Science / Medicine : A New Era for Whale Study : Researchers Discover How the Environment Affects Seasonal Migration

Lugging an old-fashioned crossbow, Steven Swartz stepped aboard ship and set out to sea in search of ancient quarry--the Pacific gray whale.

But the recent expeditions of his scientific research boat were aimed at unraveling mysteries, not at slaughter. For two seasons, concluding last year, he has fired arrows into the thick blubber of whales traveling south along the California coast, implanting tiny radio transmitters.

He then used the transmitters to track the whales as they moved toward their winter breeding grounds off the coast of Baja California, expecting to confirm age-old beliefs about their migration routes.

“We all had this preconception that the animals moved on through in an orderly fashion and just kept going,” Swartz said.

But instead, the ambitious study found surprises about a creature whose 10,000-mile yearly migration is considered the longest in the mammal world. Some whales did in fact swim directly to Mexico. Others spent days near the Channel Islands. A number of females even used the islands to breed, giving birth to 35 calves in the four days that scientists watched them.

“It was just an eye-opener for everyone,” said Swartz, a former private research consultant who now works for the Center for Environmental Education in Washington.

Effects of Man

These are splashy times for whale research. As the gray whale makes a dramatic recovery from near extinction, scientists are researching questions about how they live and how they are affected by man.

Since the late 1930s, when slaughter by man reduced their numbers to few hundred, gray whales have rebounded to about 18,000, scientists believe. Now, during the migration season--which runs from the last week in December to the first week in April in Southern California--scientists from the National Marine Mammal Laboratory are taking a detailed count of the passing parade.

If the $40,000 census finds the population to have reached pre-slaughter levels of 20,000 or more, gray whales ultimately could be removed from the federal endangered species list, oceanographer Marilyn Dahlheim predicted.

At the same time, other scientists are furthering their research into key questions about the effects of whale-watching boats, offshore oil-drilling rigs and commercial gill-net fishermen on whale behavior. That work has extended from the summer feeding grounds in Alaska all the way to the placid breeding lagoons of Baja California, and often has raised as many questions as it has answered.

A few years ago, for example, scientists noticed an apparent shift in migratory routes as whales seemed to be traveling several miles farther offshore.

“That has led people to wonder why,” said Steve Cooper of the Oceanic Society Expeditions office in San Francisco. “People are looking at pollutants in the water. Boat traffic is a possibility. . . . Or it might be something cyclical that’s been going on for thousands of years and we’re just now becoming aware of it. Nobody knows.”

The American Cetacean Society, a nonprofit group devoted to whale studies, is now deep into a long-range effort to answer that question, expanding on Swartz’s earlier transmitter research. The society has placed observers on the Palos Verdes Peninsula, Santa Catalina Island and other islands.

“North of Point Conception, the animals tend to stay close to shore,” said marine biologist Tom Lewis, vice president of the organization. “But when they hit Point Conception they tend to fan out. Some go out as far as San Nicholas Island, 70 miles offshore. Some stay close to shore. At this point, we really do not know much about how the animals travel through the Channel Islands.”

If scientists can pinpoint where the whales go and how they react to boats and drilling rigs, it may become easier to prevent future damage to whale populations, Lewis said. One finding has been that whales like relatively shallow water of 600 feet or less. That keeps them within a few miles of shore or close to the islands when traveling south. Northbound whales, especially mothers and newborn calves, almost invariably cling to the coastline.

Few of the 45-foot mammals are ever found in the deeper channels between islands, Lewis said.

In addition, southbound whales traveling through the Channel Islands almost always seek the west coastline. Occasionally, scientists have seen whales start to pass down the east, or front, side of an island. “But 99% of those animals go a mile or two down the front side, turn around and go back to the back side,” Lewis said. He speculated that southbound whales “want to keep land on their left.”

So far, however, researchers are still unsure whether migration routes have really shifted, or whether such a shift would signal a danger to the whales. Many scientists are concerned, Lewis said, that whale watching, a multimillion-dollar business in California, has created so much motorboat traffic and noise that whales are taking evasive action.

Risk from Sharks

If so, whales and their newborn calves may face greater risk of attack from killer whales and sharks, Lewis said. He also questioned whether some gray whales have the stamina to swim longer, deeper-ocean routes, since they have been found to eat little on the long migratory journey.

“By altering their paths, they may be forced to use more energy,” Lewis said, “and they may have less energy to put into rearing their young. The energy budget of these animals is pretty tight.”

Other experts disagree. Dean Wilkinson, head of the national whale preservation campaign for Greenpeace, said a shift of 10 miles or so in migration routes should mean nothing to a creature covering almost half a globe. “A deviation of 10 miles offshore . . . and you’re talking about less than one degree,” Wilkinson said. “I can’t see that it would have an impact.”

Jonathan Stern, an ecologist at San Francisco State University, is now completing an energetics study of the minke whale, a smaller Pacific species, that he hopes will help answer the question for gray whales. The findings will probably show that whales eat what they must to sustain their migrations, Stern said.

But other concerns about shifting migratory routes have yet to be explored, he said. Newborn calves, for example, may need the quieter waters near shore to rest even if the adult whales do not. Also, scientists do not know whether whales could lose their bearings by shifting their routes, because no one knows whether they travel by following landmarks or whether they simply follow each other.

Scientists agree they have far to go to fully understand the species. The gray whale, the eighth-largest of the whales, lives for 50 years, but it spends 80% of its time under water. That, its size and the fact that males cannot be visually discriminated from females have all made research difficult, scholars say.

Over the years a miscellaneous collection of facts has been accumulated. Whales are known to gorge themselves during the summer months in Alaskan waters, sucking up chunks of the sea floor for small crustaceans. Once the migration begins, they eat less often, burning off nearly a quarter of their body weight.

While migrating, they engage in mating rituals that usually involve two males and a female. After a gestation period of about a year, a newborn arrives measuring 15 feet and weighing close to a ton.

Oceanographer Dahlheim of the National Marine Mammals Laboratory in Seattle undertook a study several years ago to examine one element of the complex whale society--how they communicate and react to sound. When she played motorboat sounds through an underwater speaker, Dahlheim found, gray whales made their own bong-bonging noises more loudly, as though trying to talk over the din.

Different Reactions

When she played the low thudding noise of a drilling rig, whales were less vocal. “It was like they were passively listening,” Dahlheim said. And when she played the sounds of a killer whale--absolute silence.

A year ago, researcher Bernd Wursig of San Jose State University released findings from three years of studies in Alaska that went even further. Wursig’s federally sponsored project in the summer feeding grounds discovered that whales reacted to the sonar of oil-research vessels at distances up to six miles. They even stopped feeding at distances of three-tenths of a mile from some ships.

The findings underscore the importance of safeguarding habitats while extensive oil exploration continues in the Bering Sea, according to Wursig.

Gray whales have been found to be surprisingly gentle, even playful, creatures. Occasional reports of gray whales capsizing small vessels are considered aberrations, and may be nothing more than fish stories.

Marine biologist Lynn Howard recalled a time when she was on a small skiff that got between a mother gray whale and her calf. The mother whale quietly surfaced.

“It was like a big gray wall coming up between the boat and the calf,” Howard remembered. “The mother very gently pushed us away and pushed the baby away, and they took off together. You could feel the power.”

MIGRATION PATTERN OF WHALES

Southbound California gray whales migrate to Baja California for annual Winter breeding December through early April. Their migration routes tend to be closer to the coastline than Northbound whales.

Whales migrate in the Spring as far north as the Bering Sea for annual Summer feeding June through October. Their migration route tends to stray farther from the coastline.