This is the biggest rodent in Russian fauna. It has a chunky body 74-120 cm in length; the weight of the animal is about 20 kilos. The coloration is brown but it’s changeable from light-brown to dark-brown. The thick fur consists of coarse hair and soft down hair. The flat and wide tail is covered by horny scales. There are paddles between hind feet fingers. It is very good diver and swimmer and is capable of gnawing wood under water.

The beaver feeds on leaves and young tree or shrub sprouts in the summer and on bark, woody forage and plant roots – in the winter. The favorite food is willow, birch, alder and aspen. The animal willingly eats bark of fir, pine and cedar. It cuts and builds up a stock of 100-130 small trees and shrubs 6 cm thick for the coming winter.
Before the XVII century the beavers inhabited all the convenient landscapes of Siberia but they were exterminated by the end of the XIX century. The reacclimatization of beavers started in 1948 by letting the animals free at the Big Kemchug River; the experiment was successful.

The beaver is active at night and in twilight. It prefers sullen forest rivers with dead lakes and steep shores. The animal frequently settles at small creeks by blocking them with dams made of wood, sward and river mud. The beavers dig sophisticated burrows in steep river shores with entrances located under water. If there are flat shores or shallow waters the animal builds lodges out of wood and mud; such lodges have underwater entrances and large living space above water. The beaver is capable of gnawing and cutting a tree up to 1 meter thick. It gnaws trunks and big branches in pieces and moves them toward its lodge. In order to float the wood the beaver digs special channels. During winter it leads a subglacial way of life and goes up to the surface very rarely.

At this time the beaver feeds on its stocks of woody forage. The coupling period lasts from the end of the winter till the middle of the spring. The gestation lasts 105 days. The newborn cubs are covered with fur; the can see and have body length of 25 cm and average weight of 500 grams. The young beavers are capable of swimming in 1-2 days after birth. They feed on mother’s milk for two months though in three weeks they can already eat vegetable food. The male beavers do not participate in youngsters’ nurturing – they leave the family lodge for this period. The beavers’ lifespan is quite lengthy (up to 35 years in captivity).

The main enemies are bear, wolverine and stray dogs.