Gray Whale , medium-size whale, occurring only in the North Pacific Ocean. Gray whales migrate between their winter calving lagoons off the coast of northern Mexico and their summer feeding areas in the northern Bering Sea-one of the longest migrations of any mammal. The range of gray whales once included the North Atlantic Ocean and the western Pacific Ocean between Japan and the Russian Kamchatka Peninsula (see Kamchatka), but they have since been hunted to extinction in the North Atlantic, and to near extinction in the western Pacific. Gray whales may attain lengths of up to 15 m (up to 49 ft). They have a fleshy dorsal hump two-thirds of the way from the front of the body, but no true dorsal fin. The skin is mottled black, gray, and white, and this distinctive color pattern can be used to identify individuals. The whales are usually covered with barnacles and whale lice. The diet of gray whales consists mainly of invertebrates that live in the muddy bottom of the Bering Sea. The whale s in mud along with the prey, then expels the muddy water by pushing its powerful tongue against short, bristly, yellow baleen plates that hang from the edges of the upper jaw and act as a sieve. Huge quantities of mud and food particles are expelled after a feeding dive, and seabirds often feed on these expelled food particles. Gray whales also in clouds of invertebrate prey from the water column, but they more commonly feed on the bottom. Mature females may give birth once every two years. The mating season usually occurs during November or December. Gray whales appear to have a polygamous mating system. A single calf is born after a gestation period of 12 or 13 months and is nursed for seven or eight months. Males do not appear to play a role in caring for their young. Gray whales are slower swimmers than other whales and stay near shore in almost all parts of their range. They have therefore been subject to relentless whaling and were hunted nearly to extinction in the 1800s and again in the early 1900s. Except for an annual Siberian Inuit harvest of about 170 to 200 whales, the hunting of gray whales has been forbidden by the International Whaling Commission since 1947. As a result, gray whales, alone among the baleen whales, have made a remarkable recovery to a total population of more than 20,000 animals in the 1990s. They are a favorite tourist sight off the coasts of California, Oregon, and Washington states from November through April or May, when mothers and newly born calves migrate northward. The gray whale is classified as an endangered species .