Scientists Find Whales "Eating Themselves Stupid" On Krill - But Ice Decline May Cut Future Feasts

[hatrack]

In the last two years, researchers at first hoping only to tag a few whales have happened onto hundreds of humpbacks eating themselves stupid in the bays of West Antarctica.

In the Southern Hemisphere fall of 2009, Wilhelmina Bay on the Antarctic Peninsula held at least 306 humpbacks, the densest crowd of the whales scientifically documented in one place, says biological oceanographer Douglas Nowacek of the Duke University Marine Lab in Beaufort, N.C. Another bay on the peninsula also hosted a big crowd, and a research visit to Wilhelmina Bay in 2010 found abundant humpbacks too.

These whales spent their nights feasting on the dominant Antarctic species of shrimplike krill, Euphausia superba, Nowacek and his colleagues report online April 27 in PLoS ONE. The researchers ranked the 2009 krill gathering in Wilhelmina Bay as the largest aggregation of E. superba documented in the Antarctic in 20 years. An estimated 2 million tons of the petite krill, in some places bunching 2,000 individuals into one cubic meter, were having their own feast on even tinier planktonic life concentrated in the bay by wind and water currents.

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Climate change may be giving those whales an extra, but temporary, bonus. Krill are thought to take cover under seasonal ice. Yet the region’s ice cover now takes around 54 days longer to form than it did in 1979, says a 2008 study. That delay allowed the humpback crowd an extra 3,225 to 7,224 tons of krill in 2009, the researchers calculate. As big as such a feast sounds, they say it’s barely over a third of one percent of the total krill that surrounded them in Wilhelmina Bay that year. The bad news, though, is that the feasting may dwindle. Researchers have reported that low ice cover one season typically foretells a krill dip the next.

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http://www.sciencenews.org/view/generic/id/73676/title/Antarctic_humpbacks_make_a_krill_killing_

[Mnemosyne]

1. I wonder if there is an instinct telling them to "eat themselves stupid" in light of

low ice cover foretelling krill 'dip' next year. Don't mean to be ignorant in this, but really wonder if there are indicators which drive this kind of feeding by the whales.