Otters Serve Study in Survival
When Alaskan sea otter No. 600 arrived at Sea World in San Diego nearly one year ago, he was an oily mess. Rescue workers in Alaska had attempted to bathe him, but the otter’s thick fur remained matted with a gooey coating of crude oil--the spilled cargo of the grounded tanker Exxon Valdez.
More life-threatening than No. 600’s soiled pelt, however, were his own efforts to clean it. To maintain buoyancy and warmth, otters continually lick and groom their coats, and No. 600, like many otters caught in the worst spill in history, had ingested potentially fatal amounts of oil.
Luckily for him, the March 24 disaster had prompted Sea World to develop an emergency antidote: powdered charcoal that absorbed the toxins and saved otters’ lives. Today, as No. 600 and five other Valdez survivors tumble and frolic in a Sea World exhibit pool, the charcoal discovery stands out as one of the few positive results of the devastating spill.
“As unpleasant an experience as the Valdez spill was, it proved to be a valuable learning tool,” said Jim Antrim, Sea World’s senior curator of marine mammals. “The treatments we developed in response to this spill could be instrumental, for example, in saving the threatened California sea otter, were a spill to occur in their habitat.”
According to Antrim, only 3,000 California sea otters remain--a fragile population that could be wiped out by a large spill. In contrast, there are about 180,000 Alaskan sea otters, of which at least 1,000 died in the Valdez spill.
Another 300 Alaskan sea otters were rescued from the shores off Bligh Reef in Prince William Sound, rehabilitated and returned to the wild, Antrim said.
But the nine otters at Sea World are unlikely to return to the wild. No. 600 and No. 599, whose names correspond to identification numbers that rescue workers assigned in Alaska, exhibit no obvious lingering symptoms, but are being monitored for long-term effects of oil ingestion. Babe, a 52-pound female, is nearly blind. Katie and three other pups were quite young when captured and have not learned survival skills. Brownie has a bone disease of the rear flippers, and Old Blue has an arthritic spine.
Instead of repopulating Alaska’s waters, then, these otters are helping teach park visitors the importance of protecting habitats. Since Sea World put the Valdez otters on display last summer, the exhibit has developed quite a following--even a group that Antrim calls the “otter spotters,” who visit regularly.
The otters don’t disappoint their fans. Whether chewing on shrimp, crab and clams or doing “whirlies,” rapid underwater somersaults, the otters appear to delight in their 50-foot, 70,000-gallon outdoor pool. Even at rest, floating lazily on their backs as if atop invisible rafts, they are completely at home in the water.
“Talk about the ultimate water bed,” Antrim said, pointing at an otter who seemed to be napping afloat. “They have evolved so they can do literally everything in the water: eat, sleep, mate, give birth, nurse.”
Evolution had not prepared the otters for the 11 million gallons of crude oil that gummed up their home one year ago Saturday.
“It was a like a curtain coming down on them,” said Ron Britton, a biologist with the U.S. Fish and Wildlife Service who worked on the animal rescue effort in Alaska for five months. “Even if they tried swimming under it, they couldn’t swim that far. So they’d surface, draped with this sticky goo, with oil in their eyes, in their mouths. There were probably some that just plain suffocated.”
Others died of exposure when the oil rendered their fur useless. Unlike other marine mammals, sea otters rely on their dense fur--not an insulating layer of blubber--for waterproofing and warmth. Oil-coated otters faced almost certain death from hypothermia or drowning.
In 1985, at the behest of the U.S. Department of the Interior, the Sea World Research Institute had studied techniques for removing oil from otters’ fur. In experiments on 12 otters taken from the wild, scientists applied crude oils to fur and then tried to remove it. Over months, they discovered that repeated applications of dish-washing detergent and water would remove the residue.
So, when five Valdez survivors arrived in San Diego on April 4, 1989, Sea World technicians knew how to clean their coats. They were unsure, however, how to remedy the internal damage suffered by otters that had swallowed oil, and, one by one, four of the five otters died of irreparable liver damage.
Don Kent, executive director of the park’s Research Institute, said that, once ingested, the oil began a vicious cycle in the otters’ bodies. From the stomach, it went to the intestine, where it was absorbed into the blood. Once the blood was contaminated, the liver attempted to cleanse it by secreting bile, which ended up in the intestine and was absorbed into the blood again.
The discovery of the activated charcoal mixture broke that cycle. By binding with the toxic hydrocarbons in the otters’ intestinal tracts, the mixture allowed the animals to expel the poisons from their systems and begin to heal. Nine of the 13 otters that were flown to Sea World have survived.
What long-term effects, if any, the crude oil will have on the otters is the subject of a continuing study, sponsored by Exxon Shipping Co. and conducted by the U.S. Fish and Wildlife service in cooperation with the marine park. Of particular interest is the reproductive ability of the surviving otters.
“A partial success will be if these otters produce young,” Antrim said, as he watched No. 600 and one of the female otters engage in a frantic underwater embrace. “A total success would be if their young could reproduce also. We want to know--were they genetically damaged?”
“It’s a lousy thing to have to learn,” Kent said of the animal rescue techniques his staff helped develop. “We were cleaning up somebody else’s mess instead of doing science. . . . But what it really taught us is there’s no way to totally clean up the mess afterwards. You have to prevent it from happening in the first place.”
