SANTA CRUZ - Great white sharks are not the coastal homebodies scientists thought they were, according to a study from Stanford University and UC Santa Cruz to be published today. During the winter, they travel hundreds, even thousands, of miles across the ocean as far as Hawaii, researchers reported in the journal Nature.

"I was shocked," said UCSC biologist Burney Le Boeuf, one of six marine scientists who spent more than two years on the project. "Going into this, what we expected was that white sharks were just coastal animals that breed in Southern California, then migrate a few hundred miles north to feed on seals," Le Boeuf said. "But it turns out they've got a life at sea, and when they're in the open ocean, they're diving very deep (2,000 feet) at times."

The study was made possible by high-tech developments - electronic tags and computers that can store more information - that enabled scientists to monitor sharks' long-distance migrations.

"Until this study, white sharks had only been tracked for a few days around seal colonies," said Barbara Block, a biology professor at Stanford University's Hopkins Marine Station in Pacific Grove.

The book and movie "Jaws" immortalized the great white shark as a hunter, but scientists wanted to know more about where these predators go, what they do and how to protect them from hunters.

Six great whites - four males and two females - were tagged during the study. They ranged in size from 11 to 15 feet. All six were tagged in the fall, three near the Año Nuevo Island, and three farther north near Southeast Farrallon Island. The sharks prey on the elephant seals that congregate for the mating season.

Peter Pyle and Scot Anderson of the Point Reyes Bird Observatory handled the tagging with the help of Andre Boustany, a Stanford graduate student, and Scott Davis, a graduate student at UCSC. At the Farallons, they launched their boat when they saw a shark feeding on a seal and applied the tag. At Año Nuevo, Davis used a seal decoy made of plywood to lure a shark within tagging distance of the boat.

In the winter, four sharks targeted for long-term tracking headed into the Pacific. One male, nicknamed "Tipfin," traveled more than 2,000 miles from the Farallon Islands off the Golden Gate to the Hawaiian island of Kahoolawe. it stayed in the warmer Hawaiian waters for the entire winter and spring.

Few great white sharks have been seen around Hawaii recently, but ancient cultures had tools made from great white shark teeth, an indication that the islands attracted the predators before.

The others, two females and a male, swam to a subtropical region hundreds of miles west of Baja California, never venturing near the coast. Le Boeuf surmises they too were headed to Hawaii because Tipfin stayed in the same location for 45 days on his way to Kahoolawe, but the tracking devices weren't programmed long enough to find out.

"What they were doing out there is a mystery," said Le Boeuf said. One possibility is a mating rendezvous; another is to seek different prey.

A new shark study is under way by the same team of scientists to answer questions raised by the initial research. "These tags will stay on longer, but we'll have to wait longer to get the information," Le Boeuf said. "We've tagged 11 animals already."

One of them was Tipfin, who was back at the Farallons in November. This time, researchers will monitor his travels for nine months. They also want more information on females. "Males come back yearly, but females return every other year, which means they may be going farther afield than males as part of a two-year breeding cycle," Pyle said.