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Scientists can't figure out how whales catch squid
www.chinaview.cn 2007-06-29 14:41:39
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    BEIJING, June 29 (Xinhuanet) -- When it comes to catching squid, which have a keen sense of smell, very good eyesight, and can squirt dark ink to hide their escape, humans could learn a lot from whales -- but whales aren't talking.

    "The numbers of squid that are eaten by sperm whales far exceed those harvested by men for food on a worldwide basis," said squid-expert Roger Hanlon of the Marine Biological Laboratory in Woods Hole, Massachusetts.

    But how whales manage to find and devour skiddish squid remains a mystery. One hypothesis, proposed more than 20 years ago, speculated the whales used powerful ultrasound shrieks to knock their squid prey senseless before gulping them down. Like bats and dolphins, some whales use ultrasonic clicks to find prey and navigate.

    A new study by Hanlon and his colleagues reveals squid cannot be paralyzed by whale ultrasound. In fact, they are not even aware they are being targeted. The team's findings are detailed in the July 7 issue of the journal Biology Letters.

    The researchers played recorded ultrasound whale clicks to several long-finned squid (Loligo pealeii) swimming in a water tank. This species of squid grows to about a foot long and is commonly found off the coast of the northeastern United States.

กก  The ultrasound clicks were broadcast at up to 226 decibels, which is about the most intense whale echolocation click a squid would be exposed to in the wild. Not only were the squid not knocked senseless, they did not react at all to the ultrasound bursts, and actually swam in front of the speaker as if nothing were happening.

    "That's like a Bose commercial where you're sitting there and your hair is straight back because the sound is blasting out," Hanlon said. "That to us was a stunning result. We did the experiment several times over because we could hardly believe it ourselves."

    So if whales don't use sound waves to knock out squid, how do they catch them?

    "Why can't [squids] see some aspects of this big whale heading down on them at a zillion miles an hour? That's a big mystery," Hanlon said.

    (Agencies)

Editor: Gareth Dodd
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