Gray whales eat a wide variety of crustaceans, such as ghost shrimp and amphipods, along with many other organisms, including polychaete worms, herring eggs and animal larvae. They feed off the ocean bottom, sucking in a large amount of sediment, then forcing it out through their baleen plates. Food items are trapped in baleen filters and are scraped off by the whales' tongues to be digested.
Gray whales are the only known whales to primarily practice bottom feeding, and they generally stay close to shore. They also feed while migrating in open waters. Operating as a group, they herd large schools of small fish into a small area, then take turns moving through the school, ingesting large numbers of them.
Gray whales are able to take in large volumes of water and prey because of their pleated throats, which allow them to expand while feeding. Their upper jaws are longer than their lower jaws, and both jaws bear baleen plates instead of teeth, numbering between 130 and 180 in total. They are a mottled gray in color, and often bear visible infestations of parasites all over their bodies. These parasites include barnacles and whale lice. Adult gray whales range between 36 and 50 feet in length and have a maximum weight of 40 tons.