Blue whale feeding. Artwork sequence showing how a baleen whale such as this blue whale (Balaenoptera musculus) feeds. Baleen whales feed on small crustaceans, such as krill (yellow). They engulf them with their mouth, which do not contain teeth but have plates of baleen used to filter the krill out of the water, as shown in the final artwork (bottom). The second artwork in the sequence (upper centre) shows the suction created by the whale's mouth opening (arrows), drawing in the krill. Whales dive to feed, coming to the surface for air. The blue whale is the world's largest animal and can reach lengths of 27 metres and weigh 120 tonnes.