Natural history of beaver

distinctive feature is the beaver's large orange incisors which it uses for gnawing wood. Cheek flaps can close behind these teeth, allowing the beaver to chew underwater. Its webbed hind-feet are much larger than the forepaws, which have specialized claws for digging. The beaver is a graceful swimmer, usually moving slowly, but it will move up to 2 metres per second underwater if cornered. On land a beaver will gallop if startled, but is clumsy. They are occasionally killed by falling trees.

Beaver are highly social animals, living in family groups. They are monogamous. A litter of two to six kits is born in spring. A family group also includes the previous year's offspring. At two years of age beaver leave the lodge in search of a mate and new territory. This is normally the only time beaver move long distances overland, unless a family exhausts it food supply and must establish a new home range.

Beaver feed on woody plants, consuming leaves, bark, buds, sap, roots and fruits. In winter when its food is restricted to an underwater cache, the diet may be restricted to bark. The beaver's digestion is enhanced by special stomach glands, but its unusual diet depends mostly on adaptation for gathering and consuming large quantities of the most nutritious fibrous material. Its preferred foods are Salix (willow) and Populus (aspen), though Acer (maple), Ulnus (alder) and other woody species are consumed.

When a beaver cuts down a tree it makes two cuts in the trunk, one above the other, then tears off the piece of wood between the cuts. It usually works its way around the trunk until the tree breaks. The beaver usually runs into the water while the tree falls, then listens to make sure the noise has attracted no predators before re-emerging. The beaver removes the branches then rolls the trunk into the river. Some of the wood may be stored in deep water, while other pieces are used for construction of a dam or lodge.

Dams are built to make the river deep enough for the beaver to move about safely and store food. They are constructed of logs, sticks and rocks plastered together with mud. The lodge may be built in the middle of the stream or on the edge, with several underwater entrances leading to a dry chamber 10 to 15 cm above water level, where the animals can stay warm and dry in winter. Sometimes instead of a lodge a family may build a burrow in the riverbank. Beavers that live in lakes usually do not build dams.

Beaver inhabiting the Eramosa

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