American Beaver
Encyclopedia
The North American Beaver (Castor canadensis) is the only species
of beaver
in the Americas
, native to North America
and introduced to South America
. In the United States
and Canada
, where no other species of beaver occurs, it is usually simply referred to as "beaver". Its other vernacular names, including American beaver and Canadian beaver, distinguish this species from the one other extant beaver, Castor fiber, native to Eurasia
. ("Canadian beaver" also refers to the subspecies Castor canadensis canadensis.)
and the third largest rodent in the world, after the South America
n capybara
and the Eurasian beaver. Adults usually weigh 15 kilogram, with 20 kilogram a typical mass, and measure around 1 m (3.3 ft) in total body length. Very old individuals can weigh as much as 45 kilogram.
Like the capybara, the beaver is semi-aquatic. The beaver has many traits suited to this lifestyle. It has a large flat paddle-shaped tail and large, webbed hind feet reminiscent of a human diver's swimfin
s. The unwebbed front paws are smaller, with claws. The eyes are covered by a nictitating membrane
which allows the beaver to see underwater. The nostrils and ears are sealed while submerged. A thick layer of fat under its skin insulates the beaver from its cold water 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 colours but usually is dark brown. Scent gland
s near the genitals secrete an oily substance known as castoreum
, which the beaver uses to waterproof its fur.
Before their near extirpation
by trapping in North America, beaver were practically ubiquitous and lived from the arctic tundra
to the deserts of northern Mexico
, and from the Atlantic
to the Pacific Ocean
s. Physician naturalist Edgar Alexander Mearns
' 1907 report of beaver on the Sonora River
may be the southernmost extent of the range of this North American aquatic mammal. However, beaver have also been reported both historically and contemporaneously in Mexico on the Colorado River
, Bavispe River
and San Bernardino River
. Explorer David Thompson
, after crossing much of North America in 1784, stated that "this Continent...from the Atlantic to the Pacific Ocean, may be said to have been in the possession of two distinct races of Beings, Man and the Beaver."
Beavers are mainly active at night. They are excellent swimmers but are more vulnerable on land and tend to remain in the water as much as possible. They are able to remain submerged for up to 15 minutes. 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, and mud in lake
s, stream
s, and tidal
river delta
s. These lodges may be surrounded by water, or touching land, including burrows dug into river banks. They are well known for building dam
s across streams and constructing their lodge in the artificial pond which forms. 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.
The dam
is constructed using logs from trees the beavers cut down, as well as rocks, grass and mud. The inner bark, twigs, shoots and leaves of such trees are also an important part of the beaver's diet. The trees are cut down using their strong incisor
teeth. Their front paws are used for digging and carrying and placing materials. Some researchers have shown that 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 don't repair breaches in the dam made by otters, and sometimes breach the dam themselves and lower the water level in the pond in order 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. .
Beavers are most famous, and infamous, 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 questioned when a recording of running water was played in a field near a beaver pond. Despite the fact that it was on dry land, the beaver covered the tape player with branches and mud. The largest beaver dam is 2790 ft (850.4 m) in length—more than half a mile long—and was discovered via satellite imagery in 2007. It is located on the southern edge of Wood Buffalo National Park
in northern Alberta
and is twice the width of the Hoover Dam
which spans 1244 ft (379.2 m).
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. They prefer aspen and poplar, but will also take birch, maple, willow, alder, black cherry, red oak, beech, ash, hornbeam and occasionally pine and spruce. They will also eat cattails, water lilies
and other aquatic vegetation, especially in the early spring (and contrary to widespread belief, they do not eat fish). In areas where their pond freezes over, beavers collect food in late fall in the form of tree branches, storing them underwater (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.
Beavers usually mate for life. The young beaver "kits" typically remain with their parents for up to two years.
Common natural predators include gray wolves
, coyote
s, and mountain lions. Less significant predators include bear
s, which can dig into a lodge, wolverine
s, fox
, Canadian lynx, bobcat
s, and alligators. Despite repeated claims there is no evidence that river otters
are predators of beavers.
. The oldest fossil record of beaver in North America are of two beaver teeth in Dayville, Oregon
and are 7 million years old.
There are 25 subspecies of beaver in North America, but different subspecies have been reintroduced to areas with previously geographically isolated subspecies, following population decline or extirpation of the indigenous subspecies. This has led to very substantial mixing of the subspecies gene pools, and some subspecies may have disappeared entirely.
The most widespread subspecies are C. c. acadicus (New England beaver), C. c. canadensis (Canadian beaver), C. c. carolinensis (Carolina beaver), and C. c. missouriensis (Missouri River beaver). The Canadian beaver originally inhabited almost all of the forested area of Canada, 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.
(Castor fiber), there are several important differences between the two species. North American beavers tend to be smaller, with smaller, more rounded heads, shorter, wider muzzles, thicker, longer and darker underfur, wider, more oval-shaped tails and have 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 cousins, 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 colour is also different. Overall, 50% of North American beavers have pale brown fur, 25% are reddish brown, one fifth are brown and 6% are blackish, while in European beavers 66% have pale brown or beige fur, 20% have reddish brown, nearly 8% are brown and only 4% have blackish coats.
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.
s. 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. From 1630 to 1640, approximately 80,000 beaver were taken annually from the Hudson River
and western New York. As eastern beaver populations were depleted, French and American trappers pushed west. In fact, 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
, there was an earlier 19th century California Fur Rush
which drove the earliest American settlement in that State. During the approximately 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; however this is still a fraction of the originally estimated 100 to 200 million North American beaver before the days of the fur trade
.
These animals are considered pest
s in some parts of their range because their dams can cause flooding in nearby areas. Because they are persistent in repairing any damage to the dam, they were historically relocated or exterminated. However, non-lethal methods of containing beaver-related flooding have been developed. One such flow device
has been utilized by both the Canadian and U.S. governments, called "Beaver Deceivers," or levelers, invented and pioneered by wildlife biologist, Skip Lisle.
The beaver is a keystone species
, increasing biodiversity in its territory through creation of beaver ponds and wetlands. As wetlands are formed and riparian habitats enlarged, aquatic plants colonize newly available watery habitat. Insect, invertebrate, fish, mammal, and bird diversity are also expanded.
, Canada found that the mammals were associated with a 9-fold increase in open water area. Beaver returned to the area in 1954 after a long absence since their extirpation by the fur trade in the nineteenth century. Even during drought years, where beaver were present, there was 60 per cent more open water than those same areas during previous drought periods when beaver were absent. The authors concluded that beaver have a dramatic influence on the creation and maintenance of wetlands even during extreme drought.
From streams from the Maryland
coastal plain in the east to Lake Tahoe
in the west, beaver ponds have been shown to remove sediment and pollutants including total suspended solids, total nitrogen, phosphates, carbon and silicates, improving stream water quality. In addition, fecal coliform and streptococci bacteria excreted into streams by grazing cattle are reduced by beaver ponds, where slowing currents lead to settling of the bacteria in bottom sediments.
The term "beaver fever" is a misnomer coined by the American press in the 1970s, following findings that the parasite Giardia lamblia
, which causes Giardiasis
, is carried by beavers. However, further research has shown that the many animals and birds carry this parasite, and the major source of water contamination is by other humans. Recent concerns point to domestic animals as a significant vector of giardia with young calves in dairy herds testing as high as 100% positive for giardia. In addition, fecal coliform and streptococci bacteria excreted into streams by grazing cattle have been shown to be reduced by beaver ponds, where the bacteria are trapped in bottom sediments. In fact, New Zealand
has giardia outbreaks but no beaver, whereas Norway
has plenty of beaver but had no giardia outbreaks until recently (in a southern part of Norway densely populated by humans but no beaver).
s (Cygnus buccinator) and Canada geese
(Branta canadensis) often depend on beaver lodges as nesting sites. Canada's small trumpeter swan population was observed not to nest on large lakes, preferring instead to nest on the smaller lakes and ponds associated with beaver activity.
