High Quality Content by WIKIPEDIA articles! The gray whale, (Eschrichtius robustus), is a baleen whale that migrates between feeding and breeding grounds yearly. It reaches a length of about 15.2 m (50 ft), a weight of 36 tonnes (35 long tons; 40 short tons), and lives 50–70 years. The common name of the whale comes from the gray patches and white mottling on its dark skin. Gray whales were once called devil fish because of their fighting behavior when hunted. The gray whale is the sole living species in the genus Eschrichtius, which in turn is the sole living genus in the family Eschrichtiidae. This mammal descended from filter-feeding whales that developed at the beginning of the Oligocene, over 30 million years ago.