Beaver - large rodents. Their body is massive, the tail is flattened from top to bottom and covered with large horny shields. The toes of the hind legs are connected by a swimming membrane, and the front ones are free. The claw of the second toe of the hind limbs is bifurcated, forming a peculiar fork, which, apparently, helps the beaver to comb the hair and remove the ectoparasites. The auricles are immersed when the animal is immersed in water, the nostrils are closed. Genital teeth 16: 4 in the upper and lower jaw. Beaver are common in Europe, Asia and North America. In this family, only one genus is distinguished, in which two species are distinguished.The beaver (Castor fiber) is well known to many. The body length reaches 1 m, weight 30 kg.