American Beaver

The beaver (Castor canadensis) is an architect. Its complex creation of dams and lodges has earned it a reputation as one of nature's greatest engineers. A beaver gnaws its way round the trunk of a tree and can fell a sapling in under 30 minutes. Thus begins the dam, the beaver using its hand-like front paws to fill the gaps with mud, stones and vegetation. The lake formed behind the dam provides a safe retreat from predators, a storehouse for essential winter supplies of timber for food, and an underwater entrance to the family home.

The beaver and its extended family work together at night, posting a sentry that spanks the water with its tail to warn of danger. Closing its ears and nostrils, and lowering its heart rate, the beaver can stay submerged for up to 15 minutes.