•Genus: Eschrichtius Species: robustus
A young western gray whale off the coast of Sakhalin Island, Russia (Photo: D. Weller)
Gray whales are easy to recognize by their mottled gray and white coloration and dense clusters of a host-specific barnacle that is commonly infested by masses of orange-hued cyamid crustaceans (called “whale lice”) growing on various places on the body, particularly on the head. The unique gray and white coloration pattern, which also extends onto the flippers and flukes, has been extensively used to photo-identify individual animals and to follow them over time, in some cases for decades.
Gray whales are primarily suction-feeders, although not exclusively, consuming a wide range of benthic (sea floor) and epibenthic invertebrates, such as amphipods, that occur in dense colonies in shallow shelf or coastal waters during the summer. When foraging, whales typically roll on their right side with the head slightly above the bottom and swim slowly while suctioning sediment into the side of the mouth and filtering out the prey with their baleen. This feeding behavior creates long trails of water-borne sediment called “mud plumes” which are clearly visible in the water column and on the surface.
Once common throughout the Northern Hemisphere, the gray whale became extinct in the Atlantic by the early 1700s. Gray whales are now only found in the North Pacific where there are two extant populations. Recent genetic studies suggest that these two populations, called the “eastern” and “western” North Pacific populations, are discrete. The eastern North Pacific gray whale population was rapidly depleted by commercial whaling but has successfully recovered from low population numbers and supports a major whale-watching industry along the west coast of North America. The population is presently estimated at about 20,000 animals. In contrast, the western gray whale population, which was also decimated by whaling, remains highly depleted today and its continued ability to survive is of concern. The most recent assessment of this population suggests that about 130 individuals exist. The eastern North Pacific population is listed by the IUCN as “Least Concern”. The western North Pacific population is listed separately as “Critically Endangered”.
The eastern North Pacific gray whale population summers and feeds mainly in the Chukchi, Beaufort and the northwestern Bering Seas. Although most gray whales utilize their Arctic feeding grounds, a small number (100s) of whales summer and feed along the Pacific coast between southeast Alaska and northern California. The population migrates south along the coast in the autumn to wintering grounds on the west coast of Baja California, Mexico, and the southeastern Gulf of California. During winter, large numbers of whales, particularly females with newborn calves, utilize coastal lagoons on the Pacific coast of the Baja peninsula. Gray whales undertake one of the longest annual migrations of any mammal, traveling some 9320 to 12500 miles (15,000-20,000 km) round trip. By late November, most gray whales are moving south from summer feeding areas to winter calving areas.
Both gray whale populations are subject to anthropogenic threats such as entanglements in fishing gear, environmental degradation including exposure to contaminants and disturbance by shipping and noise (e.g. seismic surveys) related to offshore oil and gas development. In addition, the consequences of climate change on gray whales and their habitat, especially the notable reduction of sea ice and increasing water temperatures in the Arctic, are yet to be determined.
Weller, D.W. 2010. Society for Marine Mammalogy - Gray Whale Species Account
IWC 2010. Report of the International Whaling Commission Scientific Committee from its Annual Meeting in 2010, Agadir, Morocco.
Quick Fact Sheet: Gray Whales
Research by Topic:
Eastern North Pacific Gray Whales