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European Beaver

European Beaver

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Encyclopedia
The Eurasian beaver or European beaver (Castor fiber) is a species
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...

, which was once widespread in 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...

, where it was hunted to near extinction both for 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...

 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
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,...

 believed to have medicinal properties. Re-introduced through much of its former range, it now occurs from the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...

 to China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 and Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...

.

Physical characteristics


The fur colour of Eurasian beavers varies geographically. Light, chestnut-rust is the dominant colour in Belarus
Belarus
Belarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...

. In Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, the beavers of the Sozh River basin are predominantly blackish brown, while beavers in the Voronezh
Voronezh
Voronezh is a city in southwestern Russia, the administrative center of Voronezh Oblast. It is located on both sides of the Voronezh River, away from where it flows into the Don. It is an operating center of the Southeastern Railway , as well as the center of the Don Highway...

 Reserve are equally distributed between brown and blackish-brown.

Eurasian beavers on average weigh 18 kg, the largest specimen on record having weighed 31.7 kg.

Differences from North American beaver


Although superficially similar to the North American beaver, there are several important differences. Eurasian beavers tend to have less rounded heads, longer, narrower muzzles, thinner, shorter, and lighter underfur, narrower, less oval-shaped tails, and have shorter shin bones, making them less capable of bipedal locomotion than the North American species. Eurasian beavers have longer nasal bones than their 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, one fifth 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 Eurasian resulting in one stillborn kit. These factors make interspecific breeding unlikely in areas where the two species' ranges overlap.

Reproduction


Eurasian 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 107 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.

Range


The Eurasian (or European) beaver is recovering from near extinction, after depredation by humans for its fur and castoreum decimated populations to an estimated 1,200 by the early 20th century. In many European nations, the beaver went extinct but reintroduction and protection has led to gradual recovery to approximately 639,000 individuals by 2003. Milishnikov found in genetic studies that beaver likely survived east of the Urals
Ural Mountains
The Ural Mountains , or simply the Urals, are a mountain range that runs approximately from north to south through western Russia, from the coast of the Arctic Ocean to the Ural River and northwestern Kazakhstan. Their eastern side is usually considered the natural boundary between Europe and Asia...

 from a nineteenth century population as low of 300 animals, and that factors contributing to their survival include their ability to maintain sufficient genetic diversity to recover from a population as low as 3 individuals, and that beavers are monogamous and select mates that are genetically different from themselves. 83% of Eurasian beavers live in the former Soviet Union thanks to reintroductions, however the result is that beaver in Mongolia or Siberia do not appear significantly genetically different from samples from the European part of Russia, despite the great geographical distance.

Mainland Europe


In Romania
Romania
Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...

, beavers became extinct in 1824, being reintroduced in 1998, along the Olt River
Olt River
The Olt River is a river in Romania. It is the longest river flowing exclusively through Romania. Its source is in the Hăşmaş Mountains of the eastern Carpathian Mountains, near the village Bălan. It flows through the Romanian counties Harghita, Covasna, Braşov, Sibiu, Vâlcea and Olt...

, spreading to other rivers in Covasna County
Covasna County
Covasna is a county of Romania, in Transylvania, with the capital city at Sfântu Gheorghe.-Demographics:In 2002, it had a population of 222,449 and the population density was 60/km².*Hungarians – 73.79% *Romanians – 23.28%...

.

Beavers have been re-introduced in 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...

 and 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...

 and are tending to spread to new locations. After being reintroduced in the Biesbosch
Biesbosch
De Biesbosch , is one of the largest national parks of the Netherlands and one of the last freshwater tide areas in Europe. The Biesbosch consists of a rather large network of rivers and smaller and larger creeks with islands. The vegetation is mostly willow forests, although wet grasslands and...

 in 1988, the Dutch population has spread considerably (supported by additional reintroductions), and can now be found in the Biesbosch and surrounding areas, along the Meuse in Limburg
Limburg (Netherlands)
Limburg is the southernmost of the twelve provinces of the Netherlands. It is located in the southeastern part of the country and bordered by the province of Gelderland to the north, Germany to the east, Belgium to the south and part of the west, andthe Dutch province of North Brabant partly to...

, and in the Gelderse Poort and Oostvaardersplassen
Oostvaardersplassen
The Oostvaardersplassen is a nature reserve in the Netherlands, covering about . Despite having developed recently it already has international importance as a European wetland....

.

In Poland in May and June 2010 after major flooding, the Polish government and local authorities held beavers responsible for causing the flooding and demanded the culling of 150 beavers.

Scandinavia


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....

 the beaver had been hunted to extinction by around 1870. Between 1922 and 1939 approximately eighty individuals were imported from 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...

 and introduced to nineteen separate sites within the country.

Norwegian beavers also played an important role in reintroducing the locally extinct animal to Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

, but there the population also includes a substantial number of C. canadensis of Canadian origin. (The North American Beavers were imported to Finland in 1937, when it was not yet known that C. canadensis was a different species from the Eurasian beaver.)

In 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...

