The Gray Whale or Grey Whale (Eschrichtius robustus) is a whale that travels between feeing and breeding grounds yearly. It reaches a length of about 16 meters (52 ft), a weight of 36 tons and an age of 50–60 years. Gray Whales were once called Devil Fish because of their fighting behavior when hunted. The Gray Whale is the sole species in the genus Eschrichtius, which in turn is the sole genus in the family Eschrichtiidae. This animal is descended from the filter-feeding whales that developed at the beginning of the Oligocene, over 30 million years before the present.