Why Can't We Be Friends?

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The great white is perfectly adapted to its element. Sometimes growing to more than 20 ft. long and up to 4,000 lbs., it keeps its body temperature 5[degrees]F to 10[degrees]F higher than that of the surrounding water by recycling heat from its swimming muscles. This allows great whites to hunt in cooler seas. "It seems to make them more vigorous," says Van Sommeran. The sharks are voracious eaters of seals when they patrol the Red Triangle--a 100-mile strip of California coast from Bodega Bay to Santa Cruz. They have enormous livers to store energy, and can go for months without eating. Nobody has seen great whites mate, but some biologists theorize that after fattening up off the coast, they head into the deep to procreate.

Van Sommeran's team, collaborating with the Point Reyes Bird Observatory and the Hopkins Marine Center at Stanford University, is on the verge of finding where the great whites go after they leave the coast of California in the winter. Since 1999, the biologists have been attaching "pop-up tags" to great whites. These continually measure the shark's position, depth, speed and direction, and store the data in digital archives. After six months, the tiny computer in the tag sends an electric current through a magnesium burn wire, which dissolves in the seawater and allows the tag to pop up to the surface. The tag transmits a GPS locator signal, and when satellites get a fix on it, they upload all the archived data of the shark's movements. The distances are likely to be huge. A shark tagged in Australia in a similar experiment this year traveled more than 1,800 miles along the country's coast in three months.

Great whites are the most lethal to humans. Since 1876 there have been 254 confirmed nonprovoked attacks on humans by great whites, 67 of which were fatal, according to statistics compiled by the International Shark Attack File at the Florida Museum of Natural History. Over the same period, tiger sharks have attacked 83 times with 29 fatalities, and bull sharks have attacked 69 times with 17 fatalities. Great white attacks on humans generally involve just one bite. Researchers are not sure, but most think the shark's sensory organs quickly differentiate between humans and the blubber-rich seals it prefers, so it effectively bites and spits out humans.

Researchers who have been observing great whites off the Farallon Islands west of San Francisco think they know why sharks mistake humans for seals. Peter Pyle, a biologist for the Point Reyes Bird Observatory, notes that the majority of great whites that attack humans are in the 8-to-12-ft. range--inexperienced juveniles making the diet transition from fish to bigger, more nourishing seals. "They are learning a new hunting technique and may mistake surfers for seals," says Pyle. Once the sharks get bigger and more experienced, they appear better able to differentiate between seals and humans.

Unlike tigers and bulls, great whites hunt mostly during the day, and their preferred method of attack is to shoot up vertically from 30 ft. down, knocking their prey right out of the water with the impact. Researchers in South Africa have produced spectacular footage of great whites leaping 15 ft. into the air with a seal in their teeth.