Beaver may benefit the birds frequenting their ponds in several additional ways. Removal of some pondside trees by beavers would increase the density and height of the grass–forb–shrub layer, which enhances waterfowl nesting cover adjacent to ponds. Both forest gaps where trees had been felled by beaver and a "gradual edge" described as a complex transition from pond to forest with intermixed grasses, forbs, saplings, and shrubs are strongly associated with greater migratory bird species richness and abundance. Coppicing
of waterside willows and cottonwoods by beavers leads to dense shoot production which provides important cover for birds and the insects they feed on.
As trees are drowned by rising beaver impoundments they become ideal nesting sites for woodpeckers, who carve cavities that attract many other bird species including flycatchers
(Empidonax spp.), tree swallow
s (Tachycineta bicolor), tits (Paridae spp.), wood duck
s (Aix sponsa), goldeneye
s (Bucephala spp.), mergansers (Mergus spp.), owl
s (Titonidae, Strigidae) and American kestrel
s (Falco sparverius). Piscivores, including heron
s (Ardea spp.), grebe
s (Podicipedidae), cormorant
s (Phalacrocorax ssp.), American bittern
s (Botaurus lentiginosa), great egret
(Ardea alba), snowy egret
(Egretta thula), mergansers and belted kingfisher
s (Megaceryle alcyon), utilize beaver ponds for fishing. Hooded merganser
s (Lophodytes cucullatus), green heron
(Butorides virescens), great blue heron
(Ardea herodias) and belted kingfisher occurred more frequently in New York wetlands where beaver were active than at sites with no beaver activity.
basin in Washington state, found that extensive loss of beaver ponds resulted in an 89% reduction in coho salmon
(Oncorhynchus kisutch) smolt summer production and an almost equally detrimental 86% reduction in critical winter habitat carrying capacity
. Swales and Leving had previously shown on the Coldwater River
in British Columbia
that off-channel beaver ponds were preferentially populated by coho salmon over other salmonids and provided overwintering protection, protection from high summer snowmelt flows and summer coho rearing habitat. The presence of beaver dams has also been shown to either increase the number of fish, their size, or both, in a study of brook trout
(Salvelinus fontinalis), rainbow trout
(Oncorhynchus mykiss) and brown trout
(Salmo trutta) in Sagehen Creek, which flows into the Little Truckee River
at an altitude of 5,800 feet in the northern Sierra Nevada. These findings are consistent with a study of small streams in Sweden
, that found that brown trout were larger in beaver ponds compared with those in riffle
sections, and that beaver ponds provide habitat for larger trout in small streams during periods of drought. Similarly, brook trout, coho salmon and sockeye salmon
(Oncorhynchus nerka) were significantly larger in beaver ponds than those in un-impounded stream sections in Colorado
and Alaska
. Contrary to popular myth, most beaver dams do not pose barriers to trout and salmon migration, although they may be restricted seasonally during periods of low stream flows. Rainbow, brown and brook trout have been shown to cross as many as 14 consecutive beaver dams. Both adults and juveniles of coho salmon, steelhead trout, sea run cutthroat
(Oncorhyncus clarki clarki), Dolly Varden trout
(Salvelinus malma malma), and sockeye salmon are able to cross beaver dams. In southeast Alaska, coho jumped dams as high as 2 meters, were found above all beaver dams and had their highest densities in streams with beaver. In Oregon coastal streams, beaver dams are ephemeral and almost all wash out in high winter flows only to be re-built every summer. Migration of adult Atlantic salmon
(Salmo salar) may be limited by beaver dams but the presence of juveniles upstream from the dams suggests that the dams are penetrated by parr. Downstream migration of Atlantic salmon smolts was similarly unaffected by beaver dams, even in periods of low flows. Two year old Atlantic salmon parr in beaver ponds in eastern Canada showed faster summer growth in length and mass and were in better condition than parr upstream or downstream from the pond. The importance of winter habitat to salmonids afforded by beaver ponds may be especially important (and underappreciated) in streams without deep pools or where ice cover makes contact with the bottom of shallow streams. Enos Mills wrote in 1913, "One dry winter the stream...ran low and froze to the bottom, and the only trout in it that survived were those in the deep holes of beaver ponds." Cutthroat trout
(Oncorhynchus clarki) and bull trout
(Salvelinus confluentus) were noted to overwinter in Montana beaver ponds, brook trout congregated in winter in New Brunswick and Wyoming beaver ponds, and coho salmon in Oregon beaver ponds. In 2011 a meta-analysis of studies of beaver impacts on salmonids found that beaver were a net benefit to salmon and trout populations primarily by improving habitat (building ponds) both for rearing and overwintering and that this conclusion was based over half the time on scientific data. In contrast, the most often cited negative impact of beavers on fishes were barriers to migration although that conclusion was based on scientific data only 29% of the time. They also found that when beaver dams do present barriers that these are generally short-lived, as the dams are overtopped or blown out by storm surges.
Efforts to restore salmonid habitat in the western United States have focused primarily on establishing large woody debris
in streams to slow flows and create pools for young salmonids. However research in Washington state found that the average summer smolt production per beaver dam ranges from 527 to 1,174 fish, whereas the summer smolt production from a pool formed by instream large woody debris is about 6–15 individuals, suggesting that re-establishment of beaver populations would be 80 times more effective.
Recently, beaver have been discovered living in brackish water in estuarine tidal marshes, where Chinook salmon
(Oncorhynchus tshawytscha) densities were five times higher in beaver ponds than in neighboring areas.
in the Sierra Nevada mountains, however Willow
(Salix spp.) responded by re-growing vigorously in most reaches. He further speculated that without control of beaver populations that aspen and cottonwood could go extinct on the Truckee River. However, not only have aspen and cottonwood survived ongoing beaver colonization but a recent study of ten Sierra Nevada streams in the Lake Tahoe
basin utilizing aerial multispectral videography has shown that deciduous, thick herbaceous, and thin herbaceous vegetation are more highly concentrated near beaver dams, whereas coniferous trees are decreased. These findings are consistent with those of Pollock, who reported that in Bridge Creek, a stream in semi-arid eastern Oregon, the width of riparian vegetation on stream banks was increased several-fold as beaver dams watered previously dry terraces adjacent to the stream. In a second study of riparian vegetation based on observations of Bridge Creek over a 17 year time period, although portions of the study reach were periodically abandoned by beaver following heavy utilization of streamside vegetation, within a few years dense stands of woody plants of greater diversity occupied a larger portion of the floodplain. Although black cottonwood and thinleaf alder did not generally re-sprout after beaver cutting, they frequently grew from seeds landing on freshly exposed alluvial deposits secondary to beaver activity. Therefore, beaver appear to increase riparian vegetation given enough years to aggrade sediments and pond heights sufficiently to create widened, well-watered riparian zones, especially in areas of low summer rainfall.
The surface of beaver ponds are typically at or near bank-full, so even small increases in stream flows cause the pond to overflow its banks. Thus, high stream flows spread water and nutrients to beyond the stream banks to wide riparian zones when beaver dams are present.
in projects to stop soil erosion by streams in Oregon, Washington, Wyoming, and Utah. At the time it was estimated that each beaver, whose initial cost was about $5, completed work worth $300.
In a pilot study in Washington state, the Lands Council is reintroducing beavers to evaluate their projections that if 10,000 miles of suitable habitat were repopulated then 650 trillion gallons of spring runoff would be held back for release in the arid fall season. This project was developed in response to a 2003 Washington Department of Ecology
proposal to spend as much as ten billion dollars on construction of several dams on Columbia River
tributaries to retain storm season runoff. The State of Utah
published a Beaver Management Plan which includes re-establishing beavers in ten streams per year for the purpose of watershed restoration each year from 2010 through 2020.
in 2007, making its home along the Bronx River
, having spent time living at the Bronx Zoo
as well as the Botanical Gardens. Beavers have not lived in New York City since the early 19th century when trappers extirpated them completely from the state. The return of "Jose", named after Representative Jose Serrano from the Bronx, has been seen as evidence that efforts to restore the river have been successful. In the summer of 2010 a second beaver joined Jose, doubling the beaver population in New York City. Beaver were once important to the city's economy and a pair of beavers appears on the city's official seal and flag.
