Baleen this issue. A whale's baleen plates play the most important role in its filter-feeding process. To feed, a baleen whale opens its mouth widely and scoops in dense shoals of prey (such as krill, copepods, small fish, and sometimes birds that happen to be near the shoals), together with large volumes of water. It then partly shuts its mouth and presses its tongue against its upper jaw, forcing the water to pass out sideways through the baleen, thus sieving out the prey, which it then swallows. People formerly used baleen (usually referred to as "whalebone") for making numerous items where
Baleen baleen. These baleen bristles are arranged in plates across the upper jaw of the whale. As a material for various human uses, baleen is usually called whalebone. It is not to be confused (but often is) with whale bone or whale's bone meaning the actual bones of whales, used in carving, for cutlery handles and other uses for the bones of various large species. Like other bone materials, this often functioned as a substitute for ivory. Depending on the species, a baleen plate can be long, and weigh up to . Its hairy fringes are called baleen hair or whalebone-hair.