Measure of a shark’s ‘chomp’

 
The jaws of a great white shark can inflict a bone-crunching bite of up to 1.8 tonnes, according to Australian researchers. The predator's chomp is around three times more powerful than a lion's, at least 20 times stronger than a human's and just over half as strong as Tyrannosaurus rex. But today's largest predatory fish would have come off much worse against a now extinct leviathan of the deep called Carcharodon megalodon, or "big tooth," which died out 1.5 million years ago. At 16 metres long and 100 tonnes, it would have put Jaws to shame, and the new analysis suggests that its colossal mouth could have produced a bite force of 10.8 to 18.2 tonnes."Nature has endowed [the great white shark] with more than enough bite force to kill and eat large and potentially dangerous prey," said Stephen Wroe at the University of New South Wales in Sydney. "Pound for pound, the great white's bite is not particularly impressive, but the sheer size of the animal means that in absolute terms it tops the scales. It must also be remembered that its extremely sharp serrated teeth require relatively little force to drive them through thick skin, fat and muscle," he said.Trying to measure the bite of a live shark might sound like suicidal devotion to your field of science. The researchers got around the danger by using an engineering technique called finite element analysis. The method, which is used widely in building and car design, involves creating a computer model of the passage of stresses and strains through a material. The first step is to create an accurate 3D digital representation of the skull or fossil — in this case the skull of a 2.4 metre long male shark — using an X-ray scanning technique called computer tomography. This 3D shape is then broken up into tetrahedral blocks or "elements," which are linked together and react realistically to stresses and the movements of nearby elements. In this way, scientists can apply imaginary forces to the structure and work out what stresses the shape can withstand. The results are reported in the Journal of Zoology. The technique was first applied to biological structures by Emily Rayfield at the University of Bristol in 2001. She first analysed the skull of Allosaurus, a carnivorous dinosaur, but later applied the technique to T rex.

The Hindu, 5th August 2008