In Chicago
, several beavers have returned and made a home near the Lincoln Park
's North Pond. The "Lincoln Park Beaver" has not been as well received by the Chicago Park District
and the Lincoln Park
Conservancy, which was concerned over damage to trees in the area. In March 2009, they hired an exterminator to remove a beaver family using live traps, and accidentally killed the mother when she got caught in a snare and drowned. Relocation costs $4,000-$4,500 per animal. Scott Garrow, District Wildlife Biologist with the Illinois Department of Natural Resources
, opined that relocating the beavers may be "a waste of time", as there are records of beaver recolonizing North Pond in Lincoln Park in 1994, 2003, 2004, 2008 and 2009. As of fall 2009 a new beaver lodge has appeared on North Pond's northwest bank.
Outside San Francisco, in downtown Martinez, California
, a male and female beaver arrived in Alhambra Creek
in 2006. The Martinez beavers built a dam 30 feet wide and at one time 6 feet high, and chewed through half the willows and other creekside landscaping the city planted as part of its $9.7 million 1999 flood-improvement project. When the City Council wanted to remove the beavers because of fears of flooding, local residents organized to protect them, forming an organization called "Worth a Dam". Resolution included installation of a flow device
through the beaver dam
so that the pond's water level could not become excessive. Now protected, the beaver have transformed Alhambra Creek from a trickle into multiple dams and beaver ponds, which in turn, lead to the return of steelhead trout and river otter in 2008, and mink
in 2009. The Martinez beavers probably originated from the Sacramento-San Joaquin River Delta which once held the largest concentration of beaver in North America.
In 1999, Washington, D.C.
's annual Cherry Blossom Festival
was plagued by a family of beavers who lived in the Tidal Basin
. The offenders were caught and removed, but not before damaging 14 cherry trees, including some of the largest and oldest trees.
In the 1940s, beavers were brought to the island of Tierra Del Fuego
in southern Chile
and Argentina
, for commercial fur production. However, the project failed and the beavers, a few pairs, were released into the wild. Having no natural predators in their new environment, they quickly spread throughout the island, and to other islands in the region, reaching a number of 100,000 individuals within just 50 years. They are now considered a serious invasive species
in the region, due to their massive destruction of forest trees, and efforts are being made for their eradication. The drastically different ecosystem has led to substantial environmental damage, as the ponds created by the beavers have no ecological purpose (wetlands do not form there as they do in the beavers' native territory) and there are no native, large predators. They have also been found to cross saltwater to islands northward; a possible encroachment on the mainland has naturalists highly concerned.
In contrast, areas with introduced beaver were associated with increased populations of native puye
fish (Galaxias maculatus), whereas the exotic brook trout
(Salvelinus fontinalis) and rainbow trout
(Oncorhynchus mykiss) had negative impacts on native stream fishes in the Cape Horn Biosphere Reserve
, Chile
.
, 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.
Despite their name, the fried pastries found in parts of Canada called beaver tails
contain no beaver.
and was on the first Canadian postage stamp, the Three Penny Beaver. It is also the state animal of Oregon
and New York, 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
. The beaver also appears in the coats of arms
of the Hudson's Bay Company
, University of Toronto
, Wilfrid Laurier University
, and the London School of Economics
.
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.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of beaver
Beaver
The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...
in the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
, native to North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and introduced to South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, where no other species of beaver occurs, it is usually simply referred to as "beaver". Its other vernacular names, including American beaver and Canadian beaver, distinguish this species from the one other extant beaver, Castor fiber, native to Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
. ("Canadian beaver" also refers to the subspecies Castor canadensis canadensis.)
Description
This beaver is the largest rodent in North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
and the third largest rodent in the world, after the South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n capybara
Capybara
The capybara , also known as capivara in Portuguese, and capibara, chigüire in Venezuela, Colombia, and Ecuador ronsoco in Peru, chigüiro, and carpincho in Spanish, is the largest living rodent in the world. Its closest relatives are agouti, chinchillas, coyphillas, and guinea pigs...
and the Eurasian beaver. Adults usually weigh 15 kilogram, with 20 kilogram a typical mass, and measure around 1 m (3.3 ft) in total body length. Very old individuals can weigh as much as 45 kilogram.
Like the capybara, the beaver is semi-aquatic. The beaver has many traits suited to this lifestyle. It has a large flat paddle-shaped tail and large, webbed hind feet reminiscent of a human diver's swimfin
Swimfin
Swimfins, swim fins, fins or flippers are worn on the foot or leg and made from finlike rubber or plastic, to aid movement through the water in water sports activities such as swimming, bodyboarding, bodysurfing, kneeboarding, riverboarding, and various types of underwater diving.Scuba divers use...
s. The unwebbed front paws are smaller, with claws. The eyes are covered by a nictitating membrane
Nictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...
which allows the beaver to see underwater. The nostrils and ears are sealed while submerged. A thick layer of fat under its skin insulates the beaver from its cold water environment.
The beaver's fur
Fur
Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to animal...
consists of long, coarse outer hairs and short, fine inner hairs (see Double coat). The fur has a range of colours but usually is dark brown. Scent gland
Scent gland
Scent glands are found in the genital area of most mammals and in various other parts of the body, such as the underarms of humans and the preorbital glands of deer and muskox. They produce a semi-viscous fluid which contains pheromones. These odor-messengers indicate information such as status,...
s near the genitals secrete an oily substance known as castoreum
Castoreum
Castoreum is the exudate from the castor sacs of the mature North American Beaver Castor canadensis and the European Beaver Castor fiber. Within the zoological realm, castoreum is the yellowish secretion of the castor sac in combination with the beaver's urine, used during scent marking of territory...
, which the beaver uses to waterproof its fur.
Before their near extirpation
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...
by trapping in North America, beaver were practically ubiquitous and lived from the arctic tundra
Tundra
In physical geography, tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sami word tūndâr "uplands," "treeless mountain tract." There are three types of tundra: Arctic tundra, alpine...
to the deserts of northern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, and from the Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
to the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
s. Physician naturalist Edgar Alexander Mearns
Edgar Alexander Mearns
Edgar Alexander Mearns was a notable American ornithologist and field naturalist....
' 1907 report of beaver on the Sonora River
Sonora River
Río Sonora is a 402-kilometer-long river of Mexico. It lies on the Pacific slope of the Mexican state of Sonora and it runs into the Gulf of California.-Watershed:...
may be the southernmost extent of the range of this North American aquatic mammal. However, beaver have also been reported both historically and contemporaneously in Mexico on the Colorado River
Colorado River
The Colorado River , is a river in the Southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states...
, Bavispe River
Bavispe River
The Rio Bavispe or Bavispe River is a river in Mexico which flows briefly north then mainly south by southwest until it joins with the Aros River to become the Yaqui River, eventually joining the Gulf of California.-History:...
and San Bernardino River
San Bernardino River
The Rio San Bernardino, or San Bernardino River, begins in extreme southeastern Cochise County, Arizona and is a tributary of the Bavispe River, in Sonora, Mexico. It is named after one of Southern California's largest cities, San Bernardino.-Watershed:...
. Explorer David Thompson
David Thompson (explorer)
David Thompson was an English-Canadian fur trader, surveyor, and map-maker, known to some native peoples as "Koo-Koo-Sint" or "the Stargazer"...
, after crossing much of North America in 1784, stated that "this Continent...from the Atlantic to the Pacific Ocean, may be said to have been in the possession of two distinct races of Beings, Man and the Beaver."
Behaviour
They construct their homes, or "lodges," out of sticks, twigs, and mud in lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
s, stream
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
s, and tidal
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
river delta
River delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
s. These lodges may be surrounded by water, or touching land, including burrows dug into river banks. They are well known for building dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
s across streams and constructing their lodge in the artificial pond which forms. 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.
The dam
Beaver dam
Beaver dams are dams built by beavers as protection against predators such as coyotes, wolves, and bears, and to provide easy access to food during winter. Beavers work at night and are prolific builders, carrying mud and stones with their fore-paws and timber between their teeth...
is constructed using logs from trees the beavers cut down, as well as rocks, grass and mud. The inner bark, twigs, shoots and leaves of such trees are also an important part of the beaver's diet. The trees are cut down using their strong incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
teeth. Their front paws are used for digging and carrying and placing materials. Some researchers have shown that 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
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
, fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, and other aquatic animals. Their dams help reduce soil erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
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 don't repair breaches in the dam made by otters, and sometimes breach the dam themselves and lower the water level in the pond in order 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. .
