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- SAN FRANCISCO (Reuters) - "Jaws," it turns out,
isn't quite as voracious as we thought.
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- The great white shark, immortalized in
the 1975 movie as one of the natural world's most ruthlessly efficient
predators, actually appears to be a finicky eater with little taste for
humans, new research indicates.
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- "They clearly make a decision on
what they are going to swallow," said Peter Klimley, a marine animal
behaviorist with the University of California-Davis. "Most surfers
they just spit out."
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- Klimley and a group of scientists have
spent the past four years examining the predatory behavior of great white
sharks around rocky outcroppings off the California coast where elephant
seals, their favorite prey, gather.
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- The study, funded in part by the National
Science Foundation and the National Geographic Society, is aimed at getting
a clearer picture of how and why these so-called eating machines attack.
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- Hard-working hunter
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- The results indicate a far more complex
and hard-working hunter than previously thought. "We are getting
insights into the real white shark, which is a bit different from the shark
we were all brought up to be scared of," Klimley said in an interview.
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- "I'm arguing that it's not a feeding
machine. It doesn't just go somewhere and eat automatically because it's
there. It has to work hard to eat, like most animals."
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- The group's research, covered in the
current issue of "Discover" magazine, is among the most detailed
looks at the great white, which can grow up to 20 feet in length and weigh
more than 5,000 pounds.
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- Great white shark attacks are legendary
-- but in fact are rarely fatal. In some 78 attacks recorded along the
California coast since 1926, there have been just eight deaths.
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- Klimley, who had already done extensive
research into the shark's feeding behavior on seals, was intrigued. Great
white sharks feasting on seals hardly pause between bites, engaging in
bloody banquets that turn the seas red and often leave the victim cut clean
through by the shark's rows of teeth.
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- 'Social' sharks?
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- To better understand the shark's eating
habits, Klimley and Burney Le Boeuf, a seal expert at the University of
California-Santa Cruz, went to the islet of Ano Nuevo about 23 miles off
the central California coast, a prime elephant seal rookery and a major
feeding ground for great whites.
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- There, they implemented a system for
getting one of the first sustained looks at great white shark behavior
underwater, "tagging" sharks with ultrasonic transmitters linked
to a sophisticated computer-tracking system.
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- The electronic tags, which were tracked
by a triangle of "sonobuoys" placed 550 yards apart off the western
shore of Ano Nuevo, allowed the researchers to track their subjects day
and night as they hunted in the frigid waters.
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- The initial results have added new details
-- some of them surprising -- to the picture of the shark.
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- First, the commonly held belief that
great whites only hunt during daytime was disproved, with researchers recording
predatory behavior around the clock.
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- Second, the notion that these mammoth
sharks are solitary rogues was also called into question. Scientists observed
an almost "social" connection between shark pairs and discovered
evidence that sharks may try to warn each other off fresh kills by slapping
their tails against the water.
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- "Once they get an item they are
possessive and don't want another shark to get it," Klimley said,
describing the tail slapping communication. "This is certainly adaptive
behavior. If they wanted to defend by biting each other, it would be real
hell with all those teeth."
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- Picky eaters
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- But the researchers said the real surprise
was the great white's picky eating habits. Instead of crunching down with
their jaws, great whites gently "mouth" items that they catch
trying to tell if it might be edible, Klimley said.
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- Animals like elephant seal, which are
covered with soft blubber, are quickly adjudged tasty and consumed. But
other morsels, ranging from buoys and surfboards to sheep carcasses, sea
otters and human surfers, are usually not soft enough to bother with, he
said.
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- "We see attacks where they have
seized people by the leg and carried them through the water before releasing
them," Klimley said. "It has to be carrying the person gingerly
to do that."
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- After testing swimmers with their teeth,
sharks usually release them. "This 'man-eater' usually doesn't eat
man," Klimley said.
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- The next move is to tag more sharks and
begin tracking them over a period of months in hopes of recording swimming
speed, swimming depth and frequency of feeding, Klimley added.
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