Gray Whale

Eschrichtius robustus

Description

The gray whale, Eschrichtius robustus, is a moderate-sized baleen whale, 36-46 ft (10.8-13.8 m) in length. A slow swimmer, the animal is typically covered with many encrustations on its back. The body is blotched grayish black and slender, with up to five longitudinal throat folds and broad, angular flippers. Where other whales have a dorsal fin, the gray has a series of humps along the tail, called knuckles. Females are somewhat larger than males, weighing in at nearly 7,000 lb (3 metric tons). The California gray whale is another common name for this species.

Behavior

The gray whale migrates farther than any other mammal, traveling as far as 10,000 mi (16,000 km) round-trip from feeding grounds in the Bering and Chukchi seas to breeding grounds off the coast of Baja California and mainland Mexico. Gray whales typically travel in small pods of up to about 15 animals or in cow-calf pairs. The gray whale is a bottom feeder, eating amphipods, isopods, mysids, tube worms, and other bottom-dwellers. While feeding, it scoops up large quantities of sand and rocks, often leaving a muddy trail that is visible from the surface.

The gestation period is 12 months, after which a single calf weighing 1,500 lb (680 kg) is born. Calves are weaned after seven months, and growth is prodigious during the first year. The calf may gain as much as 27 lb (12 kg) per day. Females calve every two or three years.

Emerging from the water, the gray whale spouts from its blow-hole at brief intervals and not more than 10 ft (3 m) high. Its vocalization is in the form of a bubble blast that can be heard 1.5 mi (2.4 km) away.

Habitat

The gray whale is a pelagic mammal that feeds in cool northern waters in summer and breeds in warmer coastal waters in winter.

Distribution

Historically, there were three major breeding populations of the gray whale. A population along the Atlantic coast was exterminated by whalers in the seventeeth century. A small Asian population off the coast of Siberia and Korea has been hunted to the verge of extinction. A third population migrates along the North American Pacific coast and is now protected from whaling.

Gray whales off the Pacific coast of North America have been protected by law since 1946. Nearly extinct at that time, numbers have rebounded steadily to about 16,500, which is close to pre-whaling levels. Until a whaling moratorium went into effect in 1986, about 180 of these North American gray whales were taken every year off the coast of Siberia, primarily by Russian and Japanese vessels. The current status of the Asian population is unknown but probably no more than 200-300 individuals survive.

Threats

One of the easiest whales to hunt because of its slow speed and inshore habits, the gray whale was also one of the first to show the symptoms of species decline. Whalers eliminated the mammals from the Atlantic Ocean within the span of about 50 years. Japanese fishermen in the eighteenth century hunted in small boats, herding the whales toward the beach where they were taken with harpoons and nets. The last gray whale in Japanese waters was taken in 1933.

Conservation and Recovery

The gray whale was first protected in 1937 by an international agreement and again in 1946 by an international treaty, although there were many violations of these agreements. The International Whaling Commission (IWC), which has regulated the whaling practices of 38 member countries since 1946, called for a total moratorium on whaling in 1986, which has been mostly successful. Soviets whalers, reacting to international criticism of their whaling practices, sought to repair their image in the fall of 1988, when their icebreakers made a heroic effort to free three gray whales trapped in Arctic ice. The U.S. Coast Guard had failed in an earlier attempt to free the whales.

Contacts

U.S. Fish and Wildlife Service
Assistant Director-Fisheries
Main Interior
1849 C Street N.W., Room 3245
Washington, District of Columbia 20240-0002
Telephone: (202) 208-6394
Fax: (202) 208-4674

National Marine Fisheries Service
Department of Commerce
Washington, D.C. 20235

References

Baker, M. L. 1987. Whales, Dolphins, and Porpoises of the World. Doubleday, Garden City.

Evans, G. H. 1987. The Natural History of Whales and Dolphins. Facts on File, New York.

Hoyt, E. 1984. The Whale Watcher's Handbook. Doubleday, Garden City.

Mead, J. G., and E. D. Mitchell. "Atlantic Gray Whales." In M. L. Jones et al., eds., The Gray Whale. Academic Press, New York.

Oliver, J. S., et al. 1984. "Gray Whale Feeding on Dense Ampeliscid Amphipod Communities near Bamfield, British Columbia." Canadian Journal of Zoology 62:431-49.