Underwater cacophony is latest threat to belugas

08/20/2002
National Post

Scientists have begun a major study to find out whether beluga whales in the St. Lawrence River are suffering from noise levels that can be so high, the mammals must repeat themselves to be heard.

Federal scientists are mapping the sound levels experienced by the animals, fearing the constant din of whale-watching boats and commercial freighters might cause permanent damage.

Belugas have been nicknamed canaries of the sea because of their frequent vocalization. Experts say even partial deafness could be catastrophic as hearing is their primary sense in a murky world.

The St. Lawrence estuary is home to a dwindling population of about 500 of the animals, decimated by whaling in the past and more recently by pollution spewed by surrounding industry.

Previous research has shown that when boats pass nearby, the belugas behave much like people in a bar with loud music, said Véronique Lesage, a Department of Fisheries and Oceans scientist.

"They start to repeat themselves, and then yell and then move to higher frequencies to avoid the band where the noise is louder," she said.

"And, at some point, they just shut up and say, 'Let's talk later,' I guess."

The St. Lawrence's beluga population was declared endangered in 1983. Some of the chemical waste in the river has been eliminated, but the effects of contamination are still being found, with many belugas suffering cancerous tumours and impairment of their immune and reproductive systems.

Research begun in the early 1990s points to another possible hazard. Tests using underwater microphones suggest noise in parts of the belugas' St. Lawrence habitat is loud enough that it would cause temporary or permanent damage to hearing in a human, concluded Peter Scheifele, a researcher from the University of Connecticut.

Mr. Scheifele said beluga ears are sufficiently similar to those of people to apply the same noise safety standards.

The Fisheries and Oceans study now seeks to determine more definitively whether the whales are facing perilously high levels of sound.

The goal is to attach instruments, including a hydrophone (a waterproof microphone) on the backs of belugas with suction cups fired from crossbows. The instruments would track the movements of the whales, the sounds they make and hear, and their response to the noise around them, Ms. Lesage said.

Technical difficulties have delayed that part of the experiments until next year at the earliest but, in the meantime, researchers have begun mapping exactly where the whales live and swim in the estuary. That information will be matched with data on the noise underwater to determine indirectly where belugas encounter loud noise, said Robert Michaud, scientific director of the independent Group for Research and Education on Marine Mammals, which is taking part in the federal study.

"If you live in a three-dimensional world where sound is the first means of communication, being deaf at some specific frequency could be catastrophic," he said.

"Essentially, they are sensing their world through sounds."

The many whale-watching boats that ply the mouth of the St. Lawrence could be the main culprits. Ms. Lesage said their low-frequency motors tend to produce sound in the range used by the whales to communicate.

As well, the belugas' summer range overlaps a major shipping lane for freighters entering the Great Lakes from the Atlantic.

Ms. Lesage said new regulations might be necessary, but the research will not be completed for about three years.

Whale-watching boats already have to stay 400 metres away from belugas.

Critics of whale-watching tours off of Vancouver Island have also raised concerns about noise pollution there.