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 (e.g. minke whales) also prey on schools of fish. Skim-feeders, like bowhead whales, feed upon primarily smaller plankton such as copepods. They feed alone or in small groups. Baleen whales get the water they need from their food, and their kidneys excrete excess salt. The lunge-feeders are the rorquals. To feed, lunge-feeders expand the volume of their jaw to a volume bigger than the original volume of the whale itself; to do this, the mouth inflates to expand the mouth. The inflation of the mouth causes the throat pleats to expand, increasing the amount of water that the mouth can