|2010 SUMMER EDITION – NO. 38|
Sea otters were washing up dead in unprecedented numbers on Homer Spit, on Alaska's southern coast, in 2007, and biologists found, at one point, that three-quarters of them had a vegetative lesion on their hearts, an extraordinarily unusual finding for which they had no precedent. The U.S. Fish and Wildlife Service declared an "Unusual Mortality Event" and dispatched a team of biologists and veterinarians to diagnose the animals and the ecosystem.
Veteran researcher Angela Doroff escaped the tourist chaos on the Spit with her team of scientists. Although floating within minutes of the harbor they stayed out for weeks on end to avoid its distractions and entanglements. I boarded the flat steel deck of their chartered vessel from my boat, off Cohen Island, in Kachemak Bay, and looked at the plywood otter surgery built there.
More than half the otters in the Aleutian Islands have disappeared since the mid-'80s — with only ten percent remaining in some former strongholds — so Doroff's project in Kachemak Bay had the urgency of potentially diagnosing the spreading edge of a catastrophe. Otter health also has something important to say about the ecosystem, even for those who hate otters as much as a crab fisherman, who compete with them for their catch.
Otters survive the cold water without an insulating fat layer by the blaze of a prodigious metabolism — my 190-pound body would need 22,000 calories a day to burn fuel at the same rate. Scarce or contaminated food affects otters first. And they are a keystone species, their voracious appetites regulating the near-shore ecosystem in ways that keep it healthy and diverse. "When we lose them in big numbers, either here or in the Aleutians, that should make us think really hard," Angela said.
Diagnosing an ecosystem is absurdly difficult. The strategy was this: catch dozens of otters, perform detailed health exams, tag the animals and install radio tracking equipment in their bodies, then wait for them to die, find the bodies, and do necropsies to find the cause.
We sat together all afternoon waiting for a single otter to allow itself to be caught. They are devilishly intelligent and know well how to size up a net and avoid it. Otters socialize closely, adapt to varying habitat, and use tools to break open shells — they can catch, handle and consume more than 150 different species of invertebrates and fish. A team in a skiff quietly draped a net waiting for an otter to make a mistake, waited for hours, while Angela and I watched from a distance to preserve the quiet, feeling sun pierce through fog that had lingered on the nearby island as if caught in its comb of spruce trees.
Once captured that evening, a female otter — 60 pounds of furious muscle and sharp teeth — would be wrapped up and sedated and given a medical work-up on the ship, including an ultrasound inspection of her heart and surgical insertion of a transmitter in her body cavity. The animal struck me as hauntingly human, as she lay unconscious on the exam table — the absence of fat exposed the shape of her rib cage, and even her organs and muscles seemed familiar under her thin coat, which was softer than any skin and shed tiny hairs to a gentle touch.
Waiting for that otter to be caught, watching the sun and fog pass over the island, Angela told me of growing up in the woods of her father's farm before devoting her life to studying marine animals in Alaska, and the long months of field work that precluded starting her own family. And the job she had of receiving death threats from angry fishermen.
She said Kachemak Bay did seem to be in decline. "We probably are diminishing it. We're changing it. We're changing it every day. We're the biggest keystone species that has come along in a long time. And is it making it better? I think you have to say it is not." But she didn't specifically blame the fishermen. She brought into the issue the lack of scientific knowledge, strawberries in the dead of winter, and the Zip-Loc bag from which I was eating mini pretzels. She said, "We're not very good animals anymore, are we? As an animal in the system? We've done our best not to need nature anymore."
Three years later, just recently, we talked again. The sea otter study was almost done, the last transmitters had just failed, and the results were completely surprising. First, the deaths on the Spit. It turned out Kachemak Bay had far more otters than anyone knew — a new population had migrated in — and so the number being found dead wasn't out of line with what would be expected. Moreover, the health work-ups by Doroff's team showed the otters were getting plenty to eat.
The study didn't really work to figure out the heart lesions. Of 44 tagged otters, only six otters died. Four were killed by humans, either hit by boats or killed (legally) by Alaska Native subsistence hunters. The two that died of natural causes didn't have heart lesions.
But another study made an extraordinary finding that offers the best explanation. A team led by Tracey Goldstein, of the University of California, Davis, found RNA for a phocine distemper virus in otters from the Kodiak Archipelago. The virus wasn't present in Pacific animals in 2000, but had caused epidemics that killed tens of thousands of seals in the Atlantic in 1988 and 2002. Goldstein, Doroff and others believe the virus came with seals through the Arctic from the 2002 epidemic, a journey facilitated by the lack of sea ice due to climate change in the last decade.
Crab fishermen weren't to blame. Everyone who releases carbon dioxide to the atmosphere was — that is, everyone on earth.
Doroff's study is over. Now biologists watch to see if the virus brought over the top of the world will kill thousands of marine mammals here, as it has in the Atlantic.
Photo courtesy Charles Wohlforth.
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