Beavers are most famous, and infamous, 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 questioned when a recording of running water was played in a field near a beaver pond. Despite the fact that it was on dry land, the beaver covered the tape player with branches and mud. The largest beaver dam is 2790 ft (850.4 m) in length—more than half a mile long—and was discovered via satellite imagery in 2007. It is located on the southern edge of Wood Buffalo National Park
Wood Buffalo National Park
Wood Buffalo National Park, located in northeastern Alberta and southern Northwest Territories, is the largest national park in Canada at . The park was established in 1922 to protect the world's largest herd of free roaming Wood Bison, currently estimated at more than 5,000...
in northern Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
and is twice the width of the Hoover Dam
Hoover Dam
Hoover Dam, once known as Boulder Dam, is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the US states of Arizona and Nevada. It was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President...
which spans 1244 ft (379.2 m).
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. They prefer aspen and poplar, but will also take birch, maple, willow, alder, black cherry, red oak, beech, ash, hornbeam and occasionally pine and spruce. They will also eat cattails, water lilies
Nymphaeaceae
Nymphaeaceae is a family of flowering plants. Members of this family are commonly called water lilies and live in freshwater areas in temperate and tropical climates around the world. The family contains eight genera. There are about 70 species of water lilies around the world. The genus...
and other aquatic vegetation, especially in the early spring (and contrary to widespread belief, they do not eat fish). In areas where their pond freezes over, beavers collect food in late fall in the form of tree branches, storing them underwater (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.
Beavers usually mate for life. The young beaver "kits" typically remain with their parents for up to two years.
Common natural predators include gray wolves
Gray Wolf
The gray wolf , also known as the wolf, is the largest extant wild member of the Canidae family...
, coyote
Coyote
The coyote , also known as the American jackal or the prairie wolf, is a species of canine found throughout North and Central America, ranging from Panama in the south, north through Mexico, the United States and Canada...
s, and mountain lions. Less significant predators include bear
Bear
Bears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern...
s, which can dig into a lodge, wolverine
Wolverine
The wolverine, pronounced , Gulo gulo , also referred to as glutton, carcajou, skunk bear, or quickhatch, is the largest land-dwelling species of the family Mustelidae . It is a stocky and muscular carnivore, more closely resembling a small bear than other mustelids...
s, fox
Fox
Fox is a common name for many species of omnivorous mammals belonging to the Canidae family. Foxes are small to medium-sized canids , characterized by possessing a long narrow snout, and a bushy tail .Members of about 37 species are referred to as foxes, of which only 12 species actually belong to...
, Canadian lynx, bobcat
Bobcat
The bobcat is a North American mammal of the cat family Felidae, appearing during the Irvingtonian stage of around 1.8 million years ago . With twelve recognized subspecies, it ranges from southern Canada to northern Mexico, including most of the continental United States...
s, and alligators. Despite repeated claims there is no evidence that river otters
Northern River Otter
The North American river otter , also known as the northern river otter or the common otter, is a semiaquatic mammal endemic to the North American continent, found in and along its waterways and coasts. An adult river otter can weigh between 5 and 14 kg...
are predators of beavers.
Reproduction
North American beaver 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 average three kits per litter with a range of two to six kits. Most beaver do not reproduce until they are three years of age, but about 20% of two year old females reproduce.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 StraitBering Strait
The Bering Strait , known to natives as Imakpik, is a sea strait between Cape Dezhnev, Chukotka Autonomous Okrug, Russia, the easternmost point of the Asian continent and Cape Prince of Wales, Alaska, USA, the westernmost point of the North American continent, with latitude of about 65°40'N,...
. The oldest fossil record of beaver in North America are of two beaver teeth in Dayville, Oregon
Dayville, Oregon
Dayville is a city in Grant County, Oregon, United States. It was incorporated in 1913. The population was 138 at the 2000 census.-Geography:According to the United States Census Bureau, the city has a total area of , all land....
and are 7 million years old.
There are 25 subspecies of beaver in North America, but different subspecies have been reintroduced to areas with previously geographically isolated subspecies, following population decline or extirpation of the indigenous subspecies. This has led to very substantial mixing of the subspecies gene pools, and some subspecies may have disappeared entirely.
The most widespread subspecies are C. c. acadicus (New England beaver), C. c. canadensis (Canadian beaver), C. c. carolinensis (Carolina beaver), and C. c. missouriensis (Missouri River beaver). The Canadian beaver originally inhabited almost all of the forested area of Canada, 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
Missouri River
The Missouri River flows through the central United States, and is a tributary of the Mississippi River. It is the longest river in North America and drains the third largest area, though only the thirteenth largest by discharge. The Missouri's watershed encompasses most of the American Great...
and its tributaries, and C. c. acadicus is found throughout the New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
area in the northeastern United States.
Differences from European beaver
Although superficially similar to the European beaverEuropean Beaver
The Eurasian beaver or European beaver is a species of beaver, which was once widespread in Eurasia, where it was hunted to near extinction both for fur and for castoreum, a secretion of its scent gland believed to have medicinal properties...
(Castor fiber), there are several important differences between the two species. North American beavers tend to be smaller, with smaller, more rounded heads, shorter, wider muzzles, thicker, longer and darker underfur, wider, more oval-shaped tails and have 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 cousins, 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 colour is also different. Overall, 50% of North American beavers have pale brown fur, 25% are reddish brown, one fifth are brown and 6% are blackish, while in European beavers 66% have pale brown or beige fur, 20% have reddish brown, nearly 8% are brown and only 4% have blackish coats.
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.
Ecology
The beaver was trapped out and almost extirpated in North America as its fur and castoreum were highly sought after. The beaver furs were used to make clothing and beaver hatBeaver hat
A beaver hat is a hat made from felted beaver fur. They were fashionable across much of Europe during the period 1550-1850 because the soft yet resilient material could be easily combed to make a variety of hat shapes...
s. 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
Connecticut
Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...
and Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
between 1620 and 1630. From 1630 to 1640, approximately 80,000 beaver were taken annually from the Hudson River
Hudson River
The Hudson is a river that flows from north to south through eastern New York. The highest official source is at Lake Tear of the Clouds, on the slopes of Mount Marcy in the Adirondack Mountains. The river itself officially begins in Henderson Lake in Newcomb, New York...
and western New York. As eastern beaver populations were depleted, French and American trappers pushed west. In fact, 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
California Gold Rush
The California Gold Rush began on January 24, 1848, when gold was found by James W. Marshall at Sutter's Mill in Coloma, California. The first to hear confirmed information of the gold rush were the people in Oregon, the Sandwich Islands , and Latin America, who were the first to start flocking to...
, there was an earlier 19th century California Fur Rush
California Fur Rush
Before the 1849 California Gold Rush, American, English and Russian fur hunters were drawn to Spanish California in a California Fur Rush, to exploit its enormous fur resources...
which drove the earliest American settlement in that State. During the approximately 30 years (1806–1838) of the era of the Mountain Man
Mountain man
Mountain men were trappers and explorers who roamed the North American Rocky Mountains from about 1810 through the 1880s where they were instrumental in opening up the various Emigrant Trails allowing Americans in the east to settle the new territories of the far west by organized wagon trains...
, 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; however this is still a fraction of the originally estimated 100 to 200 million North American beaver before the days of the fur trade
Fur trade
The fur trade is a worldwide industry dealing in the acquisition and sale of animal fur. Since the establishment of world market for in the early modern period furs of boreal, polar and cold temperate mammalian animals have been the most valued...
.
These animals are considered pest
Pest (animal)
A pest is an animal which is detrimental to humans or human concerns. It is a loosely defined term, often overlapping with the related terms vermin, weeds, parasites and pathogens...
s in some parts of their range because their dams can cause flooding in nearby areas. Because they are persistent in repairing any damage to the dam, they were historically relocated or exterminated. However, non-lethal methods of containing beaver-related flooding have been developed. One such flow device
Flow device
Flow devices are man-made solutions to beaver-related flooding problems. Traditional solutions have been focused on the trapping and removal of all the beavers in the area...
has been utilized by both the Canadian and U.S. governments, called "Beaver Deceivers," or levelers, invented and pioneered by wildlife biologist, Skip Lisle.
