Baleen whales use baleen plates to strain food from seawater.
Baleen is made of keratin, the same structural protein found in human hair and fingernails. Plates grow in rows from the upper jaw, with frayed inner edges that form a filtering fringe. Whales take in large volumes of water, then push the water out through the baleen while retaining krill, small fish, or other prey.
This feeding system distinguishes mysticetes, or baleen whales, from odontocetes, the toothed whales. Humpback whales, blue whales, fin whales, bowhead whales, and right whales all use baleen, but their plate arrangement and feeding methods differ.
Baleen is not bone, despite its rigid appearance. Nor is it the same as the gill rakers found in some fish. Baleen whales do not chew their prey; they swallow the concentrated food after filtering the water.