Beaver

Why do beavers build dams?

The beavers of North America build a dam to create an artificial lake in which to construct an island home or lodge. Often the beavers work in colonies.  After choosing a narrow place in a shallow stream with a firm bottom, they set to work felling trees by standing on their hind legs and gnawing round the trunks with their largef chisel-like teeth. When the tree is down, the beavers lop off the branches and cut the trunk into suitable lengths which they drag into the stream and sink across the current. Sticks, stones and mud are used to keep the dam in position and mare it watertight.

In the middle of the lake thus created the beavers use the same materials to build their lodge. When completed this is dome-shaped, ventilated structure about 8 feet in diameter and rising well clear of the surface of the lake. There are two entrances, both under water. One of these is used for general purposes, the other as an escape route in an emergency or for bringing in food.

The lodge serves as a home, a nursery for the baby beavers and a storehouse for food in winter.  The beavers feed chiefly on the bark of trees, of which they keep a plentiful supply at the bottom of the dam, on the bed of the lake and built into the fabric of their home.

In winter, when the lake is frozen over and snow covers the ground, the lodge is virtually an impregnable fortress which the beavers can leave and enter by swimming under the ice. Beavers are experts at keeping the water fin the lake at the rightf level by constructing canals. They work industriously to maintain both dam and lodge - hence the origin of that popular phrase about being "as busy as a beaver".