Page 26 - Present Day Wildlife_Float

Beavers (Order: Rodentia) are large semi-aquatic rodents found in the Genus: Castor, in the
Family Castoridae. There are two extant species, the North American (Castor canadensis). They are
found across the United States, Canada, southern Alaska, and some parts of northern Mexico, and the
Eurasian beaver (Castor fiber), found across Western, Southern, Central and Eastern Europe, Scandi-
navia, Russia through China and Mongolia. The Eurasian beaver is the longer of the two species with a
body length of 80 to 100 cm and weighs around 11 to 30 kg, while the American beaver has a body
length of only 74 to 90 cm, but its body weight is around 11 to 32 kg which can increase in old age to
around 50kg. The earliest Beaver fossils found so far, date back to over 8 to 10 million years ago

Beavers, although slow and rather cum-
bersome on land, are first class swimmers.
Their bodies are well adapted for their aquatic
lifestyle. Their nostrils and ears have special
valves that close when underwater and their
eyes are protected by a membrane that comes
down to protect them. The large hind feet have
webbed toes and the front feet are specially
adapted, with clawed toes that it can use to
dig, burrow and manipulate large logs with
ease. Its tongue can be used to block its mouth
creating a watertight seal, or if it wants to
work or feed while submerged it can close its
lips behind its incisors, keeping its mouth wa-
ter free, while allowing it to bite and gnaw at
wood or food.

Beavers like to live and swim in relative-
ly deep water and if there is none available they will dig canals and dam local streams or rivers with
logs creating a large artificial lake. Once the lake has formed they will often build a large dome shaped
island lodge of branches and mud where the family or group will live. However, where possible, bea-
vers like to burrow out river bank dens. These dens or lodges can be huge, reaching sizes of 5 metres
high and 12 metres wide and have several underwater entrances tunnelled along the river bank. The
floor of these huge chambers is covered with soft vegetation and can accommodate a very large family
or group.

Beavers are herbivores, consuming a variety of tree barks, leaves, aquatic plants, and grasses.
Unlike many other herbivores beavers do not hibernate over winter. Instead, as winter approaches
they store some fat at the base of their tail and store logs and twigs by attaching them to the river bed
near to the lodge entrance. Huddled together for warmth during winter the beaver simply retrieves its
stored food from the river bed and returns to the warmth of the den. They are rarely seen in the open
during the winter months.
Beaver Dams Because of their activities beavers are looked upon as a keystone

species. The ponds and canals they build create whole new ecosystems
favourable to many different species like water beetles, birds, bats, frogs,
and fish. The dams they construct often stop flooding further down-
stream, save water during droughts; and even filter the water that passes
through them. However, this favourable view is not shared by all; farmers
living near to beavers often find their land being flooded by the dams they
construct, and their crops decimated by the beavers themselves.

The beaver story, however, has not always been a positive one. In the
1900, across the globe the beaver populations, due to overhunting, had
dropped to critical. In the 1920, laws were passed in many countries, in an
attempt to save and protect the dwindling beaver populations. Today bea-
vers are not listed as an endangered species. They have even been suc-
cessfully reintroduced back into many countries and areas where they had
been totally wiped out. (See: Rodent)