Beaver
Overview
 
The beaver is a primarily nocturnal
Nocturnal animal
Nocturnality is an animal behavior characterized by activity during the night and sleeping during the day. The common adjective is "nocturnal"....

, large, semi-aquatic rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

. Castor includes two extant species, North American Beaver (Castor canadensis) (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 Eurasian Beaver (Castor fiber) (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...

). Beavers are known for building dams, canals, and lodges (homes). They are the second-largest rodent in the world (after the 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...

). Their colonies create one or more dams to provide still, deep water to protect against predators, and to float food and building material.
Encyclopedia
The beaver is a primarily nocturnal
Nocturnal animal
Nocturnality is an animal behavior characterized by activity during the night and sleeping during the day. The common adjective is "nocturnal"....

, large, semi-aquatic rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

. Castor includes two extant species, North American Beaver (Castor canadensis) (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 Eurasian Beaver (Castor fiber) (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...

). Beavers are known for building dams, canals, and lodges (homes). They are the second-largest rodent in the world (after the 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...

). Their colonies create one or more dams to provide still, deep water to protect against predators, and to float food and building material. The North American beaver population was once more than 60 million, but as of 1988 was 6–12 million. This population decline is due to extensive hunting for fur, for glands used as medicine and perfume, and because their harvesting of trees and flooding of waterways may interfere with other land uses.

General

Beavers are known for their natural trait of building dams on rivers and streams, and building their homes (known as "lodges") in the resulting pond. Beavers also build canals to float build materials that are difficult to haul over land. They use powerful front teeth to cut trees and other plants that they use both for building and for food. In the absence of existing ponds, beavers must construct dams before building their lodges. First they place vertical poles, then fill between the poles with a crisscross of horizontally placed branches. They fill in the gaps between the branches with a combination of weeds and mud until the dam impounds sufficient water to surround the lodge.
They are known for their alarm signal: when startled or frightened, a swimming beaver will rapidly dive while forcefully slapping the water with its broad tail, audible over great distances above and below water. This serves as a warning to beavers in the area. Once a beaver has sounded the alarm, nearby beavers will dive and may not reemerge for some time. Beavers are slow on land, but are good swimmers, and can stay under water for as long as 15 minutes.

Beavers are herbivores, and prefer the wood of quaking aspen, cottonwood, 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...

, alder
Alder
Alder is the common name of a genus of flowering plants belonging to the birch family . The genus comprises about 30 species of monoecious trees and shrubs, few reaching large size, distributed throughout the North Temperate Zone and in the Americas along the Andes southwards to...

, birch
Birch
Birch is a tree or shrub of the genus Betula , in the family Betulaceae, closely related to the beech/oak family, Fagaceae. The Betula genus contains 30–60 known taxa...

, maple
Maple
Acer is a genus of trees or shrubs commonly known as maple.Maples are variously classified in a family of their own, the Aceraceae, or together with the Hippocastanaceae included in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group system, favour inclusion in...

 and cherry
Cherry
The cherry is the fruit of many plants of the genus Prunus, and is a fleshy stone fruit. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium....

 trees. They also eat sedges, pondweed, and water lilies.

Beavers do not hibernate, but store sticks and logs in a pile in their ponds, eating the underbark. Some of the pile is generally above water and accumulates snow in the winter. This insulation of snow often keeps the water from freezing in and around the food pile, providing a location where beavers can breathe when outside their lodge.

Fossil remains of beavers are found in the peat and other superficial deposits of Britain and the continent of Europe; while in the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 formations of Britain and Siberia, occur remains of a giant extinct beaver, Trogontherium cuvieri, representing a genus by itself.

Beavers have webbed hind-feet, and a broad, scaly tail. They have poor eyesight, but keen senses of hearing, smell, and touch. A beaver's teeth grow continuously so that they will not be worn down by chewing on wood. Their four incisors are composed of hard orange enamel on the front and a softer dentin
Dentin
Dentine is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth. Usually, it is covered by enamel on the crown and cementum on the root and surrounds the entire pulp...

 on the back. The chisel-like ends of incisors are maintained by their self-sharpening wear pattern.

Beavers continue to grow throughout life. Adult specimens weighing over 25 kg (55.1 lb) are not uncommon. Females are as large as or larger than males of the same age, which is uncommon among mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s. Beavers live up to 24 years of age in the wild.

Etymology

The word is descended from the Proto-Indo-European
Proto-Indo-European language
The Proto-Indo-European language is the reconstructed common ancestor of the Indo-European languages, spoken by the Proto-Indo-Europeans...

 name of the animal, cf. Sanskrit babhru's, brown, Lat.
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 fiber, Ger.
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....