, the beaver was reintroduced to the wild in western 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...

 in 1999 and in Arresø
Arresø
Arresø is a lake located at , in the Hovedstaden region just north of Ølsted and east of Frederiksværk on the island of Zealand in Denmark.At 39.87 km² Arresø is Denmark's largest lake, based on area. The lake runs into Roskilde Fjord through the Arresø Canal in Frederiksværk...

, northern Zealand, in 2009 after it was hunted to extinction c. 1000 AD. The reintroduced beavers were caught in the river Elben in Germany. , the Danish population of beavers was estimated to be 100—120 individuals.

Great Britain



The beaver became extinct in Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

 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
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

 and in one river in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

, though his observations are clearly secondhand. The last reference to beavers in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 dates to 1526.

In 2001 the Kent Wildlife Trust
Kent Wildlife Trust
Kent Wildlife Trust covers the county of Kent, England, and is one of the largest of the 47 Wildlife Trust organisations in the United Kingdom, the Isle of Man and Alderney...

 with the Wildwood Trust
Wildwood Discovery Park
Wildwood Discovery Park is a woodland discovery park in north-east Kent, England. It features over fifty species of native British animals such as deer, badgers, wild boar and wolves...

 and Natural England
Natural England
Natural England is the non-departmental public body of the UK government responsible for ensuring that England's natural environment, including its land, flora and fauna, freshwater and marine environments, geology and soils, are protected and improved...

 imported two families of Eurasian beaver from Norway to manage a wetland nature reserve. This project pioneered the use of beaver as a wildlife conservation tool in the UK. The success of this project has provided the inspiration behind other projects 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....

 and Argyll
Argyll
Argyll , archaically Argyle , is a region of western Scotland corresponding with most of the part of ancient Dál Riata that was located on the island of Great Britain, and in a historical context can be used to mean the entire western coast between the Mull of Kintyre and Cape Wrath...

. The Kent beaver colony live in a 130 acre (0.5260918 km²) fenced enclosure at the wetland of Ham Fen. Subsequently the population of beaver has been supplemented in 2005 and 2008. The beaver continue to help restore the wetland by rehydrating the soils. Six Eurasian Beavers were released in 2005 into a fenced lakeside area 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 2007 a specially-selected group of four 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...

n beavers were released into a fenced enclosure in the 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:...

 nature reserve 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...

. It is hoped that the beavers will form a permanent colony, and the younger pair will be transferred to another location when the adults begin breeding again. The progress of the group will be followed as part of the BBC's Autumnwatch television series. A colony of beavers is established in a large enclosure at Bamff
Bamff
Bamff House is the home of the Ramsays of Bamff, and is located within a estate in Perthshire, Scotland. Bamff House began as a fortified tower in the late 16th Century and was added to and altered in almost every century since then. Bamff has been the home of several European beavers since 2002...

, Perthshire
Perthshire
Perthshire, officially the County of Perth , is a registration county in central Scotland. It extends from Strathmore in the east, to the Pass of Drumochter in the north, Rannoch Moor and Ben Lui in the west, and Aberfoyle in the south...

.

The first sustained and significant population of wild-living beavers in the United Kingdom became established on the Tay
River Tay
The River Tay is the longest river in Scotland and the seventh-longest in the United Kingdom. The Tay originates in western Scotland on the slopes of Ben Lui , then flows easterly across the Highlands, through Loch Dochhart, Loch Lubhair and Loch Tay, then continues east through Strathtay , in...

 watershed in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 as early as 2001 and has spread widely in the watershed, numbering from 20 to 100 individuals. Because these are likely escapees from any of several nearby sites with captive beavers, or were illegally released, they were targeted for removal by Scottish Natural Heritage
Scottish Natural Heritage
Scottish Natural Heritage is a Scottish public body. It is responsible for Scotland's natural heritage, especially its natural, genetic and scenic diversity. It advises the Scottish Government and acts as a government agent in the delivery of conservation designations, i.e...

 in late 2010. Proponents of the beavers argue that they have not been proven to be of "wrong" genetic stock and there is scientific evidence to support that they may represent a rather ideal mix of western European populations, since any single relict
Relict
A relict is a surviving remnant of a natural phenomenon.* In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas....

 population in western Europe is relatively genetically depauperate. The first of the wild Tayside beavers was trapped by Scottish Natural Heritage on the River Ericht
River Ericht
The River Ericht is a river in Perthshire, Scotland formed from the confluence of the rivers Blackwater and Ardle.It runs south for around 10 miles before discharging into the River Isla, and eventually the River Tay...

 in Blairgowrie
Blairgowrie and Rattray
Blairgowrie and Rattray and Raitear is possibly from an English language cognate of Gaelic ràth, meaning fortress + a Pictish term cognate with Welsh tref, meaning settlement) is a twin burgh in Perth and Kinross, Scotland. Amongst locals, the town is colloquially known simply as "Blair"...

, Perthshire
Perthshire
Perthshire, officially the County of Perth , is a registration county in central Scotland. It extends from Strathmore in the east, to the Pass of Drumochter in the north, Rannoch Moor and Ben Lui in the west, and Aberfoyle in the south...

 in early December 2010 and is being held in captivity in the Edinburgh Zoo
Edinburgh Zoo
Edinburgh Zoo, formally the Scottish National Zoological Park, is a non-profit zoological park located in Edinburgh, the capital city of Scotland...

