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 bone in the upper jaw beneath the eyes, and loose lower jaw bones at the chin. Baleen is believed to have evolved around 30 million years ago, possibly from a hard, gummy upper jaw, like the one a Dall's porpoise has; it closely resembles baleen at the microscopic level. The initial evolution and radiation of baleen plates is believed to have occurred during Early Oligocene when Antarctica broke off from Gondwana and the Antarctic Circumpolar Current was formed, increasing productivity of ocean environments. This occurred because the current kept warm ocean waters away from the area that is now Antarctica,