 Biber, Russ.
Russian language
Russian is a Slavic language used primarily in Russia, Belarus, Uzbekistan, Kazakhstan, Tajikistan and Kyrgyzstan. It is an unofficial but widely spoken language in Ukraine, Moldova, Latvia, Turkmenistan and Estonia and, to a lesser extent, the other countries that were once constituent republics...

 bobr; the root bhru has given "brown
Brown
Brown is a color term, denoting a range of composite colors produced by a mixture of orange, red, rose, or yellow with black or gray. The term is from Old English brún, in origin for any dusky or dark shade of color....

", and, through Romanic
Romance languages
The Romance languages are a branch of the Indo-European language family, more precisely of the Italic languages subfamily, comprising all the languages that descend from Vulgar Latin, the language of ancient Rome...

, "bronze
Bronze
Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...

" and "burnish
Burnish
Burnishing is a form of pottery treatment in which the surface of the pot is polished, using a hard smooth surface such as a wooden or bone spatula, smooth stones, plastic, or even glass bulbs, while it still is in a leathery 'green' state, i.e., before firing. After firing, the surface is...

".

Species

They are the only extant members of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Castoridae
Castoridae
The family Castoridae contains the two living species of beaver and their fossil relatives. This was once a highly diverse group of rodents, but is now restricted to a single genus, Castor.- Characteristics :...

, which contains a single genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, Castor. Genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 research
Research
Research can be defined as the scientific search for knowledge, or as any systematic investigation, to establish novel facts, solve new or existing problems, prove new ideas, or develop new theories, usually using a scientific method...

 has shown the European and North American beaver populations to be distinct species and that hybridization is unlikely. Beavers are closely related to squirrel
Squirrel
Squirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots , flying squirrels, and prairie dogs. Squirrels are indigenous to the Americas, Eurasia, and Africa and have been introduced to Australia...

s (Sciuridae), agreeing in certain structural peculiarities of the lower jaw and skull. In the Sciuridae the two main bones (tibia and fibula) of the lower half of the leg are quite separate, the tail is round and hairy, and the habitats are arboreal and terrestrial. In the beavers or Castoridae these bones are in close contact at their lower ends, the tail is depressed, expanded and scaly, and their habitats are aquatic.

Although superficially similar to each other, there are several important differences between the two species. Eurasian beavers tend to be bigger, with larger, less rounded heads, longer, narrower muzzles, thinner, shorter and lighter underfur, narrower, less oval-shaped tails and shorter shin bones, making them less capable of bipedal locomotion than the North American species. Eurasian beavers have longer nasal bones than their North American cousins, with the widest point being at the end of the snout for the former, and in the middle for the latter. The nasal opening for the Eurasian species is triangular, unlike that of the North American race which is square. The foramen magnum is rounded in the Eurasian beaver, and triangular in the North American. The anal glands of the Eurasian beaver are larger and thin-walled with a large internal volume compared to that of the North American breed. Finally, the guard hairs of the Eurasian beaver have a longer hollow medulla at their tips. Fur colour is also different. Overall, 66% of Eurasian beavers have pale brown or beige fur, 20% have reddish brown, nearly 8% are brown and only 4% have blackish coats. In North American beavers, 50% have pale brown fur, 25% are reddish brown, 20% are brown and 6% are blackish.

The two species are not genetically compatible. North American beavers have 40 chromosomes, while Eurasian 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.

Eurasian Beaver

The Eurasian Beaver (Castor fiber) was nearly hunted to extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 in Europe, both for fur and for 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...

, a secretion of its scent gland believed to have medicinal properties. However, the beaver is now being re-introduced throughout Europe. Several thousand live on the Elbe
Elbe
The Elbe is one of the major rivers of Central Europe. It rises in the Krkonoše Mountains of the northwestern Czech Republic before traversing much of Bohemia , then Germany and flowing into the North Sea at Cuxhaven, 110 km northwest of Hamburg...

, the Rhone
Rhône River
The Rhone is one of the major rivers of Europe, rising in Switzerland and running from there through southeastern France. At Arles, near its mouth on the Mediterranean Sea, the river divides into two branches, known as the Great Rhone and the Little Rhone...

 and in parts of Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...

