Sanctuary Integrated Monitoring Network
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Species Database

Eschrichtius robustus - Gray Whale

Gray Whale image

Geographic range:

Bering Sea to Baja California, Mexico

Key features:

Gray and mottled skin color.


bay (rocky shore), bay (sandy shore), Continental shelf, continental slope, kelp forest, pelagic zone, submarine canyon

Primary common name:

Gray Whale

General grouping:

Whales, seals and sea lions, otters

ITIS code:


Geographic Range

Range Description:

Eschrichtius robustus occupies water from the Bering, Chukchi and western Beaufort Seas to Baja California, Mexico.

Maximum depth:

150 meters OR 499.5 feet

Subtidal depth notes:

Eschrichtius robustus occurs most frequently in shallow coastal waters.


bay (rocky shore), bay (sandy shore), Continental shelf, continental slope, kelp forest, pelagic zone, submarine canyon

Habitat notes:

Eschrichtius robustus generally inhabits coastal waters, migrating close to shore, and calving in shallow southern lagoons. Some move further offshore in summer.


Relative abundance:

Eschrichtius robustus was once found throughout the Northern Hemisphere, but became extinct in the Atlantic a few hundred years ago and now occurs only in the North Pacific. Today the North Pacific has two populations, one in the east and one in the west. The eastern population is referred to as the California stock and is abundant with 26,000 animals, which is believed to be their carrying capacity. The western population is known as the Korean stock. This stock is considered rare with only 400 animals remaining and is one of the most critically endangered whale stocks in the world.

Species Description

General description:

Eschrichtius robustus is known for making one of the longest annual migrations of any mammal, traveling about 8,000 km from its northern summer feeding grounds to winter calving areas in relatively warm water. Eschrichtius robustus is the only species in the family Eschrichtiidae. Eschrichtius robustus was once called devil fish because of their fighting behavior when hunted and the ferocity in which females will defend their calves against predators.

Distinctive features:

Eschrichtius robustus has a large body with a mottled gray coloration, with calves being darker in color than adults. The head of Eschrichtius robustus is narrow and triangular when seen from above. The mouth appears slightly arched and contains 130 to 180 yellowish baleen plates per side. The baleen is relatively short, to about 25 cm long, and has coarse bristles on the inner fringe. Instead of a dorsal fin, Eschrichtius robustus has a hump followed by 6 to 12 bumps along the top of the caudal peduncle. Barnacles and lice grow in various places on the body, but are usually most obvious on the head. Eschrichtius robustus frequently raises its broad mottled flukes during a deep dive. The blow of this species can be either columnar or bushy in shape.


At birth Eschrichtius robustus is 4.9 m in length and weigh 680 kg. Adults can grow to be up to 15 m long and weigh up to 35,000 kg.

Natural History

General natural history:

Eschrichtius robustus can live to be more than 40 years old. Breaching is relatively common behavior in Eschrichtius robustus, although its function is unclear. This species also regularly spyhops (raises its head out of the water) and has been known to exhibit considerable curiosity toward boats.


Juvenile Eschrichtius robustus is sometimes hunted by Orcas. Adult Eschrichtius robustus was heavily exploited beginning in the 19th century. The eastern population has been protected since 1937, but is still hunted by a small aboriginal group in Russia. The western population was hunted commercially by Korea until 1966 and is now only occasionally exploited by Japanese fishermen.


Eschrichtius robustus mostly preys on benthic amphipods, which they filter from bottom sediment in shallow shelf or coastal waters.

Feeding behavior

Filter feeder

Feeding behavior notes:

When Eschrichtius robustus is foraging, it often leaves long trails of mud in their wake on the ocean bottom. They have also been shown to feed on midwater prey, probably more than has usually been assumed.

March - May


The tiny Western North Pacific population migrates north from winter calving grounds off the Korean Peninsula and Japan, to summer feeding grounds in the northern Okhotsk Sea.

October - July


The Eastern North Pacific population of Eschrichtius robustus makes a mammoth migration of 16,000-22,000 km round trip between their southern breeding grounds off Baja California, Mexico and their northern feeding grounds off Alaska and the Beaufort Sea. This is believed to be the longest yearly migration of any mammal.

April - November


Eschrichtius robustus aggregates in Arctic feeding grounds.

October - February


Eschrichtius robustus migrates south, traveling in small groups.

December - April


Eschrichtius robustus aggregates in Mexican breeding grounds.

February - July


Eschrichtius robustus migrates north back to the Arctic feeding grounds.

Monterey Bay National Marine Sanctuary:

Entanglement in fishing gear is considered a threat to Gray Whales and other marine mammals.
Click on an image below to view a larger version in the SIMoN Photo Library. You will also be able to view important information on each photo such as photographer, date, caption and more.
Boschung, H.T., J.D. Williams, D.W. Gotshall, D.K. Caldwell, and M.C. Caldwell. 1998. National Audubon Society Field Guide to North American Fishes, Whales and Dolphins. A.A. Knoph, New York, NY. 848 p.
Reeves, R.R., B.S. Stewart, P.J. Clapham, and J.A. Powell. 2002. National Audubon Society Guide to Marine Mammals of the World. A.A. Knopf, New York, NY. 527 p.