Boats drown out sound of whales

Noise: As more vessels take to the water with whale-watching tourists, the sea creatures are forced to adjust to the manmade din.

Medicine & Science

May 03, 2004|By Dennis O'Brien | Dennis O'Brien,SUN STAFF

So many whale-watching boats are plying popular waterways that the whales are having trouble being heard over the din.

Researchers say that "calls" made by killer whales in the Pacific Northwest are about 15 percent longer than they were in 1990, when whale watching began to take off.

The scientists say that, like humans, the whales are trying to adjust to the noise around them.

"If you're at a cocktail party, you start talking in a louder tone if the noise level goes up. It's the same thing," said Richard W. Osborne, an expert on killer whales at the Whale Museum on Washington's San Juan Island.

Researchers examined calls made by about 80 extensively studied killer whales that arrive to feed on salmon every summer in Haro Strait, about 100 miles north of Seattle.

They compared underwater recordings of killer whale calls made in the presence and in the absence of boats between 1977 and 1981, between 1989 and 1992, and between 2001 and 2003.

They found that the calls become longer after whale-watching boats increased in the area. The number of whale-watching trips has increased fivefold since the early 1990s, to about 22 boats a day.

The authors note that killer whales aren't the only animals that have to adjust to be heard over the hum of human activity. Previous studies have found humpback whales and certain species of birds are also singing longer and at higher pitches.

"It's only in recent years, when the level of human activity increased, that this effect has become noticeable," said A. Rus Hoelzel of the University of Durham in England.

The researchers recommend that whale-watching crews keep their distance from the animals, use the quietest engines possible and slow down to an idle whenever whales are nearby.

Whale-watching tour operators say the findings don't surprise them, but they say many species of whales seem to welcome human company.

"It certainly doesn't seem to bother these whales at all. The whales will come right up to the boat," said Capt. Robert Avila, who offers four-hour whale-watching trips off Massachusetts as a skipper at Capt. John Boats in Plymouth.

Spawned in part by movies such as Free Willy, whale watching has become a major business in many coastal areas. In Massachusetts, whale watching generates about $15 million a year, Avila said.

Avila said school groups come from as far away as Montana and Florida to board boats for the 20-mile trip from Plymouth to the ocean feeding grounds of humpbacks and finbacks.

He said that he and other whale-watching skippers do what they can to keep the boat noise to a minimum, idling engines when the whales are in the area.

Killer whales travel in families, speak in dialects that differ from one group or "pod" to the next, and vary in their diet.

The whales in the study released last week feed almost exclusively on salmon, and scientists believe they use their calls to communicate as they forage.

Other "transient" populations of killer whales feed on dolphins, porpoises and other marine life and hunt in silence, possibly to keep from tipping off their larger prey.

"Sound is everything to these animals. They live in a world of sound the way we live in a world of sight," said Iain Kerr, a whale researcher at Oceans Alliance, a nonprofit research organization.

The Natural Resources Defense Council is suing the Navy to prevent deployment of an ultra-low frequency sonar system designed to detect enemy ships and hazards. The technology "has the potential to harm and even kill whales," said Cara Horowitz, a lawyer for the environmental group.

The Navy disputes the NRDC's claims.

Scientists agree that with increased shipping traffic worldwide, the planet's waterways are becoming noisier places.

Noting a 50-year increase in ocean noise, a report last year by the National Research Council recommended federal oversight of ocean sound levels and long-term monitoring to track the effects of sound levels on marine habitats.

"There's a lot of evidence that the oceans are becoming noisier places," said David Mellinger, an expert on marine mammal acoustics at the Scripps Institution of Oceanography.

But scientists say that there is much to be learned about whether increased noise poses health risks for whales and other marine life.

"If you and I are outside on a windy day and we have to talk louder because of the wind, that doesn't mean it's affecting our stress levels or our reproductive system or immune system," Kerr said.

Hear the whales

Want to hear the killer whale's call? Visit www.baltimoresun.com/whales

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