Beavers groom frequently, both in the lodge and on land, to remove debris from the coat and to waterproof it with oil from anal glands. When the animal emerges from the water to groom, it may start with its face and head, or with its belly. It begins by raking the fur with its fingernails, and then gets some difficult to reach spots with its hind feet. The two inner toes on each hind foot are modified for grooming. The innermost toe nail opens and closes over the toe, like a bird’s beak, and functions like a coarse toothed comb. The second toe has a “split nail” or “double nail”. The former term is more commonly used but the latter term is, perhaps, more accurate. It really is a double nail: It has a true nail and an additional horny growth between the true nail and the toe. The additional horny growth has a finely serrated upper edge which serves as a fine toothed comb.

Watch the video below and notice the use of both front and hind feet for grooming. The sounds at the beginning – the breathing, gnawing, and whimpering – are coming from another beaver near the camera but out of view.

It is sometimes said the beaver begins the grooming process by using its front paws to get oily secretion from its anal glands that it then rubs it into the fur with its feet to waterproof the coat. However, in all of my video clips of grooming beavers, the animal starts right in with combing its face or belly, without ever touching its cloaca. It appears the mere combing is more frequent than oil application.

Beavers also engage in social grooming, usually inside they lodge. A beaver’s body is so round and its limbs so short that it cannot groom its own back, so it relies on family members for that. Mutual grooming has an obvious health benefit, but it also reinforces family bonds.

Sources

Bailey, V. “The Combing Claws of the Beaver.” Journal of Mammalogy. 4 (1923): 77-709