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article imageGray whales survived global warming, cooling by changing diets

By Elizabeth Cunningham Perkins     Jul 8, 2011 in Science
Scientists now believe California gray whales survived global warming and cooling cycles over millions of years, because they are not picky eaters, or stubborn migrators. Flexibility may allow the species to win a new round of climate changes, they say.
After analyzing how the California gray whale responded to 120,000 years of cycling colder and warmer climate changes, compared to how they are behaving now, researchers from the University of California, Berkeley, and the Smithsonian Institution concluded the species adopted generalist filter-feeding modes and shifted migratory behavior to weather the disappearance of their normal feeding grounds, the UC Berkeley News Center reported.
According to additional information published on the UC Berkeley website, and a paper, co-authored by UC Berkeley biologist David Lindberg and Smithsonian paleontologist Nicholas D. Pyenson, published July 6 in PLoS ONE:
Two to four times more gray whales than today's population of about 22,000 swam the Pacific coastal waters before humans arrived. After 75 years of whaling, they numbered fewer than 1000, but protective measures that began in the 1930s allowed the population to rebound, a true conservation success story.
The gray whales of earlier geological ages consumed a wider variety of foods, allowing their numbers to remain high, despite periodic global warming and icing, so the species' avoided "population bottlenecking" (interbreeding within severely reduced populations), and retained sufficient genetic diversity to ensure survival.
Today's gray whales are beginning to utilize more food resources, such as krill and herring, and some are shifting migratory patterns, or dropping out altogether. The researchers noted that one group has begun living year-round off Canada's Vancouver Island.
Before this research, most scientists thought gray whales fed only by suctioning and filtering benthic organisms, such as amphipods and worms, out of ocean floor sediment.
According to Animal Diversity Web:
Gray whales inhabit the western and eastern north Pacific Ocean.
The eastern north Pacific gray whales feed in shallow arctic waters during the summer, and migrate southward along the North American west coast to winter calving grounds off Baja California.
People living on the western shores of British Columbia and the United States often spot migrating eastern gray whales.
Western Pacific gray whales inhabit the waters of the Okhotsk Sea, and the coastal waters of Russia, North Korea, and South Korea. The western gray whale populations have not been studied as much, and are relatively poorly understood.
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