August 11, 2008

Top Predator: Polar Bear Or Shark

Known as top predator in its icy terrain around the North Pole, the polar bear could be at risk of becoming prey to another predator: the shark.

Scientists at the Norwegian Polar Institute were trying to gauge the effect of massive thawing at the North Pole on how far sharks hunt seals in the Arctic. In June they made an unexpected discovery when they found part of the jaw of a young polar bear in the stomach of a Greenland shark.

"We've never heard of this before. We don't know how it got there," Kit Kovacs, of the institute, said of the 10 cm (4 inch) bone found in a shark off the Norwegian Arctic archipelago of Svalbard.

"We can't say whether or not the shark took a swimming young bear" or ate a carcass, she said. "We don't know how active these sharks are as predators."

However, most scientists hold to the assumption that the young bear was dead before the shark found it.

"It sounds like a scavenge," said Steve Campana, head of the Canadian shark research laboratory at the Department of Fisheries and Oceans.

He said he had not heard of a shark eating a bear before and it was a "million dollar question" for researchers as to whether Greenland sharks attack live bears.

This is not the first time scientists have discovered unexpected animal bits in the stomachs of Greenland sharks. Parts of caribou have been found in the past.

Campana said there was even a myth that the sharks could leap out of the water and seize caribou standing on ice.

"There's no possibility a Greenland shark could predate a live adult white bear unless it was injured or seriously ill," said Jeffrey Gallant, co-director of a Canadian-based Greenland shark education and research group.

Sonja Fordham, deputy chair of the shark specialist group of the International Union for Conservation of Nature, said more research was needed into the Greenland shark's habits.

"Greenland sharks do seem quite sluggish ... but they have been known to move very quickly when they are eating," she said.


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