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THE NATION | COLUMN ONE

A Whale of a Food Shortage

The grays, which used to be growing in numbers, have plunged by a third in four years. Now scientists think they know why.

June 24, 2002|USHA LEE McFARLING and KENNETH R. WEISS | TIMES STAFF WRITERS

They kept washing ashore, hundreds of them. The huge but emaciated bodies of gray whales floated lifeless into Puget Sound and San Francisco Bay, and drifted onto beaches from Alaska to Baja.

The putrid carcasses became such a nuisance in 1999 and 2000 that beach communities took to towing the 35-ton cadavers out to sea or burying them with backhoes. Eskimo whalers reported harpooning "stinky" whales that appeared to be rotting alive, too smelly even for dogs to eat.

Although the die-off has stopped--as mysteriously as it began--the most recent tally shows the gray whale population has plunged by more than one-third, falling from an estimated peak of 26,635 whales in 1998 to 17,414 this spring--the lowest in nearly two decades.

"That's a jolting decline for a long-lived species," said Ray Highsmith, a professor of marine science at the University of Alaska at Fairbanks and an expert on the main food source for gray whales. "If the numbers are right, there's something seriously wrong."

For The Record
Los Angeles Times Tuesday June 25, 2002 Home Edition Main News Part A Page 2 National Desk 15 inches; 564 words Type of Material: Correction
Gray whales--An article in Monday's Section A on the decline of the Pacific gray whale misspelled the scientific name of the animal's main source of food, a small crustacean that lives in arctic waters. The correct spelling is Ampelisca macrocephala.
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The die-off was a stunning setback, coming as it did just five years after the whales had been taken off the endangered-species list. The grays, all but extinct in the 1930s, had appeared to be thriving by the mid-1990s.

Particularly troubling has been the inability of scientists to pinpoint the cause. Hunting, the old nemesis, could not be blamed. Only 140 gray whales are taken each year by Eskimo and Native American hunters, the only people allowed to kill the animals.

Exactly what has gone wrong remains a topic of considerable debate. One scientist thought it was the flu. Another blamed chemical pollutants. Others pointed to the cyanide-based fluorescent dye used to mark illegal narcotics drops in the ocean. Was it collisions with boats? Navy sonar experiments exploding whale eardrums? Killer whales with outsized appetites?

Current thinking centers on the whale's food supply. The recovering population of whales simply may have been eating more than nature could provide. At the same time, nature itself, buffeted by global warming and shorter-term climate changes such as El Nino, may have been producing less of the cocktail-shrimp-sized sea-floor amphipods that are the primary food of grays.

"All of a sudden, in 1999, the bottom fell out. We went from 1,400 calves to 420. Strandings jumped from 35 to 270," said Wayne Perryman, a biologist with the Southwest Fisheries Science Center in La Jolla. "That's not a subtle signal."

The casualties didn't just include the sick, weak, young and very old. Many of the dead animals should have been in the prime of their 50-year lifespan.

In the spring of 2000, veterinarian Frances Gulland of Sausalito's Marine Mammal Center conducted full necropsies on three animals and found as many distinct causes of death: viral encephalitis, the biotoxin domoic acid and parasitic abscesses. "All of those could have initially started as malnutrition," Gulland said. "The real question is, why were they so malnourished? Why did they get whatever caused them to die?"

A team of Alaskan biologists is now conducting the first in-depth chemical analysis of fresh samples of gray whale blubber in the hunt for clues.

There has been one common denominator in both the living and dead: Many of the animals were so skinny that their ribs stuck out. The scrawniness was visible from aerial photographs.

As for the medicine-like stink that prompted complaints from Eskimo hunters, Perryman said it could have been a result of a defective metabolism or simply the stench of starvation. "Just like with human beings, their breath is affected by what they're eating," he said. The breath of gray whales might be rancid, he said, because they are breaking down deep energy reserves and protein, instead of burning calories from recently ingested food or their own blubber.

If the whales were starving, what happened to their food?

The 35- to 50-ton beasts spend their summer in the Bering Strait, gorging on millions of amphipods--crustaceans that live in tubes in the mud and sand on the shallow ocean floor. The whales dive for the critters, sucking in mouthfuls of ocean bottom. They strain mud and sand out through baleen, and swallow the amphipods.

Although they can eat other things, studies of whale stomach contents show that one species of amphipod--Ampilesca macroephala--makes up 95% of the whale's Arctic diet. Because whales eat little while migrating or basking in Baja, the blubbery animals must do a year's worth of fattening up on this one species in the few months they spend near the Bering Strait.

Bruce Mate, an expert at Oregon State University and Sea Grant on endangered whales, thinks there isn't enough food because there are too many whales. "Our leading hypothesis is, they actually overshot their food supply," he said.

Mate's "starvation hypothesis" presumes a dark side to the whale's spectacular recovery--that the population can rise only so high before being cruelly adjusted back into equilibrium with nature.

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