The beaver is a keystone species
Keystone species
A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. Such species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and...
, increasing biodiversity in its territory through creation of beaver ponds and wetlands. As wetlands are formed and riparian habitats enlarged, aquatic plants colonize newly available watery habitat. Insect, invertebrate, fish, mammal, and bird diversity are also expanded.
Effects on stream flows and water quality
Beaver ponds increase stream flows in seasonally dry streams by storing run-off in the rainy season, which raises groundwater tables via percolation from beaver ponds. In a recent study using 12 serial aerial photo mosaics from 1948 to 2002, the impact of the return of beaver on open water area in east-central AlbertaAlberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
, Canada found that the mammals were associated with a 9-fold increase in open water area. Beaver returned to the area in 1954 after a long absence since their extirpation by the fur trade in the nineteenth century. Even during drought years, where beaver were present, there was 60 per cent more open water than those same areas during previous drought periods when beaver were absent. The authors concluded that beaver have a dramatic influence on the creation and maintenance of wetlands even during extreme drought.
From streams from the Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
coastal plain in the east to Lake Tahoe
Lake Tahoe
Lake Tahoe is a large freshwater lake in the Sierra Nevada of the United States. At a surface elevation of , it is located along the border between California and Nevada, west of Carson City. Lake Tahoe is the largest alpine lake in North America. Its depth is , making it the USA's second-deepest...
in the west, beaver ponds have been shown to remove sediment and pollutants including total suspended solids, total nitrogen, phosphates, carbon and silicates, improving stream water quality. In addition, fecal coliform and streptococci bacteria excreted into streams by grazing cattle are reduced by beaver ponds, where slowing currents lead to settling of the bacteria in bottom sediments.
The term "beaver fever" is a misnomer coined by the American press in the 1970s, following findings that the parasite Giardia lamblia
Giardia lamblia
Giardia lamblia is a flagellated protozoan parasite that colonizes and reproduces in the small intestine, causing giardiasis. The giardia parasite attaches to the epithelium by a ventral adhesive disc, and reproduces via binary fission...
, which causes Giardiasis
Giardiasis
Giardiasis or beaver fever in humans is a diarrheal infection of the small intestine by a single-celled organism Giardia lamblia. Giardiasis occurs worldwide with a prevalence of 20–30% in developing countries. In the U.S., 20,000 cases are reported to the CDC annually, but the true annual...
, is carried by beavers. However, further research has shown that the many animals and birds carry this parasite, and the major source of water contamination is by other humans. Recent concerns point to domestic animals as a significant vector of giardia with young calves in dairy herds testing as high as 100% positive for giardia. In addition, fecal coliform and streptococci bacteria excreted into streams by grazing cattle have been shown to be reduced by beaver ponds, where the bacteria are trapped in bottom sediments. In fact, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
has giardia outbreaks but no beaver, whereas Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
has plenty of beaver but had no giardia outbreaks until recently (in a southern part of Norway densely populated by humans but no beaver).
Effects on bird diversity
Trumpeter swanTrumpeter Swan
The Trumpeter Swan, Cygnus buccinator, is the largest native North American bird, if measured in terms of weight and length, and is the largest living waterfowl species on earth. It is the North American counterpart of the European Whooper Swan.-Description:Males typically measure from and weigh...
s (Cygnus buccinator) and Canada geese
Canada Goose
The Canada Goose is a wild goose belonging to the genus Branta, which is native to arctic and temperate regions of North America, having a black head and neck, white patches on the face, and a brownish-gray body....
(Branta canadensis) often depend on beaver lodges as nesting sites. Canada's small trumpeter swan population was observed not to nest on large lakes, preferring instead to nest on the smaller lakes and ponds associated with beaver activity.
Beaver may benefit the birds frequenting their ponds in several additional ways. Removal of some pondside trees by beavers would increase the density and height of the grass–forb–shrub layer, which enhances waterfowl nesting cover adjacent to ponds. Both forest gaps where trees had been felled by beaver and a "gradual edge" described as a complex transition from pond to forest with intermixed grasses, forbs, saplings, and shrubs are strongly associated with greater migratory bird species richness and abundance. Coppicing
Coppicing
Coppicing is a traditional method of woodland management which takes advantage of the fact that many trees make new growth from the stump or roots if cut down. In a coppiced wood, young tree stems are repeatedly cut down to near ground level...
of waterside willows and cottonwoods by beavers leads to dense shoot production which provides important cover for birds and the insects they feed on.
As trees are drowned by rising beaver impoundments they become ideal nesting sites for woodpeckers, who carve cavities that attract many other bird species including flycatchers
Empidonax
The genus Empidonax is a group of small insect-eating passerine birds in the tyrant flycatcher family, the Tyrannidae.Most of these birds are remarkably similar in plumage: olive on the upper parts with light underparts, eye rings and wing bars...
(Empidonax spp.), tree swallow
Tree Swallow
The Tree Swallow, Tachycineta bicolor, is a migratory passerine bird that breeds in North America and winters in Mexico, Central America and the Caribbean. It is a very rare vagrant to western Europe....
s (Tachycineta bicolor), tits (Paridae spp.), wood duck
Wood Duck
The Wood Duck or Carolina Duck is a species of duck found in North America. It is one of the most colourful of North American waterfowl.-Description:...
s (Aix sponsa), goldeneye
Goldeneye (duck)
Goldeneye are small tree-hole nesting northern hemisphere seaducks belonging to the genus Bucephala. Their plumage is black and white, and they eat fish, crustaceans and other marine life....
s (Bucephala spp.), mergansers (Mergus spp.), owl
Owl
Owls are a group of birds that belong to the order Strigiformes, constituting 200 bird of prey species. Most are solitary and nocturnal, with some exceptions . Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish...
s (Titonidae, Strigidae) and American kestrel
American Kestrel
The American Kestrel , sometimes colloquially known as the Sparrow Hawk, is a small falcon, and the only kestrel found in the Americas. It is the most common falcon in North America, and is found in a wide variety of habitats. At long, it is also the smallest falcon in North America...
s (Falco sparverius). Piscivores, including heron
Heron
The herons are long-legged freshwater and coastal birds in the family Ardeidae. There are 64 recognised species in this family. Some are called "egrets" or "bitterns" instead of "heron"....
s (Ardea spp.), grebe
Grebe
A grebe is a member of the Podicipediformes order, a widely distributed order of freshwater diving birds, some of which visit the sea when migrating and in winter...
s (Podicipedidae), cormorant
Cormorant
The bird family Phalacrocoracidae is represented by some 40 species of cormorants and shags. Several different classifications of the family have been proposed recently, and the number of genera is disputed.- Names :...
s (Phalacrocorax ssp.), American bittern
American Bittern
The American Bittern is a wading bird of the heron family Ardeidae. New evidence has led the American Ornithologists' Union to move the heron family into the order Pelecaniformes .-Description:...
s (Botaurus lentiginosa), great egret
Great Egret
The Great Egret , also known as the Great White Egret or Common Egret, White Heron, or Great White Heron, is a large, widely-distributed egret. Distributed across most of the tropical and warmer temperate regions of the world, in southern Europe it is rather localized...
(Ardea alba), snowy egret
Snowy Egret
The Snowy Egret is a small white heron. It is the American counterpart to the very similar Old World Little Egret, which has established a foothold in the Bahamas....
(Egretta thula), mergansers and belted kingfisher
Belted Kingfisher
The Belted Kingfisher is a large, conspicuous water kingfisher, the only member of that group commonly found in the northern United States and Canada. It is depicted on the 1986 series Canadian $5 note. All kingfishers were formerly placed in one family, Alcedinidae, but recent research suggests...
s (Megaceryle alcyon), utilize beaver ponds for fishing. Hooded merganser
Hooded Merganser
The Hooded Merganser is a small duck and is the only member of the genus Lophodytes.Hooded Mergansers have a crest at the back of the head which can be expanded or contracted. In adult males, this crest has a large white patch, the head is black and the sides of the duck are reddish-brown...
s (Lophodytes cucullatus), green heron
Green Heron
The Green Heron is a small heron of North and Central America. It was long considered conspecific with its sister species the Striated Heron , and together they were called "Green-backed Heron"...