. A thriving community lives in northeast Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

, and the Eurasian Beaver also returned to the Morava River banks in Slovakia
Slovakia
The Slovak Republic is a landlocked state in Central Europe. It has a population of over five million and an area of about . Slovakia is bordered by the Czech Republic and Austria to the west, Poland to the north, Ukraine to the east and Hungary to the south...

 and the Czech Republic
Czech Republic
The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

. They have been reintroduced
Reintroduction
Reintroduction is the deliberate release of a species into the wild in zones formerly inhabited by said species but where it has disappeared from for a number of reasons, from captivity or relocated from other areas where the species still survives in...

 in Scotland (Knapdale
Knapdale
Knapdale forms a rural district of Argyll and Bute in the Scottish Highlands, adjoining Kintyre to the south, and divided from the rest of Argyll to the north by the Crinan Canal. It includes two parishes, North Knapdale and South Knapdale....

), Bavaria
Bavaria
Bavaria, formally the Free State of Bavaria is a state of Germany, located in the southeast of Germany. With an area of , it is the largest state by area, forming almost 20% of the total land area of Germany...

, Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

, Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

, Serbia
Serbia
Serbia , officially the Republic of Serbia , is a landlocked country located at the crossroads of Central and Southeast Europe, covering the southern part of the Carpathian basin and the central part of the Balkans...

 (Zasavica
Zasavica (bog)
The Zasavica is a bog in the region of Mačva, west-central Serbia. With Obedska bara and Carska Bara one of the major wildlife refuges and one of the last authentically preserved wetlands in Serbia...

 bog), Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

 (West Jutland
Jutland
Jutland , historically also called Cimbria, is the name of the peninsula that juts out in Northern Europe toward the rest of Scandinavia, forming the mainland part of Denmark. It has the North Sea to its west, Kattegat and Skagerrak to its north, the Baltic Sea to its east, and the Danish–German...

) and Bulgaria
Bulgaria
Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

 and are spreading to new locations. The beaver became extinct in Great Britain in the sixteenth century: Giraldus Cambrensis
Giraldus Cambrensis
Gerald of Wales , also known as Gerallt Gymro in Welsh or Giraldus Cambrensis in Latin, archdeacon of Brecon, was a medieval clergyman and chronicler of his times...

 reported in 1188 (Itinerarium ii.iii) that it was to be found only in the Teifi in Wales and in one river in Scotland, though his observations are clearly second hand. In October 2005, six Eurasian beavers were reintroduced to Britain in Lower Mill Estate in Gloucestershire
Gloucestershire
Gloucestershire is a county in South West England. The county comprises part of the Cotswold Hills, part of the flat fertile valley of the River Severn, and the entire Forest of Dean....

; in July 2007 a colony of four Eurasian beavers was established at Martin Mere
Martin Mere
Martin Mere is a mere near Burscough, Lancashire, England on the West Lancashire Coastal Plain. The mere is a vast marsh, around that, until it was drained, was the largest body of fresh water in England.-History:...

 in Lancashire
Lancashire
Lancashire is a non-metropolitan county of historic origin in the North West of England. It takes its name from the city of Lancaster, and is sometimes known as the County of Lancaster. Although Lancaster is still considered to be the county town, Lancashire County Council is based in Preston...

, and a trial re-introduction occurred in Scotland in May 2009. Feasibility studies for a reintroduction to Wales are at an advanced stage and a preliminary study for a reintroduction of beavers to the wild in England has recently been published.

North American Beaver

The North American Beaver (Castor canadensis), also called the Canadian Beaver (which is also the name of a subspecies), American Beaver, or simply Beaver in North America, is native to Canada, much of the United States and parts of northern Mexico. The chief feature distinguishing C. canadensis from C. fiber is the form of the nasal bones of the skull. This species was introduced to the Argentine and Chilean Tierra del Fuego, as well as Finland, France, Poland and Russia.

The North American beaver's preferred food is the water-lily (Nuphar luteum), which bears a resemblance to a cabbage-stalk, and grows at the bottom of lakes and rivers. Beavers also gnaw the bark of birch
Birch
Birch is a tree or shrub of the genus Betula , in the family Betulaceae, closely related to the beech/oak family, Fagaceae. The Betula genus contains 30–60 known taxa...

, poplar
Poplar
Populus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....

, and 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...

 trees; but during the summer a more varied herbage, with the addition of berries, is consumed.
These animals are often trapped for their fur. During the early 19th century, trapping eliminated this animal from large portions of its original range. However, through trap and transfer and habitat conservation
Habitat conservation
Habitat conservation is a land management practice that seeks to conserve, protect and restore, habitat areas for wild plants and animals, especially conservation reliant species, and prevent their extinction, fragmentation or reduction in range...

 it made a nearly complete recovery by the 1940s. Beaver reintroduction in British Columbia was facilitated by Eric Collier as recounted in his book Three Against the Wilderness. Beaver furs were used to make clothing and top-hats. Much of the early exploration of North America was driven by the quest for this animal's fur.

