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GRAY WHALE (Eschrichtius robustus)

RANGE. Shallow coastal waters of eastern North Pacific, Bering and Chukchi Seas.

Each year, gray whales of the eastern North Pacific Ocean make an epic 16,000- to 23,000- kilometer (10,000- to 14,000-mile) migration between their Arctic summer feeding grounds in the Bering and Chukchi Seas and their winter calving grounds in the warm lagoons of Baja California, Mexico. In summer, gray whales bulk up in the Arctic waters between Alaska and Siberia, scooping up gigantic mouthfuls of mud from the ocean bottom and filtering out crustaceans and tubeworms with their baleen. Gray whales play an important role in the Arctic ecosystem due to their unique style of bottom-feeding. They create gigantic mud plumes that re-suspend large volumes of nutrients, which in turn enrich life on the seafloor and bring a bounty of bottom-dwelling crustaceans to the surface for seabirds to feast on.

The eastern North Pacific gray whale was removed from the U.S. endangered species list in 1994 when the population reached 23,000 individuals and was thought to have recovered from decimation by commercial whaling. Subsequent genetic research concluded that the pre-whaling abundance likely ranged from 76,000 to 118,000 individuals, indicating that the current population is still far from full recovery. [1] In addition, since 1998 when gray whales reached a peak of 29,758 animals, the population has undergone a severe 40-percent reduction, a mass starvation event, and ongoing changes in migration patterns, calving locations and feeding behaviors. [2] Many of these changes have been linked to shifting ocean conditions, making ocean climate change a new challenge to the gray whale’s recovery.

The rapid loss of sea ice appears to be lowering the abundance of gray whales’ bottom-dwelling prey on its traditional Arctic feeding grounds in the northern Bering Sea. [3] Some researchers have warned that this region will be able to support fewer whales as the food supply declines. [4] Gray whales are also beginning the southbound journey to their calving lagoons later, perhaps because they need to travel farther and feed longer in the Arctic before embarking on their energy-intensive migration. [5] As a result, more whales are giving birth while in route to the calving lagoons, and are spending less time in the protected lagoons nursing their young. [6] More whales are also cutting their northbound route short and spending more time in heavily trafficked and polluted waters off the U.S. coast where food supplies may not be sufficient.


1. Alter, S. E., E. Rynes, and S. R. Palumbi. 2007. DNA evidence for historic population size and past ecosystem impacts of gray whales. Proceedings of the National Academy of Sciences of the United States of America 104:15162-15167.
2. Moore, S. E. 2008. Marine mammals as ecosystem sentinels. Journal of Mammalogy 89:534-540.
3. Grebmeier, J. M., J. E. Overland, S. E. Moore, E. V. Farley, E. C. Carmack, L. W. Cooper, K. E. Frey, J. H. Helle, F. McLaughlin, and S. L. McNutt. 2006. A major ecosystem shift in the Northern Bering Sea. Science 311:1461-1464.
4. See 1.
5. Stafford, K. M., S. E. Moore, M. Spillane, and S. Wiggins. 2007. Gray whale calls recorded near Barrow, Alaska, throughout the winter of 2003-2004. Arctic 60(2): 167-172.
6. Shelden, Kim E. W., David J. Rugh, and Alisa Schulman-Janiger. 2004. Gray whales born north of Mexico:    indicator of recovery or consequence of regime shift? Ecological Applications 14(6): 1789-1805.


Polar bear photo © Jenny E. Ross/ www.jennyross.com