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

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The baleen whale has specialized structures that enable it to efficiently consume small organisms, especially tiny shrimp-like crustaceans called krill.  Krill swarm in huge clouds in the ocean, where baleen whales scoop them up, water and all, and send them through a baleen filter-feeding system.

Mostly made of keratin—the same substance found in human fingernails and hair—baleen is similar to the bristles on a brush. It lines the whale’s upper jaw in plate-like structures with fringy tips. In baleen whales, these structures replace the bony teeth that are found in toothed whales. When a baleen whale consumes a huge mouthful of krill, small fish, and water, it partially shuts its jaws and then presses its tongue against its upper jaw to force the water through the baleen, leaving the krill and fish on the inside of the filter for the whale to swallow.

This strategy was co-contributed by EcoRise Youth Innovations.

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“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 HistoryJanuary 3, 1970
David Attenborough

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