They have long claws and are used for digging, handling food and working on dams. The thumb is small and weak, but the little finger is strong and has taken over the thumb's role. The hind feet, broad and webbed between the toes, propel the animal through the water. A beaver's vision is weak, but its hearing and sense of smell are acute. Most food is located by smell.
Beavers are slow on dry land but quite mobile in the water.
Commercially, castoreum is used as an ingredient for some medicines and perfumes, not to mention trapping lures. Beavers have two other sacs, one on each side of the urogenital opening, which secrete an oil. The animal rubs this oil into its fur to repel water. Because its front teeth never stop growing, a beaver must continually cut wood to offset incisor growth. The upper and lower incisors are the primary cutters.