. A Facebook group, Save the Free Beavers of the Tay, has nicknamed the captured wild beaver "Eric" and opposes the ongoing effort to trap Eric's relations.

In 2005, the Scottish Government turned down a licence application for unfenced reintroduction. However, in late 2007 a further application was made for a release project in 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....

, Argyll. This application was accepted, and the first beavers were released on the 29th May 2009. This initial release into the wild of 11 animals received a setback during the first year with the disappearance of two animals and the alleged illegal shooting of a third. This allegation was later refuted by Simon Jones of the Scottish Beaver Trial as there was no evidence to support the allegation and all three missing beavers were sighted after they left the release loch. However, the remaining population was increased in 2010 by further releases. In August 2010, at least two kits, estimated to be eight weeks old and belonging to different family groups, were seen in Knapdale Forest in Argyll.

The Scottish charity Trees for Life
Trees for Life (Scotland)
Trees for Life is a registered charity in Findhorn, Moray, formed in 1989 by Alan Watson Featherstone, as a direct result of the inspiration and example of Richard St. Barbe Baker, the 'Man of the Trees'...

 plans to reintroduce beavers in the Scottish Highlands
Scottish Highlands
The Highlands is an historic region of Scotland. The area is sometimes referred to as the "Scottish Highlands". It was culturally distinguishable from the Lowlands from the later Middle Ages into the modern period, when Lowland Scots replaced Scottish Gaelic throughout most of the Lowlands...

.

With the exception of the Knapdale and Tayside animals, all the beavers in the United Kingdom today are in semi-enclosed sites and not fully released into the wild. A 2009 report by Natural England
Natural England
Natural England is the non-departmental public body of the UK government responsible for ensuring that England's natural environment, including its land, flora and fauna, freshwater and marine environments, geology and soils, are protected and improved...

, the Government’s conservation body, and the People's Trust for Endangered Species recommended that beaver be reintroduced to the wild in England.

A study has been undertaken on the feasibility and desirability of a reintroduction of beavers to Wales by a partnership including the Wildlife Trusts, Countryside Council for Wales, Peoples Trust for Endangered Species, Environment Agency Wales, Wild Europe, Forestry Commission Wales, with additional funding from Welsh Power Ltd. The resulting reports are due to be published in 2010.

Ecology


Beaver are 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...

 helping support the ecosystem of which they are a part. They create wetlands which increase biodiversity and provide habitat for many rare species such as water voles, otters and water shrews. They coppice waterside trees and shrubs so that they re-grow as dense shrubs which provide cover for birds and other animals. Beaver dams trap sediment and improve water quality; recharge groundwater tables and increase cover and forage for trout and salmon. A recent study in Poland, found that beavers increased abundance and diversity of bats apparently because they create gaps in forest cover making it easier for bats to navigate in.

Beaver Impacts on Fish


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. 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. These findings are similar to several studies of beaver effects on fish in North America. Brook trout, coho and sockeye salmon 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...

. In addition, research in the Stillaguamish River basin in Washington state, found that extensive loss of beaver ponds resulted in an 89% reduction in coho salmon 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...

. 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 during periods of low stream flows, 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. A 2003 study showed that Atlantic salmon and Sea trout (S. trutta morpha trutta) spawning in the Numedalslågen River
Numedalslågen
-Location:Numedalslågen stretches for over 250 kilometres through the counties of Vestfold and Buskerud, beginning at the Hardangervidda plateau and meeting the ocean at Larvik in Vestfold. Numedalslågen is one of Norway's longest rivers. The rivers runs through the municipalities Larvik, Lardal,...

 and 51 of its tributaries in southeastern 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...

 were unhindered by beaver. In Norway, beaver dams are considered beneficial for Brown
Brown trout
The brown trout and the sea trout are fish of the same species....

 and Sea Trout populations (these are potamodromous and anadromous forms of the same species). There, beaver ponds produce increased food for young fish and provide refugia for large adults heading upstream to spawn.

Water Quality and Beaver


The misnomer ‘beaver fever’ was invented by the American press in the 1970s, after an outbreak of 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...

, was blamed on beavers. However, the outbreak area was also frequented by humans, who are generally the primary source of contamination of waters. In addition, many animals and birds carry this parasite. Giardiasis affects humans in southeastern Norway, but a recent study found no Giardia in the beavers there. 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. 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 but no beavers. In a 1995 paper recommending re-introduction of beaver to Great Britain, MacDonald stated that the only new diseases that beaver might convey to that country's birds and mammals in that country, are rabies and tularaemia - both diseases that should be preventable by statutory quarantine procedures and prophylactic treatment for tularaemia.

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.

See also

  • Scottish Beaver Trial
    • Knapdale in Argyll
      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....

  • River Tay
    River Tay
    The River Tay is the longest river in Scotland and the seventh-longest in the United Kingdom. The Tay originates in western Scotland on the slopes of Ben Lui , then flows easterly across the Highlands, through Loch Dochhart, Loch Lubhair and Loch Tay, then continues east through Strathtay , in...


External links