The mouths of whales filter krill for food via sheets of feathered horn, or baleen.


“One group of whales has specialised in feeding on tiny shrimp-like crustaceans, krill, which swarm in vast clouds in the sea. Just as teeth are of no value to mammals feeding on ants, so they are no use to those eating krill. So these whales, like ant-eaters, have lost their teeth. Instead they have baleen, sheets of horn, feathered at the edges, that hang down like stiff, parallel curtains from the roof of the mouth. The whale takes a huge mouthful of water in the middle of the shoal of krill, half-shuts its jaws and then expels the water by pressing its tongue forward so that the krill remains and can be swallowed. Sometimes it gathers the krill by slowly cruising where it is thickest. It also can concentrate a dispersed shoal by diving beneath it and then spiralling up, expelling bubbles as it goes, so that the krill is driven towards the centre of the spiral. Then the whale itself, jaws pointing upwards, rises in the centre and gathers them in one gulp.” (Attenborough 1979:242)

Life on Earth: A Natural HistoryMarch 1, 1970
David Attenborough

Blue WhaleBalaenoptera musculusSpecies