(Butorides virescens), great blue heron
Great Blue Heron
The Great Blue Heron is a large wading bird in the heron family Ardeidae, common near the shores of open water and in wetlands over most of North and Central America as well as the West Indies and the Galápagos Islands. It is a rare vagrant to Europe, with records from Spain, the Azores and England...
(Ardea herodias) and belted kingfisher occurred more frequently in New York wetlands where beaver were active than at sites with no beaver activity.
Effects on trout and salmon
Beaver ponds have been shown to have a beneficial effect on trout and salmon populations, in fact many authors believe that the decline of salmonid fishes is related to the decline in beaver populations. Research in the Stillaguamish RiverStillaguamish River
The Stillaguamish River is a river in northwest Washington in the United States. It is mainly composed of two forks, the longer North Fork Stillaguamish and the South Fork Stillaguamish. The two forks join near Arlington. From there the Stillaguamish River proper flows for to Puget Sound...
basin in Washington state, found that extensive loss of beaver ponds resulted in an 89% reduction in coho salmon
Coho salmon
The Coho salmon, Oncorhynchus kisutch, is a species of anadromous fish in the salmon family. Coho salmon are also known as silver salmon or "silvers". It is the state animal of Chiba, Japan.-Description:...
(Oncorhynchus kisutch) smolt summer production and an almost equally detrimental 86% reduction in critical winter habitat carrying capacity
Carrying capacity
The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment...
. Swales and Leving had previously shown on the Coldwater River
Coldwater River (British Columbia)
The Coldwater River is located in south central British Columbia, Canada. It is the largest tributary of the Nicola River, joining it at the city of Merritt. Its traditional native name is Ntstlatko ....
in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
that off-channel beaver ponds were preferentially populated by coho salmon over other salmonids and provided overwintering protection, protection from high summer snowmelt flows and summer coho rearing habitat. The presence of beaver dams has also been shown to either increase the number of fish, their size, or both, in a study of brook trout
Brook trout
The brook trout, Salvelinus fontinalis, is a species of fish in the salmon family of order Salmoniformes. In many parts of its range, it is known as the speckled trout or squaretail. A potamodromous population in Lake Superior are known as coaster trout or, simply, as coasters...
(Salvelinus fontinalis), rainbow trout
Rainbow trout
The rainbow trout is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America. The steelhead is a sea run rainbow trout usually returning to freshwater to spawn after 2 to 3 years at sea. In other words, rainbow trout and steelhead trout are the same species....
(Oncorhynchus mykiss) and brown trout
Brown trout
The brown trout and the sea trout are fish of the same species....
(Salmo trutta) in Sagehen Creek, which flows into the Little Truckee River
Little Truckee River
The Little Truckee River is a river that is a tributary to its larger counterpart, the Truckee River, located in Nevada County in eastern California.-Description:...
at an altitude of 5,800 feet in the northern Sierra Nevada. These findings are consistent with a study of small streams in Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, that found that brown trout were larger in beaver ponds compared with those in riffle
Riffle
A Riffle is a short, relatively shallow and coarse-bedded length of stream over which the stream flows at higher velocity and higher turbulence than it normally does in comparison to a pool....
sections, and that beaver ponds provide habitat for larger trout in small streams during periods of drought. Similarly, brook trout, coho salmon and sockeye salmon
Sockeye salmon
Sockeye salmon , also called red salmon or blueback salmon in the USA, is an anadromous species of salmon found in the Northern Pacific Ocean and rivers discharging into it...
(Oncorhynchus nerka) were significantly larger in beaver ponds than those in un-impounded stream sections in Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
and Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
. Contrary to popular myth, most beaver dams do not pose barriers to trout and salmon migration, although they may be restricted seasonally during periods of low stream flows. Rainbow, brown and brook trout have been shown to cross as many as 14 consecutive beaver dams. Both adults and juveniles of coho salmon, steelhead trout, sea run cutthroat
Coastal cutthroat trout
The coastal cutthroat trout also known as the sea run cutthroat, or harvest trout are a subspecies of cutthroat trout with an anadromous life history....
(Oncorhyncus clarki clarki), Dolly Varden trout
Dolly Varden trout
The Dolly Varden trout, Salvelinus malma malma, is a subspecies of anadromous fish in the salmon family, and is technically a char. Although many of the fish are anadromous, the fish also exists in landlocked waters.- Range :The subspecies S. m...
(Salvelinus malma malma), and sockeye salmon are able to cross beaver dams. In southeast Alaska, coho jumped dams as high as 2 meters, were found above all beaver dams and had their highest densities in streams with beaver. In Oregon coastal streams, beaver dams are ephemeral and almost all wash out in high winter flows only to be re-built every summer. Migration of adult Atlantic salmon
Atlantic salmon
The Atlantic salmon is a species of fish in the family Salmonidae, which is found in the northern Atlantic Ocean and in rivers that flow into the north Atlantic and the north Pacific....
(Salmo salar) may be limited by beaver dams but the presence of juveniles upstream from the dams suggests that the dams are penetrated by parr. Downstream migration of Atlantic salmon smolts was similarly unaffected by beaver dams, even in periods of low flows. Two year old Atlantic salmon parr in beaver ponds in eastern Canada showed faster summer growth in length and mass and were in better condition than parr upstream or downstream from the pond. The importance of winter habitat to salmonids afforded by beaver ponds may be especially important (and underappreciated) in streams without deep pools or where ice cover makes contact with the bottom of shallow streams. Enos Mills wrote in 1913, "One dry winter the stream...ran low and froze to the bottom, and the only trout in it that survived were those in the deep holes of beaver ponds." Cutthroat trout
Cutthroat trout
The cutthroat trout is a species of freshwater fish in the salmon family of order Salmoniformes. It is one of the many fish species colloquially known as trout...
(Oncorhynchus clarki) and bull trout
Bull trout
The bull trout, Salvelinus confluentus, is a char of the family Salmonidae native to northwestern North America. Historically, S. confluentus has been known as the "Dolly Varden" , but was re-classified as a separate species in 1980. Bull trout are listed as a threatened species under the U.S....
(Salvelinus confluentus) were noted to overwinter in Montana beaver ponds, brook trout congregated in winter in New Brunswick and Wyoming beaver ponds, and coho salmon in Oregon beaver ponds. In 2011 a meta-analysis of studies of beaver impacts on salmonids found that beaver were a net benefit to salmon and trout populations primarily by improving habitat (building ponds) both for rearing and overwintering and that this conclusion was based over half the time on scientific data. In contrast, the most often cited negative impact of beavers on fishes were barriers to migration although that conclusion was based on scientific data only 29% of the time. They also found that when beaver dams do present barriers that these are generally short-lived, as the dams are overtopped or blown out by storm surges.
Efforts to restore salmonid habitat in the western United States have focused primarily on establishing large woody debris
Large Woody Debris
Large woody debris are the logs, sticks, branches, and other wood that falls into streams and rivers. This debris can influence the flow and the shape of the stream channel...
in streams to slow flows and create pools for young salmonids. However research in Washington state found that the average summer smolt production per beaver dam ranges from 527 to 1,174 fish, whereas the summer smolt production from a pool formed by instream large woody debris is about 6–15 individuals, suggesting that re-establishment of beaver populations would be 80 times more effective.
Recently, beaver have been discovered living in brackish water in estuarine tidal marshes, where Chinook salmon
Chinook salmon
The Chinook salmon, Oncorhynchus tshawytscha, is the largest species in the pacific salmon family. Other commonly used names for the species include King salmon, Quinnat salmon, Spring salmon and Tyee salmon...
(Oncorhynchus tshawytscha) densities were five times higher in beaver ponds than in neighboring areas.
