN 978-0-8014-4098-4.; but note that to arrive at this figure he assumed a population density throughout the range equivalent to that in Algonquin Park
  86. ^ Outwater, Alice (1997). Water:A Natural History. New York, NY: Basic Books. p. 89. ISBN 978-0-465-03780-3.
  87. ^ "Trees in parks & ravines - beavers". 311 Toronto. City of Toronto. 2018. Retrieved July 29, 2019.
  88. ^ Parks, Mike (March 1, 2012). "South Charlotte Weekly: Beavers damaging Park Road Park; must go". Thecharlotteweekly.com.
  89. ^ "Beavers: Wetlands & Wildlife: Solutions to Beaver/Human Conflicts". Beaversww.org. Archived from the original on February 20, 2008. Retrieved March 16, 2013.
  90. ^ Agar, Charles (March 24, 2008). "Beaver Deceiver expert coming to Pitkin County". The Aspen Times. Aspen, Colorado. Archived from the original on January 18, 2010. Retrieved November 22, 2009.
  91. ^ Wright, J.P.; Jones, C.G.; Flecker, A.S. (2002). "An ecosystem engineer, the beaver, increases species richness at the landscape scale". Oecologia. 132 (1): 96–101. Bibcode:2002Oecol.132...96W. doi:10.1007/s00442-002-0929-1. PMID 28547281. S2CID 5940275.
  92. ^ Rosell F; Bozser O; Collen P; Parker H (2005). "Ecological impact of beavers Castor fiber and Castor canadensis and their ability to modify ecosystems" (PDF). Mammal Review. 35 (3–4): 248–276. doi:10.1111/j.1365-2907.2005.00067.x. hdl:11250/2438080. Retrieved March 1, 2010.
  93. ^ Polly P. Gibson and Julian D. Olden (2014). "Ecology, management, and conservation implications of North American beaver (Castor canadensis) in dryland streams". Aquatic Conservation: Marine and Freshwater Ecosystems. 24 (3): 391–409. doi:10.1002/aqc.2432. S2CID 7062322.CS1 maint: uses authors parameter (link)
  94. ^ a b Anderson, Christopher B.; Pastur, Guillermo Martinez; Lencinas, Maria Vanessa; Wallem, Petra K.; Moorman, Michelle C. & Rosemond, Amy D. (2009). "Do introduced North American beavers Castor canadensis engineer differently in southern South America? An overview with implications for restoration" (PDF). Mammalian Review. 39: 33–52. doi:10.1111/j.1365-2907.2008.00136.x. Retrieved March 17, 2012.
  95. ^ Vila, I.; Fuentes, L. S. & Saavedra, M. (1999). "Ictiofauna en los sistema límnicos de la Isla Grande, Tierra del Fuego, Chile" (PDF). Revista Chilena de Historia Natural: 273–284.
  96. ^ a b Moorman, Michelle C.; Eggleston, David B.; Anderson, Christopher B.; Mansilla, Andres & Szejner, Paul (2009). "Implications of Beaver Castor canadensis and Trout Introductions on Native Fish in the Cape Horn Biosphere Reserve, Chile". Transactions of the American Fisheries Society. 138 (2): 306–313. doi:10.1577/T08-081.1. S2CID 55446746.
  97. ^ Wallem, P. K.; Jones, C. G.; Marquet, P. A. & Jaksic, F. M. (2007). "Identificación de los mecanismo subyacentes a la invasión de Castor canadensis (Kuhl 1820, Rodentia) en el archipiélago de Tierra del Fuego, Chile". Revista Chilena de Historia Natural: 309–325.
  98. ^ "Argentina eager to rid island of beavers". CNN. Retrieved May 20, 2010.
  99. ^ a b Frosch, Christiane; Kraus, Robert H. S.; Angst, Christof; Allgöwer, Rainer; Michaux, Johan; Teubner, Jana; Nowak, Carsten (May 14, 2014). "The Genetic Legacy of Multiple Beaver Reintroductions in Central Europe". PLOS ONE. 9 (5): e97619. doi:10.1371/journal.pone.0097619. ISSN 1932-6203. PMC 4020922. PMID 24827835.
  100. ^ a b Parker, Howard; Nummi, Petri; Hartman, Göran; Rosell, Frank (2012). "Invasive North American beaver Castor canadensis in Eurasia: a review of potential consequences and a strategy for eradication". Wildlife Biology. 18 (4): 354–365. doi:10.2981/12-007. ISSN 0909-6396. S2CID 54928567.
  101. ^ Hartmann, Goran (1999). Beaver Protection, Management, and Utilization in Europe and North America. New York: Kluwer. pp. 1–14.
  102. ^ a b Nummi, Petri. "NOBANIS – Invasive Alien Species Fact Sheet – Castor canadensis" (PDF). Online Database of the European Network on Invasive Alien Species. NOBANIS. Retrieved October 2, 2014.
  103. ^ Poirier, Nelson (November 27, 2010). "Our symbolic beaver overcomes challenges of past". Moncton, New Brunswick: Times & Transcript. Archived from the original on August 21, 2011. Retrieved November 18, 2010.
  104. ^ a b The Beaver Heritage Canada
  105. ^ International, Radio Canada (April 23, 2015). "History: Apr. 23, 1851, Canada issues first stamp". RCI | English. Retrieved May 29, 2017.
  106. ^ The HBC Coat of Arms, Hbc Heritage
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North American beaver: Brief Summary

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The North American beaver (Castor canadensis) is one of two extant beaver species, along with the Eurasian beaver (Castor fiber). It is native to North America and introduced in South America (Patagonia) and Europe (primarily Finland and Karelia). In the United States and Canada, the species is often referred to simply as "beaver", though this causes some confusion because another distantly related rodent, Aplodontia rufa, is often called the "mountain beaver". Other vernacular names, including American beaver and Canadian beaver, distinguish this species from the other extant beaver species, Castor fiber, which is native to Eurasia. The North American beaver is one of the official national wildlife of Canada symbols and is the official state mammal of Oregon and New York.

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