Beavers | Castoridae

Bevers | Castores

The heaviest rodent on the continent, and wholly fitted out for water. The tail is broad, flattened and covered with horny scales: a rudder in swimming, a prop when gnawing upright, a store of fat for the winter and, slapped down on the surface, an alarm for the whole family. The hind feet are large and webbed; one hind toe carries a split nail with which the fur is combed and kept waterproof with oil and castoreum. The underfur is extraordinarily dense and holds the skin dry. The incisors carry iron-bearing orange enamel on the front; the lips close behind them, so that wood can be gnawed under water without choking. They fell trees for bark and twigs, build dams and lodges, and dig canals to float the timber in. A monogamous pair keeps the previous year's young with it; the kits swim almost at once.