Beavers are semi-aquatic rodents native to North America and Europe. They are the only members of the family Castoridae, which contains a single genus, Castor. more...
Genetic research has shown the European and North American beaver populations to be distinct species and that hybridization is unlikely.
Beavers are best known for their natural trait of building dams in rivers and streams, and building lodges in the eventual artificial pond. They are the second largest rodents, after the capybara. Adult specimens weighing over 25kg are not uncommon.
The European Beaver (Castor fiber) was hunted almost to extinction in Europe, both for fur, and for castoreum, a secretion of its scent gland believed to have medicinal properties. However, the beaver is now being re-introduced throughout Europe. Several thousands live on the Elbe, the Rhone and in parts of Scandinavia. They have been reintroduced in Bavaria and The Netherlands and are tending to spread to new locations. The beaver finally became extinct in Great Britain in the sixteenth century: Giraldus Cambrensis 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 first-hand.
In October 2005, six European beavers were re-introduced to Britain in Lower Mill Estate in Gloucestershire, and there are plans for re-introductions in Scotland and Wales.
The American Beaver (C. canadensis) is the national animal of Canada; in fact, it is depicted on the Canadian five-cent piece and was on the first Canadian postage stamp, the Three Penny Beaver. However, in several areas of that country, it is considered a pest. It is also the state animal of Oregon, the state mammal of New York (after the historical emblem of New Netherland) and the mascot of Oregon State University. It is also a common school emblem for engineering schools, including the California Institute of Technology and the Massachusetts Institute of Technology. It is also an emblem for London School of Economics and the name of its student newspaper - The Beaver.
The extinct North American Giant beaver (Castoroides ohioensis) was one of largest rodents that ever evolved. It disappeared, with other large mammals in the Holocene extinction event, about 10,000 years ago.
The dams are created both as a protection against predators (bear is the only natural predator) and to provide easy access to food during winter. It is the sound of water in motion that stimulates the beavers to build, and if for example a pipe is placed under the dam to drain it the beavers will not do anything about it. However they repair any damage to the dam and build it higher as long as the sound is there. Conversely, beavers will attempt to build dams in response to recordings of water flowing even in the absence of water.
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