Why Can't We Be Friends?

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But these are terrestrial and mundane risks. Sharks lurk in the vast, mysterious ocean, an element that still stirs mythic fear. Science is shedding light on why sharks behave the way they do. Researchers are tracking sharks via satellites and coming closer to understanding why they attack humans. The three large sharks that account for most attacks on people--the great whites, the tigers and the bull sharks--have been studied extensively. We now know that great white sharks keep their blood warmer than the surrounding water, that tiger sharks do not return to the site of an attack to prey again, and that bull sharks have the highest levels of testosterone measured in any creature, land or sea. Each has a different diet, a different behavior pattern and a different mode of attack.

Scientists ultimately hope to de-mythologize sharks, to erase their images as rogue man-eaters like the great white shark that figures in Jaws, the Peter Benchley novel turned Steven Spielberg movie classic. Benchley, who says he is now "a full-time ocean conservationist," told TIME last week, "I couldn't write Jaws today." After 25 years of research, the demonization of sharks doesn't hold, he says. "It used to be believed that great white sharks did target humans; now we know that except in the rarest of instances, great white shark attacks are mistakes." Dr. Robert Lea, a marine biologist working for the state of California, goes further: "I used to call them shark attacks--now I call them incidents. It is not a case of sharks preying on humans. It is just humans sharing a spot in the ocean with sharks--at the wrong time."

Sharks are one of nature's ultimate designs, tested over 400 million years--confident, sleek and lethal (see graphic). Studies show some sharks can measure changes in electric currents as tiny as five-billionths of a volt. They use this ability to hunt for prey hidden under the sand and to navigate according to the earth's magnetic field. "They are like some high-tech AWACS thing, with all their sensors," says Sean Van Sommeran, executive director of the Pelagic Shark Research Foundation in Santa Cruz, Calif. When they do attack a human, the weight of evidence now suggests, they have mistaken a person for a seal or some other prey, and most often will spit out human flesh after the first bite. The problem is, of course, that the one bite comes from jaws that are up to 3 ft. across and lined with hundreds of knives.

--THE GREAT WHITE Scott Yerby never saw the great white shark before it attacked him as he surfed off Clam Beach near Eureka, Calif. "This thing jumped me--it had enough force to lift me right out of the water. It was on my leg, I could see my femur, there was blood in the water--I knew then it was pretty serious," says Yerby, who was 29 at the time of the August 1997 attack. He hit the shark on the nose (the prescribed last-ditch defense, along with ripping at its gills), managed to get back on his board, and with his surfing buddy, paddled back to shore. By the time an ambulance got him to the hospital, doctors said, he had lost almost half the blood in his body and was close to death. As he recovered from his wounds in the hospital, many of Yerby's visitors asked him if he intended to go out and hunt down the shark that attacked him. "I said I had no reason to--he was in his element," says Yerby.