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North American beaver

Castor d'Amérique

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North American beaver

Facts about the North American beaver

  • Weighing between 11 and 35 kg, the American Beaver is the largest rodent in North America, the second largest among the 1,500 species of all the world’s rodents.
  • Total length including the tail: between 87,5 cm and 127 cm.
  • The broad, flat, scaly tail is used both as a fin and a paddle. To signal danger, the beaver will strike the surface of the water with its tail. The sound can be heard as far as a kilometer away.
  • The hindfeet are webbed and have 5 long toes with claws. Two of these claws, one on each hindfoot, are split; the beaver uses them like a comb to dress its fur.
  • The small forefeet are not webbed. Capable of performing with almost the same skill and precision as human hands, the beaver puts them to good use in its building activities.
  • Long, narrow and orange-coloured, the incisors are very sharp and never stop growing.
  • The beaver constantly grooms its thick pelage. The fur is waterproof and protects the beaver in cold air and freezing water.
  • The beaver can swim as fast as 7 km/h and stay immersed for up to 15 minutes. When the beaver is underwater, its ears and nostrils close and a clear membrane covers its eyes.
  • A beaver can even eat underwater without choking.


Castor d'AmériqueThe beaver makes its home in tree-edged ponds, swamps and lakes. Its impressive engineering skills come in handy for building its dwelling which it makes out of branches, tree trunks and mud. A beaver lodge can be up to 3 m high and 7 m in diameter.

The entrances to the lodge are submerged and can only be reached by diving underwater. This protects the beaver’s home from predators. The dam helps control the water level so it will reach the entrances without flooding the lodge.  Made mostly of logs, the dam is reinforced with stones, vegetation and mud. The dam can measure up to 45 meters long, 2 meters high and 3 meters wide.


Castor d'AmériqueThere are only two species of beavers in the world. The American Beaver (Castor canadensis) is found in great numbers throughout Alaska, Canada and the United States. The European Beaver (Castor fiber) population, ranging from France to Russia, is considerably smaller.


The beaver cuts down large trees by chewing in a circle around the base of the trunk. It then chops up the trunk into smaller pieces so they are easier to carry. Beavers are partial to trees such as poplar, willow, white birch and alder. A single beaver can cut down more than 200 trees a year. 


Castor d'AmériqueThe beaver is an herbivore and eats mostly bark (some 500 grams a day). Its diet varies from season to season and also includes branches, leaves, roots and aquatic vegetation.





The birth of the young occurs in the spring. Gestation lasts 15 weeks. There are usually three or four kits to a litter which the female nurses until they are 6 to 10 weeks old. The newborn kits measure 12 cm long and weigh 450 g. The kits learn how to swim only hours after they’re born. But they will have to gain a little weight before they are able to dive because their thick fur keeps them afloat just like a lifejacket. The young remain under their parents’ protection for several months.

Beavers live in family groups, which consist of the parents, the newborn and other offspring that are less than two years old.  


Beaver dams promote the growth of vegetation and also create a reservoir to ensure a sufficient supply of water in case of drought. Through their dam building, not only do beavers transform their surroundings, they also contribute to ecological diversity. Fish, birds and a variety of deer benefit from an increase in available food and water.

By summer’s end, when the beavers have made the most of the resources near at hand, the beaver family sets about making the dam bigger. By increasing the size of the body of water where they live, they gain access to new food sources without fear for their safety. The beaver is active mainly at night. Each family determines its territory by spraying it with castoreum, which is a thick, strong-smelling liquid secreted in glands located beneath a beaver’s tail.


This is the season when the beaver will consume as much bark as possible to fatten up before winter. It must also reinforce all that it has built before the frost and cold set in. A thick layer of mud and branches is added to better insulate the lodge. Reserves of wood are collected and piled underwater around the lodge. The water is now so cold it will prevent the wood from rotting and preserve its nutritional value. The winter frosts harden the lodge, and also help keep predators such as wolves from getting inside.

The young beavers leave the family group when they’re about 2 years old to start a family of their own. Life expectancy for a beaver is 10 years, but some can live up to the age of 24. 


Beavers spend most of the winter inside their lodge. Even in extreme cold, the heat from the beavers’ bodies will ensure the temperature within always remains above freezing.

The food reserves stockpiled during the previous months will now ensure their survival. About 300 trees are needed to adequately feed a beaver family in winter. When the ice sets in on the waterways, all the beaver has to do is dive down to its storage area. In the case of extreme cold, the beaver can always make it through the winter by eating the wood its lodge is made with. February is the mating season.

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