Native peoples and early settlers also ate this animal's meat. The current beaver population has been estimated to be 10 to 15 million; one estimate claims that there may at one time have been as many as 90 million.

Habitat

The habitat of the beaver is the riparian zone
Riparian zone
A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the fifteen terrestrial biomes of the earth. Plant habitats and communities along the river margins and banks are called riparian vegetation, characterized by...

, inclusive of stream bed. The actions of beavers for hundreds of thousands of years in the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

 have kept these watery systems healthy and in good repair, although a human observing all the downed trees might think that the beavers were doing just the opposite.

The beaver works as 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...

 in an ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

 by creating wetlands that are used by many other species. Next to humans, no other extant animal appears to do more to shape its landscape.

Beavers fell trees for several reasons. They fell large mature trees, usually in strategic locations, to form the basis of a dam, but European beavers tend to use small diameter (<10 cm) trees for this purpose. Beavers fell small trees, especially young second-growth trees, for food. Broadleaved trees re-grow as a coppice, providing easy-to-reach stems and leaves for food in subsequent years. Ponds created by beavers can also kill some tree species by drowning but this creates standing dead wood, which is very important for a wide range of animals and plants.

Dams

Beaver dams are created as a protection against predators, such as coyotes, wolves and bears, and to provide easy access to food during winter. Beavers always work at night and are prolific builders, carrying mud and stones with their fore-paws and timber between their teeth. Because of this, destroying a beaver dam without removing the beavers is difficult, especially if the dam is downstream of an active lodge. Beavers can rebuild such primary dams overnight, though they may not defend secondary dams as vigorously. (Beavers may create a series of dams along a river.)

Lodges


The ponds created by well-maintained dams help isolate the beavers' homes, their lodges, which are created from severed branches and mud. The beavers cover their lodges late every autumn with fresh mud, which freezes when the frost sets in. The mud becomes almost as hard as stone, and neither wolves
Gray Wolf
The gray wolf , also known as the wolf, is the largest extant wild member of the Canidae family...

 nor 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 can penetrate it.

The lodge has underwater entrances to make entry nearly impossible for any other animal (however, muskrats have been seen living inside beaver lodges with the beavers who made them). A very small amount of the lodge is actually used as a living area. Contrary to popular belief, beavers actually dig out their dens with underwater entrances after they finish building the dams and lodge structures. There are typically two dens within the lodge, one for drying off after exiting the water, and another, drier one where the family actually lives.
Beaver houses are formed of the same materials as the dams, with little order or regularity of structure, and seldom contain more than four adult and six or eight young beavers. Some of the larger houses have one or more partitions, but these are only posts of the main building left by the builders to support the roof, for the apartments usually have no communication with each other except by water.

When the ice breaks up in spring beavers always leave their embankments and rove about until just before fall, when they return to their old habitations and lay in their winter stock of wood. They seldom begin to repair the houses until the frost sets in, and never finish the outer coating until the cold becomes severe. When they erect a new habitation they fell the wood early in summer, but seldom begin building until nearly the end of August.

Water quality and beavers

Beaver ponds, and the wetlands that succeed them, remove sediments and pollutants from waterways, including total suspended solids, total nitrogen, phosphates, carbon and silicates.

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 many animals and birds carry this parasite, and the major source of water contamination is by other humans. Norway has many beaver but has not historically had giardia and New Zealand has giardia but no beaver. 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.

Urban beavers

After 200 years, a beaver has returned to New York City
New 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...

, 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 were trapped to near extirpation and hadn't been seen in New York City since the early 1800s. The return of "Jose", named after Representative Jose Serrano
José Serrano
José Enrique Serrano is the U.S. Representative for , serving since 1990. He is a member of the Democratic Party....

 from the Bronx, is seen as evidence that efforts to restore the river have been successful. "Jose Serrano" has been sighted below the East Tremont bridge at Drew Gardens as recently as June 2009.
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 installing a pipe 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, led to the return of steelhead trout and river otter
River otter
River otter may refer to:*River Otter, a river in Devon*European Otter*Japanese River Otter*Neotropical River Otter*North American River Otter, a common animal in North American waterways*Southern River Otter, found in Chile and Argentina...