Effects on riparian trees and vegetation
Conventional wisdom has held that beaver girdle and fell trees and that they diminish riparian trees and vegetation, but the opposite appears to be true when studies are conducted longer-term. In 1987, Beier reported that beaver had caused local extinction of Quaking aspen (Populus tremuloides) and Black cottonwood (Populus trichocarpa) on 4-5% of stream reaches on the lower Truckee RiverTruckee River
The Truckee River is a stream in the U.S. states of California and Nevada. The river is about long. Its endorheic drainage basin is about , of which about are in Nevada. The Truckee is the sole outlet of Lake Tahoe and drains part of the high Sierra Nevada, emptying into Pyramid Lake in the Great...
in the Sierra Nevada mountains, however Willow
Willow
Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...
(Salix spp.) responded by re-growing vigorously in most reaches. He further speculated that without control of beaver populations that aspen and cottonwood could go extinct on the Truckee River. However, not only have aspen and cottonwood survived ongoing beaver colonization but a recent study of ten Sierra Nevada streams in the Lake Tahoe
Lake Tahoe
Lake Tahoe is a large freshwater lake in the Sierra Nevada of the United States. At a surface elevation of , it is located along the border between California and Nevada, west of Carson City. Lake Tahoe is the largest alpine lake in North America. Its depth is , making it the USA's second-deepest...
basin utilizing aerial multispectral videography has shown that deciduous, thick herbaceous, and thin herbaceous vegetation are more highly concentrated near beaver dams, whereas coniferous trees are decreased. These findings are consistent with those of Pollock, who reported that in Bridge Creek, a stream in semi-arid eastern Oregon, the width of riparian vegetation on stream banks was increased several-fold as beaver dams watered previously dry terraces adjacent to the stream. In a second study of riparian vegetation based on observations of Bridge Creek over a 17 year time period, although portions of the study reach were periodically abandoned by beaver following heavy utilization of streamside vegetation, within a few years dense stands of woody plants of greater diversity occupied a larger portion of the floodplain. Although black cottonwood and thinleaf alder did not generally re-sprout after beaver cutting, they frequently grew from seeds landing on freshly exposed alluvial deposits secondary to beaver activity. Therefore, beaver appear to increase riparian vegetation given enough years to aggrade sediments and pond heights sufficiently to create widened, well-watered riparian zones, especially in areas of low summer rainfall.
The surface of beaver ponds are typically at or near bank-full, so even small increases in stream flows cause the pond to overflow its banks. Thus, high stream flows spread water and nutrients to beyond the stream banks to wide riparian zones when beaver dams are present.
Beavers and stream restoration
In the 1930s, the U.S. Government put 600 beaver to work alongside the Civilian Conservation CorpsCivilian Conservation Corps
The Civilian Conservation Corps was a public work relief program that operated from 1933 to 1942 in the United States for unemployed, unmarried men from relief families, ages 18–25. A part of the New Deal of President Franklin D...
in projects to stop soil erosion by streams in Oregon, Washington, Wyoming, and Utah. At the time it was estimated that each beaver, whose initial cost was about $5, completed work worth $300.
In a pilot study in Washington state, the Lands Council is reintroducing beavers to evaluate their projections that if 10,000 miles of suitable habitat were repopulated then 650 trillion gallons of spring runoff would be held back for release in the arid fall season. This project was developed in response to a 2003 Washington Department of Ecology
Washington Department of Ecology
The Washington Department of Ecology, or simply, Ecology, is an environmental regulatory agency for the State of Washington. The department administers laws and regulations pertaining to the areas of water quality, water rights and water resources, shoreline management, toxics clean-up, nuclear...
proposal to spend as much as ten billion dollars on construction of several dams on Columbia River
Columbia River
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...
tributaries to retain storm season runoff. The State of Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
published a Beaver Management Plan which includes re-establishing beavers in ten streams per year for the purpose of watershed restoration each year from 2010 through 2020.
Urban beavers
After 200 years, a beaver returned to New York CityNew York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
in 2007, making its home along the Bronx River
Bronx River
The Bronx River, approximately long, flows through southeast New York in the United States. It is named after colonial settler Jonas Bronck. The Bronx River is the only fresh water river in New York City....
, having spent time living at the Bronx Zoo
Bronx Zoo
The Bronx Zoo is located in the Bronx borough of New York City, within Bronx Park. It is the largest metropolitan zoo in the United States, comprising of park lands and naturalistic habitats, through which the Bronx River flows....
as well as the Botanical Gardens. Beavers have not lived in New York City since the early 19th century when trappers extirpated them completely from the state. The return of "Jose", named after Representative Jose Serrano from the Bronx, has been seen as evidence that efforts to restore the river have been successful. In the summer of 2010 a second beaver joined Jose, doubling the beaver population in New York City. Beaver were once important to the city's economy and a pair of beavers appears on the city's official seal and flag.
In Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
, several beavers have returned and made a home near the Lincoln Park
Lincoln Park
Lincoln Park is an urban park in Chicago, which gave its name to the Lincoln Park, Chicago community area.Lincoln Park may also refer to:-Urban parks:*Lincoln Park , California*Lincoln Park, San Francisco, California...
's North Pond. The "Lincoln Park Beaver" has not been as well received by the Chicago Park District
Chicago Park District
The Chicago Park District is the oldest and largest park district in the U.S.A, with a $385 million annual budget. It has the distinction of spending the most per capita on its parks, even more than Boston in terms of park expenses per capita...
and the Lincoln Park
Lincoln Park
Lincoln Park is an urban park in Chicago, which gave its name to the Lincoln Park, Chicago community area.Lincoln Park may also refer to:-Urban parks:*Lincoln Park , California*Lincoln Park, San Francisco, California...
Conservancy, which was concerned over damage to trees in the area. In March 2009, they hired an exterminator to remove a beaver family using live traps, and accidentally killed the mother when she got caught in a snare and drowned. Relocation costs $4,000-$4,500 per animal. Scott Garrow, District Wildlife Biologist with the Illinois Department of Natural Resources
Illinois Department of Natural Resources
The Illinois Department of Natural Resources is a cabinet-level department of the state government of Illinois. It is headquartered in the state capital of Springfield...
, opined that relocating the beavers may be "a waste of time", as there are records of beaver recolonizing North Pond in Lincoln Park in 1994, 2003, 2004, 2008 and 2009. As of fall 2009 a new beaver lodge has appeared on North Pond's northwest bank.
Outside San Francisco, in downtown Martinez, California
Martinez, California
Martinez is a city and the county seat of Contra Costa County, California, United States. The population was 35,824 at the 2010 census. The downtown is notable for its large number of preserved old buildings...
, a male and female beaver arrived in Alhambra Creek
Alhambra Creek
Alhambra Creek is a stream in Contra Costa County, California in Northern California which drains into the Carquinez Strait by way of the historical Arroyo del Hambre. Alhambra Creek and its valley take their name from Cañada del Hambre, Spanish for "valley of hunger", apparently because of some...
in 2006. The Martinez beavers built a dam 30 feet wide and at one time 6 feet high, and chewed through half the willows and other creekside landscaping the city planted as part of its $9.7 million 1999 flood-improvement project. When the City Council wanted to remove the beavers because of fears of flooding, local residents organized to protect them, forming an organization called "Worth a Dam". Resolution included installation of a flow device
Flow device
Flow devices are man-made solutions to beaver-related flooding problems. Traditional solutions have been focused on the trapping and removal of all the beavers in the area...
through the beaver dam
Beaver dam
Beaver dams are dams built by beavers as protection against predators such as coyotes, wolves, and bears, and to provide easy access to food during winter. Beavers work at night and are prolific builders, carrying mud and stones with their fore-paws and timber between their teeth...
so that the pond's water level could not become excessive. Now protected, the beaver have transformed Alhambra Creek from a trickle into multiple dams and beaver ponds, which in turn, lead to the return of steelhead trout and river otter in 2008, and mink
Mink
There are two living species referred to as "mink": the European Mink and the American Mink. The extinct Sea Mink is related to the American Mink, but was much larger. All three species are dark-colored, semi-aquatic, carnivorous mammals of the family Mustelidae, which also includes the weasels and...
in 2009. The Martinez beavers probably originated from the Sacramento-San Joaquin River Delta which once held the largest concentration of beaver in North America.
In 1999, Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....
