Polar bears under threat: Now sharks are after them too

Already threatened by a thaw of ice around the North Pole, the polar bear's title as the top Arctic predator may under challenge from a shark.

Scientists researching how far sharks hunt seals in the Arctic were stunned in June to find part of the jaw of a young polar bear in the stomach of a Greenland shark, a species that favours polar waters.

"We've never heard of this before. We don't know how it got there," Kit Kovacs, of the Norwegian Polar Institute, said of the 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."