 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 Aurora, Colorado
Aurora, Colorado
City of Aurora is a Home Rule Municipality spanning Arapahoe, Adams, and Douglas counties in Colorado. Aurora is an eastern suburb of the Denver-Aurora-Broomfield, CO Metropolitan Statistical Area . The city is the third most populous city in the Colorado and the 56th most populous city in the...

, at the Star-K Ranch Park, two active beaver dams and one inactive beaver dam may be seen, with a beaver burrow in the north banks of the Sand Creek along the active beaver pond

As an introduced non-native species

In the 1940s, beavers were brought to the island of Tierra Del Fuego
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...

.

Family life

The basic social units of beaver social organization are families consisting of an adult male and adult female in a monogamous pair and their kits and yearlings. Beaver families can have as many as ten members in addition to the monogamous pair. Groups this size or close to this size build more lodges to live in while smaller families usually need only one. However, large families in the northern hemisphere have been recorded living in one lodge. Beaver pairs mate for life; however, if a beaver's mate dies, it will partner with another one. Extra-pair copulations also occur. In addition to being monogamous, both the male and female take part in raising offspring. They also both mark and defend the territory and build and repair the dam and lodge. When young are born, they spend their first month in the lodge and their mother is the primary caretaker while their father maintains the territory. In the time after they leave the lodge for the first time, yearlings will help their parents build food caches in the fall and repair dams and lodges. Still, adults do the majority of the work and young beavers help their parents for reasons based on natural selection rather than kin selection. They are dependent on them for food and for learning life skills. Young beavers spend most of their time playing but also copy their parents' behavior. However while copying behavior helps imprint life skills in young beavers it is not necessarily immediately beneficial for parents as the young beaver do not perform the tasks as well as the parents.

Older offspring, which are around two years old, may also live in families and help their parents. In addition to helping build food caches and repairing the dam, two-year olds will also help in feeding, grooming and guarding younger offspring. While these helping two-year olds helps increase chance of survival for younger offspring, they are not essential for the family and two-year olds only stay and help their families if there is a shortage of resources in times of food shortage, high population density, or drought. When beavers leave their natal territories, they usually do not settle far. Beavers can recognize their kin by detecting differences in anal gland secretion composition using their keen sense of smell. Related beavers share more features in their anal gland secretion profile than unrelated beavers. Being able to recognize kin is important for beaver social behavior and it causes more tolerant behavior among neighboring beavers.

Territories and spacing

Beavers maintain and defend territories, which are areas for feeding, nesting and mating. They invest much energy in their territories, building their dams and becoming familiar with the area. Beavers mark their territories by constructing scent mounts made of mud, debris and castoreum, a urine based substance excreted though the beavers castor sacs between the pelvis and base of the tail. These scent mounts are established on the border of the territory. Once a beaver detects another scent in its territory, finding the intruder takes priority, even over food.
Because they invest so much energy in their territories, beavers are intolerant of intruders and the holder of the territory is more likely to escalate an aggressive encounter. These encounters are often violent. In order to avoid such situations, a beaver marks its territory with as many scent mounds as possible, signaling to intruders that the territory holder has enough energy to maintain its territory and thus able to put up a good defense. As such, territories with more scent mounts are avoided more often than ones with fewer mounts. Scent marking increases in August during the dispersal of yearlings, in an attempt to prevent them from intruding on territories. Beaver also exhibit a behavior known as the "Dear Enemy Phenomenon". A territory holding beaver will investigate and become familiar with the scents of its neighbors. As such they respond less aggressively to intrusions by their territorial neighbours than those made by nonterritorial floaters or "strangers".

Commercial uses

Both beaver testicles and 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...

, a bitter-tasting secretion with a slightly fetid odor contained in the castor sacs of male or female beaver, have been articles of trade for use in traditional medicine. Yupik (Eskimo
Eskimo
Eskimos or Inuit–Yupik peoples are indigenous peoples who have traditionally inhabited the circumpolar region from eastern Siberia , across Alaska , Canada, and Greenland....

) medicine used dried beaver testicles like willow bark to relieve pain. Dried beaver testicles were also used as effective contraception. Beaver testicles were exported from Levant
Levant
The Levant or ) is the geographic region and culture zone of the "eastern Mediterranean littoral between Anatolia and Egypt" . The Levant includes most of modern Lebanon, Syria, Jordan, Israel, the Palestinian territories, and sometimes parts of Turkey and Iraq, and corresponds roughly to the...

