Published: November 2008
Shore Leave
A rough and randy mating season for the elephant seals of South Georgia Island
By Susan Casey

When it comes to ocean predators, it's easy to underestimate the southern elephant seal. It doesn't have the lordly bearing of the sperm whale or the fighter-jet sleekness of the white shark or the stellar IQ of the orca. Unlike the giant squid or the leopard seal, it lacks an aura of mystery and menace. And who came up with its physique—Dr. Seuss? That would explain the nose, a preposterous trunk that can grow one-and-a-half feet long, earning the elephant seal its name. To judge by appearance, this is one misfit beast. Car-size and blimp-shaped, on land the southern elephant seal (Mirounga Leonine) is usually found lolling around on the beach. But as with other sea creatures, the truth lies below the surface. Sure, it's no supermodel, but underneath the blubbery disguise the elephant seal turns out to be a superhero, its life a series of magnificent feats.

To see where the action takes place, run your finger down a map of South America until you hit Tierra del Fuego and then veer sharply east. Nine hundred miles past the Falklands you'll find South Georgia Island, a hundred-mile-long silhouette of jagged, ice-capped peaks that juts out of what some call the Southern Ocean, the vast belt of water surrounding Antarctica. It's a harsh destination for humans, accessible only by a white-knuckle boat trip that can last five days in South Atlantic gales. But for the seals, which spend 80 percent of their time hunting in these waters, South Georgia is an ideal gathering spot. Come mating season, some 400,000 southern elephant seals will line its shores.

The congregation begins in mid-September, when the first bulls arrive, hauling out on the stony beaches and, almost immediately, starting to fight. These are not minor tussles. They can be bloody battles during which noses are ripped, skin is flayed, and eyeballs end up on the ground. Stakes are high: Only a third of these males will win the chance to breed, a small number considering that they're all loaded with testosterone and equally driven to pass on their genes. Size is definitely a factor here. Bulls can tip the scales at four tons, the weight of a large SUV, and the most colossal males tend to dominate. These turf wars also feature much displaying with that improbable nose, including bellowing with it, puffing it out, and, in general, showing it off.

Scientists refer to the triumphant males as beachmasters—each will control a harem that can range in size from 20 females on the low end to larger conclaves of 300, and in extreme cases, to supersize harems of more than 1,000. When the females arrive in early October and settle down—first to have their pups, then to suckle them, and then, about three weeks after they've given birth, to mate again—part of the beachmaster's job is to protect his females from the unwanted attentions of marauding males. In larger harems a few runners-up find their place around the fringe, but the vast number of vanquished males are left on the sidelines, frustrated and still aggressive. This means more fighting.

"It's definitely not Disneyland out there," says Mike Fedak, a biologist with the U.K.'s National Environment Research Council Sea Mammal Group. "There are significant risks to this whole harem business." This is true not only for seals, but also for humans. As scientists move among the harems, they're careful not to get caught between a beachmaster and his rivals. "You really have to watch yourself," Fedak says. "They can move with amazing agility for animals with no arms or legs."

By late November the party is winding down and the adult seals, which haven't eaten during this time, have lost up to half their body weight. The pups, meanwhile, have gained about ten pounds a day during the three weeks they've fed on their mothers' rich milk. As a female prepares to return to sea, she mates, then weans her pup abruptly, leaving it to its own devices. And then she's gone, pregnant with the pup that she'll deliver next year on these same shores.

Soon the males and the pups will follow her into the water—and this is where the elephant seal reveals itself to be one of the most perfectly adapted predators on Earth. While offshore the seals make journeys of more than 8,000 miles and dive as deep as 5,000 feet, beyond the range of most submarines. For months they hunt for squid and fish, searching for where currents deliver the most nutrients, which in turn attract the rest of the food chain. They can remain submerged for as long as two hours and need only a few minutes of surface time to recover. All this is made possible by some nifty physiological tricks that include shutting off parts of their metabolism to conserve oxygen. Elephant seals are packed with oxygen-rich blood—20 percent of their bodies by volume, almost three times as much as humans.

Given the difficulties of studying a creature that can be found a mile beneath Antarctic sea ice, scientists have recently begun to affix satellite tags to the seals. Along with tracking the animals' movements, the tags deliver an added benefit: They're helping oceanographers figure out the effects of climate change. "There's a real worry right now that ocean-circulation patterns might be changing," Fedak says, describing a scenario that would have massive repercussions for the Earth's weather. "The Southern Ocean plays a critical role in this, and yet it's one of the most data-poor areas. These animals are able to take the devices into places that are unsampled otherwise." Information about water temperature, salinity, and currents in some of the Southern Ocean's least accessible areas is now pouring into the five-year-old Southern Elephant Seals as Oceanographic Samplers program.

So never mind the wacky nose and ungainly body. Gliding beneath a blue icescape, the southern elephant seal is not just going about its business. Like any self-respecting superhero, it's helping save the planet.