Why do sharks attack humans

The killer from the deep �

A.� Simple. They're killing machines. They hunt for food. It's the same reason that your domestic moggy catches sparrows. That's what they were made to do. The most ferocious is the great white shark.< xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

�

Q.� Is that what attacked the boy in Florida recently

A.� No. That was a bull shark. It's unlikely he would have survived a great white. But more of that remarkable attack later. Back to the great white. In fact, it's grey - only the underbelly is white. This frightening predator has 3,000 teeth that are serrated and up to 3in long. The average great white is between 12ft and 16ft long, although the largest recorded was 23ft.

�

Q.� What does it eat

A.� Young great whites eat fish, rays, and other sharks. Adults eat larger prey, including sea lions, seals, small-toothed whales, otters, and sea turtles. They do not chew their food. Their teeth rip prey into pieces that are swallowed whole. The teeth are in rows that rotate into use as needed. As teeth are lost, broken, or worn down, they are replaced. And then there are the shark's senses...

�

Q.� Efficient, are they

A.� Superlative.�Sharks primarily use their sense of smell; then they sense electric charges. The shark can also sense changes in water pressure. The great white's nostrils can smell one drop of blood in 25 gallons of water.

�

Q.� But how do they sense electrical discharges

A.� By a series of jelly-filled canals in the head called the ampullae of Lorenzini. These allow the shark to sense the tiny electrical fields generated by all animals, from muscle contractions

�

Q.� And most attacks are fatal

A.� No. Great white attacks account for about up to a half of 100 annual shark attacks. Of these 30 to 50 attacks, between 10 and 15 people die.

�

Q.� What about the attack on the child in Florida

A.� That was incredible. The attacker was a 7ft bull shark. The eight-year-old boy was attacked in the surf at Fort Pickens. The shark ripped his arm off and swallowed it. The lad's uncle wrestled the shark to shore with the help of another beach bather.

�

Q.� What

A.� Yes, real heroism here. A ranger then shot the shark and prised its jaws open with a police baton while a volunteer fireman pulled the arm out of the shark's gullet. The boy was kept alive by his uncle and aunt, who staunched the bleeding, and he was flown to hospital where surgeons re-attached the arm.

�

Q.� Incredible. What about series of attacks like in the Jaws film Do they really happen or are they one-offs

A.� The most famous shark hunt was in New Jersey in the summer of 1916. First victim was young stockbroker Charles Vansant, on holiday in Beach Haven with his family. He was attacked as he played in the sea with his dog. Despite the best efforts of his father, a Philadelphia doctor, he died. Ten days later, along the coast at Spring Lake, a bather lost both his legs and died before he could be brought ashore. Then two boys were killed up Matawan Creek, off Raritan Bay, when one of the lads tried to rescue the other.

�

Q.� Was the killer shark ever found

A. Two days after the double-death at Matawan Creek, an 8ft great white shark was hooked and dragged on the boat. The killing ended ... but half a century later, a man called Peter Benchley read the New Jersey reports and had a great idea for a novel. He called it Jaws.

�

To ask a question about Animals & Nature, click here

By Steve Cunningham