 (a region centered on Lebanon
Lebanon
Lebanon , officially the Republic of LebanonRepublic of Lebanon is the most common term used by Lebanese government agencies. The term Lebanese Republic, a literal translation of the official Arabic and French names that is not used in today's world. Arabic is the most common language spoken among...

 and Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

) from the tenth to nineteenth century. Claudius Aelianus
Claudius Aelianus
Claudius Aelianus , often seen as just Aelian, born at Praeneste, was a Roman author and teacher of rhetoric who flourished under Septimius Severus and probably outlived Elagabalus, who died in 222...

 comically described beavers chewing off their testicles to preserve themselves from hunters, which is not possible because the beaver's testicles are inside its body. European beavers (Castor fiber) were eventually hunted nearly to extinction in part for the production of castoreum, which was used as an analgesic
Analgesic
An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....

, anti-inflammatory
Anti-inflammatory
Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....

, and antipyretic
Antipyretic
Antipyretics ; an-tee-pahy-ret-iks; from the Greek anti, against, and pyreticus, are drugs or herbs that reduce fever. Normally, they will not lower body temperature if one does not have a fever. Antipyretics cause the hypothalamus to override an interleukin-induced increase in temperature...

. Castoreum was described in the 1911 British Pharmaceutical Codex
British Pharmaceutical Codex
The British Pharmaceutical Codex was first published in 1907, to supplement the British Pharmacopoeia which although extensive, did not cover all the medicinal items that a pharmacist might require in daily work...

 for use in dysmenorrhea
Dysmenorrhea
Dysmenorrhea is a gynecological medical condition of pain during menstruation that interferes with daily activities, as defined by ACOG and others. Still, dysmenorrhea is often defined simply as menstrual pain, or at least menstrual pain that is excessive...

 and hysterical
Hysteria
Hysteria, in its colloquial use, describes unmanageable emotional excesses. People who are "hysterical" often lose self-control due to an overwhelming fear that may be caused by multiple events in one's past that involved some sort of severe conflict; the fear can be centered on a body part, or,...

 conditions (i.e. pertaining to the womb), for raising blood pressure
Blood pressure
Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...

 and increasing cardiac output
Cardiac output
Cardiac output is the volume of blood being pumped by the heart, in particular by a left or right ventricle in the time interval of one minute. CO may be measured in many ways, for example dm3/min...

. The activity of castoreum has been credited to the accumulation of salicin from willow trees in the beaver's diet, which is transformed to salicylic acid
Salicylic acid
Salicylic acid is a monohydroxybenzoic acid, a type of phenolic acid and a beta hydroxy acid. This colorless crystalline organic acid is widely used in organic synthesis and functions as a plant hormone. It is derived from the metabolism of salicin...

 and has an action very similar to aspirin. Castoreum continues to be used in perfume
Perfume
Perfume is a mixture of fragrant essential oils and/or aroma compounds, fixatives, and solvents used to give the human body, animals, objects, and living spaces "a pleasant scent"...

 production.

Much of the early European exploration and trade of Canada was based on the quest for beaver. The most valuable part of the beaver is its inner fur whose many minute barbs make it excellent for felt
Felt
Felt is a non-woven cloth that is produced by matting, condensing and pressing woollen fibres. While some types of felt are very soft, some are tough enough to form construction materials. Felt can be of any colour, and made into any shape or size....

ing, especially for hats. In Canada a 'made beaver' or castor gras that an Indian had worn or slept on was more valuable than a fresh skin since this tended to wear off the outer guard hairs.

Trapping

Beavers have been trapped for millennia, and this continues to this day. Beaver pelts were used for barter by 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...

 in the 17th century to gain European goods. They were then shipped back to Great Britain and France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 where they were made into clothing items. Widespread hunting and trapping of beavers led to their endangerment
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

. Eventually, 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...

 declined due to decreasing demand in Europe and the takeover of trapping grounds to support the growing agriculture sector. A small resurgence in beaver trapping has occurred in some areas where there is an over-population of beaver; trapping is done when the fur is of value, and the remainder of the animal may be used as feed. In the 1976/1977 season, 500,000 beaver pelts were harvested in North America.

In culture

In wider culture, the beaver is famed for its industriousness. The English verb "to beaver" means to work hard and constantly.

As a national emblem

The importance of the Beaver in the development of Canada through the fur trade led to its official designation as the national animal in 1975. The animal has long been associated with Canada, appearing on the coat of arms 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...

 in 1678. It is depicted on the Canadian five-cent piece
Nickel (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 pictorial postage stamp issued in the Canadian colonies
British North America
British North America is a historical term. It consisted of the colonies and territories of the British Empire in continental North America after the end of the American Revolutionary War and the recognition of American independence in 1783.At the start of the Revolutionary War in 1775 the British...

  in 1849 (the so-called "Three-Penny Beaver
Postage stamps and postal history of Canada
The postal history of Canada falls into four major periods: French control , British control , colonial government control , and the Dominion of Canada, since 1867.- Origins :...