's annual Cherry Blossom Festival
National Cherry Blossom Festival
The National Cherry Blossom Festival is a spring celebration in Washington, D.C., commemorating the March 27, 1912, gift of Japanese cherry trees from Mayor Yukio Ozaki of Tokyo to the city of Washington...
was plagued by a family of beavers who lived in the Tidal Basin
Tidal Basin
-External links:*-References:...
. The offenders were caught and removed, but not before damaging 14 cherry trees, including some of the largest and oldest trees.
As introduced non-native species
Tierra del Fuego
Tierra del Fuego is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of a main island Isla Grande de Tierra del Fuego divided between Chile and Argentina with an area of , and a group of smaller islands including Cape...
in southern Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
and Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, for commercial fur production. However, the project failed and the beavers, a few pairs, were released into the wild. Having no natural predators in their new environment, they quickly spread throughout the island, and to other islands in the region, reaching a number of 100,000 individuals within just 50 years. They are now considered a serious invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
in the region, due to their massive destruction of forest trees, and efforts are being made for their eradication. The drastically different ecosystem has led to substantial environmental damage, as the ponds created by the beavers have no ecological purpose (wetlands do not form there as they do in the beavers' native territory) and there are no native, large predators. They have also been found to cross saltwater to islands northward; a possible encroachment on the mainland has naturalists highly concerned.
In contrast, areas with introduced beaver were associated with increased populations of native puye
Common galaxias
The common galaxias or the inanga , is a species of fish from the galaxiid family that is very widespread in the southern hemisphere. It is a slim narrow fish with a forked tail and as an adult it lives in freshwater rivers and lakes. Common galaxias grows to a length of 40 to 120 mm, but can grow...
fish (Galaxias maculatus), whereas the exotic brook trout
Brook trout
The brook trout, Salvelinus fontinalis, is a species of fish in the salmon family of order Salmoniformes. In many parts of its range, it is known as the speckled trout or squaretail. A potamodromous population in Lake Superior are known as coaster trout or, simply, as coasters...
(Salvelinus fontinalis) and rainbow trout
Rainbow trout
The rainbow trout is a species of salmonid native to tributaries of the Pacific Ocean in Asia and North America. The steelhead is a sea run rainbow trout usually returning to freshwater to spawn after 2 to 3 years at sea. In other words, rainbow trout and steelhead trout are the same species....
(Oncorhynchus mykiss) had negative impacts on native stream fishes in the Cape Horn Biosphere Reserve
Cape Horn Biosphere Reserve
The Cape Horn Biosphere Reserve is located in the extreme south of Chile and comprises marine areas, islands, fjords, channels, forests and moorland. It covers an area of approximately 49,000 km²...
, Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
.
As food
Beaver meat is similar tasting to lean beefBeef
Beef is the culinary name for meat from bovines, especially domestic cattle. Beef can be harvested from cows, bulls, heifers or steers. It is one of the principal meats used in the cuisine of the Middle East , Australia, Argentina, Brazil, Europe and the United States, and is also important in...
, but care must be taken to prevent contamination from the animal's strong castor (musk
Musk
Musk is a class of aromatic substances commonly used as base notes in perfumery. They include glandular secretions from animals such as the musk deer, numerous plants emitting similar fragrances, and artificial substances with similar odors. Musk was a name originally given to a substance with a...
) gland. It is usually slow-cooked in a broth, and was a valuable food source to Native Americans
Indigenous peoples of the Americas
The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...
. Early French Canadian Catholics considered beaver to be "four-legged fish" that could be eaten at Lent.
Despite their name, the fried pastries found in parts of Canada called beaver tails
Beaver tail (pastry)
BeaverTails are a Canadian-based chain of pastry stands operated by BeaverTails Canada Inc. The chain's namesake product is a line of fried dough pastries, individually hand stretched to resemble a beaver’s tail...
contain no beaver.
Symbolism
As the national animal and one of the national symbols of Canada, the beaver is depicted on the Canadian five-cent pieceNickel (Canadian coin)
The Canadian five-cent coin, commonly called a nickel, is a coin worth five cents or one-twentieth of a Canadian dollar. It was patterned on the corresponding coin in the neighbouring United States...
and was on the first Canadian postage stamp, the Three Penny Beaver. It is also the state animal of Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
and New York, and a common school emblem for engineering
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
schools, including the California Institute of Technology
California Institute of Technology
The California Institute of Technology is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering...
, the Massachusetts Institute of Technology
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
, and the University of Alberta
University of Alberta
The University of Alberta is a public research university located in Edmonton, Alberta, Canada. Founded in 1908 by Alexander Cameron Rutherford, the first premier of Alberta and Henry Marshall Tory, its first president, it is widely recognized as one of the best universities in Canada...
as well as the mascot for Oregon State University
Oregon State University
Oregon State University is a coeducational, public research university located in Corvallis, Oregon, United States. The university offers undergraduate, graduate and doctoral degrees and a multitude of research opportunities. There are more than 200 academic degree programs offered through the...
, Babson College
Babson College
Babson College is a private business school located in Wellesley, Massachusetts near Boston.- History :Babson College was founded by Roger Babson on September 3, 1919, as the Babson Institute. It was renamed "Babson College" in 1969...
, and the City College of New York
City College of New York
The City College of the City University of New York is a senior college of the City University of New York , in New York City. It is also the oldest of the City University's twenty-three institutions of higher learning...
. The beaver also appears in the coats of arms
Coat of arms
A coat of arms is a unique heraldic design on a shield or escutcheon or on a surcoat or tabard used to cover and protect armour and to identify the wearer. Thus the term is often stated as "coat-armour", because it was anciently displayed on the front of a coat of cloth...
of the Hudson's Bay Company
Hudson's Bay Company
The Hudson's Bay Company , abbreviated HBC, or "The Bay" is the oldest commercial corporation in North America and one of the oldest in the world. A fur trading business for much of its existence, today Hudson's Bay Company owns and operates retail stores throughout Canada...
, University of Toronto
University of Toronto
The University of Toronto is a public research university in Toronto, Ontario, Canada, situated on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution of higher learning in Upper Canada...
, Wilfrid Laurier University
Wilfrid Laurier University
Wilfrid Laurier University is a university located in Waterloo, Ontario, Canada. It also has campuses in Brantford, Ontario, Kitchener, Ontario and Toronto, Ontario and a future proposed campus in Milton, Ontario. It is named in honour of Sir Wilfrid Laurier, the seventh Prime Minister of Canada....
, and the London School of Economics
London School of Economics
The London School of Economics and Political Science is a public research university specialised in the social sciences located in London, United Kingdom, and a constituent college of the federal University of London...
.
Much of the early economy of New Netherland
New Netherland
New Netherland, or Nieuw-Nederland in Dutch, was the 17th-century colonial province of the Republic of the Seven United Netherlands on the East Coast of North America. The claimed territories were the lands from the Delmarva Peninsula to extreme southwestern Cape Cod...
was based on the beaver fur trade
Fur trade
The fur trade is a worldwide industry dealing in the acquisition and sale of animal fur. Since the establishment of world market for in the early modern period furs of boreal, polar and cold temperate mammalian animals have been the most valued...
. As such, the seal of New Netherland featured the beaver; likewise, the coats of arms of Albany, New York
Coat of arms of Albany, New York
The coat of arms of Albany, New York, is the heraldic symbol representing the city of Albany, the capital of the U.S. state of New York. The coat of arms is rarely seen by itself; it is almost always used in the city seal or on the city flag...
and New York City
Seal of New York City
The seal of the city of New York, adopted in an earlier form in 1686, bears the legend SIGILLUM CIVITATIS NOVI EBORACI which means simply "The Seal of the City of New York": Eboracum was the Roman name for York, the titular seat of James II as Duke of York....
included the beaver.
External links
- Ecology of the Beaver
- The romance of the beaver; being the history of the beaver in the western hemisphere, by A. Radclyffe Dugmore. Illustrated with photographs from life and drawings by the author. Publisher: Philadelphia, J.B. Lippincott company; London, W. Heinemann 1914 (a searchable facsimile at the University of Georgia Libraries)
- "Worth a Dam" (beaver information and educational site)
- The Beaver A Keystone Species, a short video by Mike Foster