Elephant Seals Return From Near-Extinction :...

Elephant seals, the mysterious two-ton bellowing giants of the seal family, have rebounded from near extinction and are turning marine biology upside down.

Their rule-breaking physiology could yield clues to everything from sudden infant death syndrome to immune system diseases and even sleep apnea.

A flood of data from sophisticated new instruments has revealed elephant seals can descend a mile below the ocean surface, beating the sperm whale for the sea mammal deep-diving record.

Even more surprising, they spend only two hours out of every 24 on the surface while foraging at sea, violating all known theories about oxygen use, said Burney Le Boeuf, a University of California Santa Cruz scientist and one of the world’s leading experts on the animals.

“There are a lot of paradoxes,” Le Boeuf said. “Elephant seals really threw a monkey wrench into what we understood of diving biology.”

What really confounds marine biologists is that the portly animals almost didn’t survive at all.

The elephant seal, named after the male’s trunk-like proboscis and a ponderous bulk that can reach 5,000 pounds, was pronounced extinct several times at the turn of the century.

In the early 1800s, whalers had reported hundreds of thousands of the animals along the west coast of Mexico and California. But after depleting the whales, the hunters turned on the northern elephant seals.

The seals vanished from all known haunts by the early 1900s. Ironically, each time new herds were found, Smithsonian Museum scientists butchered many of them to ensure samples for posterity.

The population dropped to as low as 20 to 100. Then, in 1922, the Mexican government sent troops to protect the last known herd, discovered on the Isla de Guadalupe off Baja California.

With Mexican and later U.S. protection, the animals spread up the coast. Rookeries now exist on beaches as far north as Oregon, and one elephant seal reached Japan. Le Boeuf says the population, estimated at 120,000, grows by 8% a year.

That makes the elephant seal a success story for conservation.

“Maybe too successful,” said Gary Strachan, supervisor at the Ano Nuevo preserve 50 miles south of San Francisco, one of the largest rookeries.

The animals usually have no fear of man, and unfortunately some humans have no fear of them. Ano Nuevo’s popularity soared after a magazine article about the elephant seals in the mid-’70s, causing a crisis.

“Hordes of people descended on the beach. They were jumping on the elephant seals and riding them,” said Strachan. Ano Nuevo now allows only guided tours, but the elephant seals are spreading to less-prepared beaches.

One tourist was injured by an elephant seal this year on Hearst family-owned property on the Central California coast, and more such encounters are likely as the seals spread, Strachan said.

The allure of elephant seals is understandable. Spectators can watch the awesome spectacle of a two-ton alpha bull slashing the chest of a harem-raiding male rival while emitting guttural roars sounding like a rapid-fire foghorn.

The pups yelp dog-like, the youngest seeking mother’s teat and its 55% fat milk that enables a 75-pound newborn baby to add 200 pounds in a month. The females make almost human cries as they track their young.

“This is the wild--where do you hear the wild anymore?” marveled UCSC graduate student researcher Stacia Fletcher as she stood on the beach at Ano Nuevo with a team weighing pups.

The rookeries fascinate marine biologists. Elephant seal mating is dominated by an alpha male who keeps 24-hour watch over his harem. One season, a study found 5 of the 180 males at Ano Nuevo were responsible for 92% of the inseminations.

The most successful alphas are not always the biggest and boldest. Some smart alphas let other bulls mate with cows at the periphery of the harem--forcing the lower status males to fight off other intruders.

Fletcher said she once saw a wary alpha male escort his females to the sea one by one to ensure they didn’t mate with other suitors along the way.

The biological mysteries begin at the beach.

Baby elephant seals are born into what Fletcher describes as a crowded septic tank of animal waste in the rookeries. And males constantly battle for females, opening large bloody gashes in each other. But neither suffers infections from the dangerous mix of feces, blood and open wounds.

Even when a great white shark tears gaping wounds in elephant seals, the injuries heal quickly and without infection.

“They have a very strong immune system,” said Le Boeuf. If biologists can discover how that immune system works, it might help humans facing immunodeficiency disease such as AIDS.

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Another mystery is the elephant seal’s use of sleep apnea. Apparently to save energy, elephant seals stop breathing for as much as 20 minutes while sleeping. Humans would suffer brain damage from such a long time without oxygen, but the seals inexplicably show no ill effects.

“And if we could identify the signal that tells them to resume breathing, it might shed light on sudden infant death syndrome,” Le Boeuf added.

But the biggest mystery facing researchers is the elephant seals’ unsurpassed diving abilities at sea, where they feed on squid and bottom fish.

Descending below 600 feet will kill any terrestrial animal, but elephant seals plunge a mile and forage under water for as much as two hours. When they surface, they spend only a few minutes before diving again.

“They don’t seem to pay their oxygen debt,” Le Boeuf said.

Scientists theorize that on a deep dive, elephant seals slow down their metabolism and shunt blood only to vital organs such as the heart and brain. They appear to insulate pressure-sensitive brain synapses with nitrogen gas they extract from air and store in their body.

That biology could someday allow surgery without anesthetics, Le Boeuf said.

But it leaves an even more puzzling question.

With metabolism slowed, blood flow restricted and its brain on anesthetic-like nitrogen, how can an elephant seal hunt squid and fish a mile under the sea?

“That’s the big question,” Le Boeuf said.

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Elephant Seal Statistics

* Weight: Elephant seals are the largest of all seals and sea lions, with some males reaching 5,000 pounds. Pups average 75 pounds at birth.

* Population: From a low of 20 to 100 at the turn of the century, numbers are now estimated at 120,000 and growing at 8% a year.

* Range: Rookeries dot the west coast of North America from Mexico to Oregon, and individuals have been spotted as far west as Midway Island and Japan.

* Food: Squid and bottom fish, including skates and small sharks. Seals fast for several months while on land during the breeding season, losing up to 40% of their weight.

* Predators: Great white sharks, killer whales and man, although elephant seals are protected by law.

* Interesting facts: Elephant seals have the deepest confirmed dive of any animal, descending more than a mile below the surface. Their closest diving rivals are sperm whales.

Source: Associated Press