The marine biologist picks his way down a mud ravine into the belching, bellowing madness of Cardwell Point.

All eyes are upon him, this short ruddy creature with an orange jacket, red beard and sturdy legs that seem to glide effortlessly across the sand.

Brent Stewart has studied elephant seals for 31 years and knows they are watching him. He scans the wind-scoured sand spit for rogue bulls -- bilious giants of blubber, muscle, whisker and teeth. They come here from the deepest, coldest reaches of the North Pacific to mate, and they don't like interlopers.

Stewart has witnessed epic battles among them, pendulous snouts flailing like medieval maces, chunks of bloody flesh flung into the air, deep thwacks piercing the endless din of the wind. There is no way not to ponder the fragility of the human spine in such moments.

He walks warily into the fray this February afternoon, hundreds deep, keeping an eye open for escape routes.

"They're quiet and sneaky," he says. "When their eyes get all scrunched up, that's when you want to run."

As a senior scientist for Hubbs-Sea World Research Institute, Stewart has studied all types of sea life, in the waters off Antarctica, Greenland, Russia, the uninhabited outer Hawaiian Islands, the Maldive Islands in the Indian Ocean, Alaska, Iceland, Mexico.

After all that, he still marvels at what he sees every winter so close to home.

"How many people do we have now?" in Southern California, he says. "Twenty million. Just offshore, we have the most diverse area of seabirds and sea mammals anywhere in the world."

Late January and February is the time to behold it, when the elephant seals haul up and fill the beaches, after the longest migration of any mammal on Earth.

Year after year, Stewart takes in the spectacle mostly alone.

San Miguel Island, the westernmost of the Channel Islands, 25 miles off the Santa Barbara coast, is raw. No one lives here permanently and few people visit. Ocean swells blast the jagged shoreline, making it impossible to land a boat most of the year. The relentless wind drives sand and grit over the 15-square-mile hump of land, raking scars through the scrub and stunting the indigenous shrubs.

Stewart, 55, figures he has spent eight or nine years of his life out here.

When he started in 1979, northern elephant seals were a mystery -- otherworldly pinnipeds larger than walruses. In the early 20th century, scientists had thought they were gone, hunted out of existence for their blubber. By the time Stewart came on the scene, they were rebounding, colonizing beaches for several months a year on San Miguel, San Nicholas Island 70 miles south and remote stretches of the Central Coast.

No one knew where they went for the other nine or so months. The assumption was that they were feeding just off the coast.

Stewart and Robert De Long, a marine biologist with the National Oceanic and Atmospheric Administration, began to attach depth and light sensors to the animals in the late 1980s to see what they were up to.

Of the first eight depth sensors they recovered, four had been flooded out. The underwater pressure had blown out the rubber gaskets.

What they learned over the ensuing years was astonishing: When the seals left the Channel Islands, they headed far into the northern Pacific, hunting alone. They dived for 20 minutes at a time or more -- sometimes for more than two hours and up to 5,000 feet down. The only other mammals known to reach such depths were beaked whales.

The seals would surface for about three minutes to breathe and then go back down, repeating the cycle for months on end before returning to California in winter to breed and in summer to molt. In one year, they might spend a full nine months at sea, travel 13,000 miles and spend 80% of the time underwater.