Baleen Baleen Baleen is a filter-feeder system inside the mouths of baleen whales. The baleen system works by a whale opening its mouth underwater and taking in water. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food source for the whale. Baleen is similar to bristles and consists of keratin, the same substance found in human fingernails and hair. Baleen is a skin derivative. Some whales, such as the bowhead whale, have longer baleen than others. Other whales, such as the gray whale, only use one side of their
Baleen whale top of their head, stretching from the tip of the rostrum to the blowhole, and, in right whales, on the chin. Like other marine mammals, they lack sebaceous and sweat glands. The baleen of baleen whales are keratinous plates. They are made of a calcified, hard α-keratin material, a fiber-reinforced structure made of intermediate filaments (proteins). The degree of calcification varies between species, with the sei whale having 14.5% hydroxyapatite, a mineral that coats teeth and bones, whereas minke whales have 1–4% hydroxyapatite. In most mammals, keratin structures, such as wool, air-dry, but aquatic whales rely on calcium salts to