Giant Sea Lion Called a Natural-Born Killer

This sea lion’s behavior has been anything but gentlemanly.

An unusual hybrid, the “Marauder of San Miguel Island” is believed to have killed up to 50 female sea lions annually over the last five years by suffocating his partners with an overzealous mating technique.

For years on this most remote of the Channel Islands, 55 miles off the Ventura County coastline, marine biologists were baffled by the mysterious springtime deaths of adult female sea lions, all found clumped in one cove off the northwest shore of the island.

Enlisting the help of the Coast Guard and Channel Islands National Park rangers, biologist Robert DeLong set up a surveillance system.

They watched fishing boats from the ocean and the air, suspecting that fishermen might be shooting or clubbing the sea lions.

They also considered the possibility of an underground explosion or pollution as the cause of death, but the concentration of the bodies in such a small area seemed to rule that out.

“Nothing seemed to fit,” said Chief Ranger Jack Fitzgerald.

Biologists did necropsies--the animal equivalent of an autopsy--on the bodies of about 30 female sea lions in the spring of 1994.

But the tests yielded no answers and the puzzle went unsolved until last spring, when the hybrid was caught in the act by DeLong, offshore in a patrol boat.

“I saw him in the middle of a copulation with an adult female,” DeLong said. “He suffocated her. She was still alive when he dismounted, but died later.”

Last season’s damage was already done by the time the creature was identified as the culprit.

But with mating season just now beginning, rangers and biologists will be keeping an eye out for the return of the sea lion. They are half-hoping he met his end while wintering in the cool waters of the Northwest so they don’t have to decide whether to shoot him.

DeLong said the giant hybrid, a blend of a smaller California sea lion and a Steller sea lion, could weigh up to 1,800 pounds. The average weight for the female California sea lion is about 220 pounds. While the female is used to mating with male California sea lions ranging from 700 to 1,000 pounds, the giant hybrid is too large for her.

But the sheer size of the “fluke of nature,” as DeLong calls him, is not the only factor involved. Mixed signals and bad timing are also to blame.

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He said his best theory is that the hybrid was born of a Steller sea lion father and a California sea lion mother who somehow survived the experience. San Miguel Island was traditionally the southernmost range for the Steller sea lions, but a radical drop in the numbers of the breed in the last two decades has left the Channel Islands virtually devoid of appropriate mates for the hybrid.

So he turns instead to the smaller Californias. And not only is he oafish about it, his timing is off. Stellers start to breed in late May and June, whereas California sea lions mate in July.

“His timing is more Steller than Californian,” DeLong said.

Because the females aren’t ready, they don’t respond properly when approached by the hybrid. Typically, the male mounts the female and restrains her down with his weight until she sends a signal that she is ready. Then he lifts himself up on his foreflippers, easing the load on her.

“If that male were to support his weight on his foreflippers rather than lying prone, the females could survive,” DeLong said.

But the hybrid giant never gets the signal, so his poor mates end up squashed.

DeLong said there is no way of knowing if the hybrid has mated successfully in the past. It is quite possible that he is sterile, he said.

“The important thing that needs to be said is that he is a mistake of nature,” DeLong said. “This is not the way evolution occurs. If there are any progeny, those progeny are going to make those same mistakes he is making.”

One way to save further females from death is to kill the hybrid. But DeLong has not applied for a permit to shoot the creature.

“I do see a point in doing so,” he said. “But internally there are still some discussions about the merits of doing so or letting it go as a natural phenomenon.”

Officials at the Humane Society of America said they hope it is not necessary to kill the giant sea lion.

“Clearly there is a problem and clearly he should be stopped,” said Naomi Rose, a marine mammal expert with the Humane Society of America. “But I would really challenge those wildlife managers to try and come up with a more creative solution than shooting him. Grabbing first for the rifle always bothers me.”

Rose said the 60% drop in Steller populations in recent years has been linked to overfishing. Therefore, she said, humans are directly responsible for the creation of the hybrid and for the scarcity of proper mates for him on San Miguel Island.

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“This animal is a freak of nature,” Rose said. “He is really our fault. We caused the fishery to crash.”

For human beings to respond by shooting the animal “sits poorly with me,” she said.

But all these fears may be moot. DeLong said the hybrid is certainly getting old. Adult Steller males usually reach full sexual maturity at about age 10. Since the hybrid has been killing females on San Miguel for about five years, he is probably about 15.

Officials have their fingers crossed that the hybrid has met his end naturally over the course of the winter.

“He could have been eaten by a whale or a shark or hit by a power boat,” ranger Fitzgerald said.