Original URL: http://www.theregister.co.uk/2008/11/25/grays_paradox_undocks/

Boffins crack secret of dolphins' aquatic prowess

Matter of simply being extremely strong, apparently

By Lewis Page

Posted in Science, 25th November 2008 09:49 GMT

American boffins believe they have cracked the scientific riddle known as "Gray's Paradox" - the mystery of how dolphins can manage their amazing physical feats. Famed zoologist Sir James Gray clocked the speedy cetaceans doing better than 20mph in 1936, leading him to theorise that they must have super-slippery hides or some other special seagoing sauce.

“Sir James was certainly on to something, and it took nearly 75 years for technology to bring us to the point where we could get at the heart of his paradox,” said Timothy Wei, a senior prof at Rensselaer Uni’s School of Engineering, who led the paradox-punishing project.

“Now, for the first time, I think we can safely say the puzzle is solved. The short answer is that dolphins are simply much stronger than Gray or many other people ever imagined.”

Marvellous what they can do nowadays, isn't it?

Wei and his boffinry crew are presenting their findings today at a conference in Texas. The allied brainboxes say they have developed a tool that conclusively measures the force a dolphin generates with its tail, showing that Gray's belief that no creature could be that strong was in fact misplaced.

This new state-of-the-art dolphin-clocking technology was made "by modifying and combining force measurement tools developed for aerospace research with a video-based flow measurement technique known as Digital Particle Image Velocimetry, which can capture up to 1,000 video frames per second", it says here.

Wei and his chums used the new kit to videotape a pair of retired US Navy dolphins named Primo and Puka as they swam through a section of water filled with tiny bubbles. They then used specialised software to analyse the movement of the bubbles. The color-coded results show the speed and in what direction the water is flowing around and behind the dolphin, which allowed researchers to calculate precisely how mush force the dolphin was producing.

The same technique was used to film dolphins as they were doing tail-stands, a trick where the dolphins “walk” on water by holding most of their bodies vertical above the water while supporting themselves with short, powerful thrusts of their tails - another physically outrageous thing they shouldn't really be able to do.

The results show that dolphins produce on average about 200 pounds of force when flapping their tail — about 10 times more than Gray originally hypothesized.

“It turns out that the answer to Gray’s Paradox had nothing to do with the dolphins’ skin,” says Wei. “Dolphins can certainly produce enough force to overcome drag. The scientific community has known this for a while, but this is the first time anyone has been able to actually quantitatively measure the force and say, for certain, the paradox is solved.”

It seems that at peak performance, dolphins produce between 300 and 400 pounds of force. This handily trumps human Olympic swimmers, whose best shot is about 60 to 70 pounds, according to Wei. He knows this because he has been working with the US Olympic swim team over the past few years using the same bubble-tracking and force-measuring techniques to coach them.

The prof says his bubble-vid research team hope to go on and analyse other marine animals.

“Maybe sea otters,” he said, quoted in a Rensselaer statement.®