"). As a national symbol, the beaver was chosen to be the mascot of the 1976 Summer Olympics
1976 Summer Olympics
The 1976 Summer Olympics, officially known as the Games of the XXI Olympiad, was an international multi-sport event celebrated in Montreal, Quebec, Canada, in 1976. Montreal was awarded the rights to the 1976 Games on May 12, 1970, at the 69th IOC Session in Amsterdam, over the bids of Moscow and...

 held in Montreal
Montreal
Montreal is a city in Canada. It is the largest city in the province of Quebec, the second-largest city in Canada and the seventh largest in North America...

 with the name "Amik" ("beaver" in Ojibwe
Ojibwe language
Ojibwe , also called Anishinaabemowin, is an indigenous language of the Algonquian language family. Ojibwe is characterized by a series of dialects that have local names and frequently local writing systems...

). The beaver is also the symbol of many units and organizations within the Canadian Forces
Canadian Forces
The Canadian Forces , officially the Canadian Armed Forces , are the unified armed forces of Canada, as constituted by the National Defence Act, which states: "The Canadian Forces are the armed forces of Her Majesty raised by Canada and consist of one Service called the Canadian Armed Forces."...

, such as on the cap badges of the Royal 22e Régiment
Royal 22e Régiment
The Royal 22nd Regiment is an infantry regiment and the most famous francophone organization of the Canadian Forces. The regiment comprises three Regular Force battalions, two Primary Reserve battalions, and a band, making it the largest regiment in the Canadian Army...

 and the Canadian Military Engineers
Canadian Military Engineers
The Canadian Military Engineers is the military engineer branch of the Canadian Forces.-Mission:The mission of the Canadian Military Engineers is to contribute to the survival, mobility, and combat effectiveness of the Canadian Forces...

. Toronto Police Services, London Police Service
London Police Service
The London Police Service provides policing services for the London, Ontario, Canada. Established in 1855 and renamed from the name London Police Force, its current headquarters is located at 601 Dundas Street in London, Ontario.-Organization:...

, Canadian Pacific Railway Police Service
Canadian Pacific Railway Police Service
The Canadian Pacific Police Service is a private police force enforcing safety and policing along Canadian Pacific Railway properties and rail lines in Canada and the United States, including limited sections of the Milton line of GO Transit in the Greater Toronto Area.The current head of the CP...

 and Canadian Pacific Railway
Canadian Pacific Railway
The Canadian Pacific Railway , formerly also known as CP Rail between 1968 and 1996, is a historic Canadian Class I railway founded in 1881 and now operated by Canadian Pacific Railway Limited, which began operations as legal owner in a corporate restructuring in 2001...

 crest bears the beaver on their crest or coat of arms.

Others who have used the beaver in their company or organizational symbol or as their mascot include:
  • Beaver Buzz
    Beaver Buzz
    Beaver Buzz is an energy drink line produced in Canada by DD Beverage Company of British Columbia, under the brand of Canadian Beaver Buzz Energy. The beverages include taurine, caffeine, Siberian Ginseng, Guarana seed extract and various vitamins, and use cane sugar instead of commonly-used high...

  • Roots Canada
  • Beaver Lumber
    Beaver Lumber
    Beaver Lumber was a Canadian building supply chain owned by Molson. It was once Canada's fourth largest building supply chain with 138 stores. In 2000 it was purchased by Home Hardware, a cooperative of over 1000 independent Canadian hardware stores...

  • The Beaver (magazine)
    The Beaver (magazine)
    Canada's History is the official magazine of Canada's National History Society. It is published six times a year, and aims to promote interest in and knowledge of Canadian history. Founded in 1920 as The Beaver by the Hudson's Bay Company , the magazine was acquired by the Society in 1994...

  • Canadian Pacific Railway
    Canadian Pacific Railway
    The Canadian Pacific Railway , formerly also known as CP Rail between 1968 and 1996, is a historic Canadian Class I railway founded in 1881 and now operated by Canadian Pacific Railway Limited, which began operations as legal owner in a corporate restructuring in 2001...

  • Bemidji State University
    Bemidji State University
    Bemidji State University is a public state university in Bemidji, Minnesota, USA, located on the shores of Lake Bemidji. It is a part of Minnesota State Colleges and Universities .-History:BSU was founded in 1919 as Bemidji State Normal School...

  • 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...

  • 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...

