Natural history of beaver

On a February day with thick ice covering the Eramosa River, I cross to the far shore to look for a beaver lodge I located two months earlier. Deep snow fills the woods, but before long I find the familiar mound. In December I couldn't tell whether the lodge was occupied, but now several air holes reveal that at least one animal lives underneath. Its warm breath keeps the passages open.

There is no open water anywhere to be seen. The river is frozen solid for a hundred metres in either direction. Besides the air holes, nothing else gives a clue that anything lives here. These animals do not hibernate, but they are essentially trapped under snow and ice. If they relied on food along the shore they would starve. Fortunately, the industrious beaver has weighted wood to the bottom of the river using stones. This stash will provide enough bark for the family to live on throughout the winter. Meanwhile, winter's covering provides effective protection from hungry predators.

The beaver goes to great lengths to establish this elaborate home and food store. Its reputation for industry is well-deserved. The meaning of the creature's name in many Native languages is "little people." Next to humans, no other animal alters its habitat so drastically.

North American wetland habitats might have been much different if the beaver had become extinct, which it nearly did. Its population is estimated to have been 60 million, ranging across most of the continent, when Europeans arrived. Beaver fur is soft and shiny and wears well. It is also used to manufacture felt. The trade in beaver pelts became the single most important factor in the exploration and colonization of North America. Between 1700 and 1900 it was the most widely sought natural resource.

Beaver had been extirpated from most of its range in middle latitudes by the early 1900s, when the public started becoming concerned about the extinction of wildlife species. The beaver responded well to protection through regulated trapping. Live-trapping and restocking led to the species becoming successfully re-established through most of its former range.

It is the largest North American rodent, ranging up to 120 cm long (4 feet). Its most outstanding feature is the wide, scaly, hairless tail, flattened like a paddle, which it uses for propulsion underwater and for balance when standing upright on its hind legs. A beaver can walk bipedally, while clasping mud and sticks to its chest with its forefeet. The beaver also uses its tail to make a loud slap on the water's surface to warn other beavers of an intruder. Another