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 preceded the evolution of gigantic body size, indicating the evolution of novel feeding mechanisms did not cause the evolution of gigantism. The creation of the Antarctic circumpolar current and its effects on global climate patterns is excluded as being causal for the same reason. Gigantism also was preceded by divergence of different mysticete lineages, meaning multiple lineages arrived at large size independently. It is possible the Plio-Pleistocene increase in seasonally intense upwellings causing high-prey-density zones led to gigantism. When swimming, baleen whales rely on their flippers for locomotion in a wing-like manner similar to penguins and sea turtles. Flipper movement