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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. Genetic research has shown the
European and North American populations to be distinct species and that hybridization is unlikely.
Beavers are best known for their natural trait of building dams in rivers.
Species
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 are tending to spread to new
locations. The beaver became extinct in Britain in the sixteenth century, but there are proposals, and a great deal of interest,
in reintroducing the European Beaver to Scotland.
The American Beaver (C. canadensis) is the national animal of Canada and is depicted on the Canadian five-cent piece and coat of arms. However, in several areas of that country,
it is considered a pest animal. It is also the state animal of Oregon, and a common
school emblem for engineering schools, including the California Institute of Technology and the Massachusetts Institute of
Technology.
Dams
The dams are created both as a protection against predators 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.
Destroying a beaver dam without removing the beavers takes a lot of effort.
Beaver, the largest European aquatic representative of the mammalian order RODENTIA, easily recognized by its
large trowel-like, scaly tail, which is expanded in the horizontal direction.
The word is descended from the Aryan name of the animal, cf. Sanskrit babhru's, brown, the great ichneumon, Lat.
fiber, Ger. Biber, Swed. bäver, Russ. bobr'; the root bhru has given
“brown,” and, through Romanic, “ bronze” and “ burnish.”
The true beaver (Castor fiber) is a native of Europe and northern Asia, but it is represented in North America by a
closely-allied species (C. canadensis), chiefly distinguished by the form of the nasal bones of the skull.
Beavers are nearly allied to the squirrels (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 habits 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 the habits are
aquatic.
Beavers have webbed hind-feet, and the claw of the second hind-toe double.
In length beavers—- European and American—- measure about 2 ft. exclusive of the tail, which is about 10 inches
long. They are covered with a fur to which they owe their chief commercial value; this consists of two kinds of hair—the
one close-set, silky and of a greyish colour, the other much coarser and longer, and of a reddish brown.
Beavers are essentially aquatic in their habits, never travelling by land unless driven by necessity. Formerly common in
England, the European beaver has not only been exterminated there, but likewise in most of the countries of the continent,
although a few remain on the Elbe, the Rhone and in parts of Scandinavia. The American species is also greatly diminished in numbers from incessant
pursuit for the sake of its valuable fur.
Beavers are sociable animals, living in streams, where, so as to render the water of sufficient depth, they build dams of mud
and of the stems and boughs of trees felled by their powerful incisor teeth. In the neighbourhood they make their
“lodges,” which are roomy chambers, with the entrance beneath the water. The mud is plastered down by the fore-feet,
and not, as often supposed, by the tail, which is employed solely as a rudder.
They are mainly nocturnal, and subsist chiefly on bark and twigs or the roots of water plants.
Beaver dam.
The dam differs in shape according to the nature of particular localities. Where the water has little motion it is almost
straight; where the current is considerable it is curved, with its convexity towards the stream. The materials made use of are
driftwood, green willows, birch and poplars; also mud and stones intermixed in such a manner as contributes to the strength
of the dam; but there is no particular method observed, except that the work is carried on with a regular sweep, and that all the
parts are made of equal strength.
“In places,” writes Hearne, “which have been long frequented by beavers undisturbed, their dams, by frequent
repairing, become a solid bank, capable of resisting a great force both of ice and water; and as the willow, poplar and birch
generally take root and shoot up, they by degrees form a kind of regular planted hedge, which I have seen in some places so tall
that birds have built their nests among the branches.”
Their houses are formed of the same materials as the dams, with little order or regularity of structure, and seldom contain
more than four old, and six or eight young beavers. It not unfrequently happens that 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 have
usually no communication with each other except by water.
The beavers carry the mud and stones with their fore-paws and the timber between their teeth. They always work in the night
and with great expedition. They cover their houses late every autumn with fresh mud, which, freezing when the frost sets in,
becomes almost as hard as stone, so that neither wolves nor wolverines can disturb their repose.
The favourite food of the American beaver 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, poplar and willow trees; but during the summer a more varied herbage, with the addition of berries, is consumed.
When the ice breaks up in spring they always leave their embankments, and rove about until a little before the fall of the
leaf, when they return to their old habitations, and lay in their winter stock of wood. They seldom begin to repair the houses
till the frost sets in, and never finish the outer coating till the cold becomes severe. When they erect a new habitation they
fell the wood early in summer, but seldom begin building till towards the end of August.
Castoreum is a substance contained in two pear-shaped pouches situated near the organs of reproduction, of a bitter taste and
slightly foetid odour, at one time largely employed as a medicine, but now used only in perfumery.
Fossil remains of beavers are found in the peat and other superficial deposits of England and the continent of Europe; while
in the Pleistocene formations of England and Siberia occur remains of a giant
extinct beaver, Trogontzerium cuvieri, representing a genus by itself.
Reference
External links
Geographic names
Beaver is also the name of several places in the United
States of America:
- Beaver, Pennsylvania
- Beaver, West Virginia
- Beaver, Wisconsin
- Beaver Township, Michigan
- Beaver Township, Minnesota
- Beaver Township, Pennsylvania
There is also Beavercreek, Ohio (a place, not to be
confused with the creeks/rivers listed below).
Beaver is also the name of several creeks and rivers throughout North America:
- Beaver Lumber, a former
lumber-housing product which in the mid-1990s replaced by mostly the Home Depot.
Other Uses of the term
Beaver also has a sexual slang meaning.
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