  • Harper Creek High School
    Harper Creek High School
    Harper Creek High School is a high school in the Harper Creek School District located just outside the city of Battle Creek, Michigan. In 2005, Harper Creek opened a new state-of-the-art high school...

     (Battle Creek, Michigan)
  • 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...

  • 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...

  • McMaster University
    McMaster University
    McMaster University is a public research university whose main campus is located in Hamilton, Ontario, Canada. The main campus is located on of land in the residential neighbourhood of Westdale, adjacent to Hamilton's Royal Botanical Gardens...

     Society of Off-Campus Students
  • Parks Canada
    Parks Canada
    Parks Canada , also known as the Parks Canada Agency , is an agency of the Government of Canada mandated to protect and present nationally significant natural and cultural heritage, and foster public understanding, appreciation, and enjoyment in ways that ensure their ecological and commemorative...

  • New York City
    New 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...

  • The State of New York
    New York
    New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

  • The State 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...

  • 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...

  • St Anne's College, Oxford
  • The 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...

  • 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...

     Engineering
  • Buena Vista University
    Buena Vista University
    Buena Vista University is a private 4-year college located in Storm Lake, Iowa. Founded in 1891 as Buena Vista College, it is affiliated with the Presbyterian Church. The university's campus is situated on the shores of Storm Lake, a natural lake...

  • Washington State Parks & Recreation Commission
  • 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....

  • Huron University College
    Huron University College
    Huron University College, referred to locally as Huron College is one of the affiliated colleges of the University of Western Ontario in London, Ontario....

  • F.C. Paços de Ferreira
  • Beverley
    Beverley
    Beverley is a market town, civil parish and the county town of the East Riding of Yorkshire, England, located between the River Hull and the Westwood. The town is noted for Beverley Minster and architecturally-significant religious buildings along New Walk and other areas, as well as the Beverley...

     Market Town, East Yorkshire, UK

In dietary law

In the 17th century, based on a question raised by the Bishop of Quebec
Roman Catholic Archdiocese of Quebec
The Archdiocese of Québec is the oldest Catholic see in the New World north of Mexico. The archdiocese was founded as the Apostolic Vicariate of New France in 1658 and was elevated to a Diocese in 1674 and an Archdiocese in 1819...

, the Roman Catholic Church
Roman Catholic Church
The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with over a billion members. Led by the Pope, it defines its mission as spreading the gospel of Jesus Christ, administering the sacraments and exercising charity...

 ruled that the beaver was a 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...

 (beaver flesh was a part of the indigenous peoples' diet, prior to the Europeans' arrival) for purposes of dietary law. Therefore, the general prohibition on the consumption of meat
Meat
Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...

 on Fridays during Lent
Lent
In the Christian tradition, Lent is the period of the liturgical year from Ash Wednesday to Easter. The traditional purpose of Lent is the preparation of the believer – through prayer, repentance, almsgiving and self-denial – for the annual commemoration during Holy Week of the Death and...

 did not apply to beaver meat. The legal basis for the decision probably rests with the Summa Theologica
Summa Theologica
The Summa Theologiæ is the best-known work of Thomas Aquinas , and although unfinished, "one of the classics of the history of philosophy and one of the most influential works of Western literature." It is intended as a manual for beginners in theology and a compendium of all of the main...

of Thomas Aquinas
Thomas Aquinas
Thomas Aquinas, O.P. , also Thomas of Aquin or Aquino, was an Italian Dominican priest of the Catholic Church, and an immensely influential philosopher and theologian in the tradition of scholasticism, known as Doctor Angelicus, Doctor Communis, or Doctor Universalis...

, which bases animal classification as much on habit as anatomy. This is similar to the Church's classification of the 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...

, another semi-aquatic rodent.

In computer science

In computability theory
Computability theory (computer science)
Computability is the ability to solve a problem in an effective manner. It is a key topic of the field of computability theory within mathematical logic and the theory of computation within computer science...

, a busy beaver
Busy beaver
In computability theory, a busy beaver is a Turing machine that attains the maximum "operational busyness" among all the Turing machines in a certain class...

(from the colloquial expression for "industrious person") is a Turing machine
Turing machine
A Turing machine is a theoretical device that manipulates symbols on a strip of tape according to a table of rules. Despite its simplicity, a Turing machine can be adapted to simulate the logic of any computer algorithm, and is particularly useful in explaining the functions of a CPU inside a...

that attains the maximum "operational busyness" (such as measured by the number of steps performed, or the number of nonblank symbols finally on the tape) among all the Turing machines in a certain class.

Further reading

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External links

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