Christopher Clark: Whales off Newfoundland can hear whales near Bermuda Print E-mail
Written by David Brand   
Thursday, 24 February 2005 00:00

Source: http://www.news.cornell.edu/Chronicle/05/2.24.05/AAAS.Clark.whales.html

It is an irony that just as researchers are gaining new ways of understanding the linkages between whales and oceanographic features by listening to their songs, what is being heard is a rising tide of "ocean smog"-- the collective noises from shipping traffic, oil and gas exploration and production, and recreational traffic. And every decade the amount of noise is doubling.

Christopher Clark, Cornell's I.P. Johnson Director of the Bioacoustics Research Program, sits with one of the autonomous sea floor recorders in the bioacoustics fabrication facility in the Lab of Ornithology Feb. 16. Clark uses the underwater microphones, which were initially developed to track Soviet submarines, to chart undersea whale songs. He discussed his research at the AAAS annual meeting Feb. 19 and 20. Frank DiMeo/University Photography

For nearly nine years Cornell researcher Christopher Clark -- together with former U.S. Navy acoustics experts Chuck Gagnon and Paula Loveday -- has been trying to answer these questions by listening to whale songs and calls in the North Atlantic using the navy's antisubmarine listening system. Instead of being used to track Soviet subs as they move through the Atlantic, the underwater microphones of the Sound Surveillance System (SOSUS) can track singing blue, fin, humpback and minke whales.

Clark, the I.P. Johnson Director of the Bioacoustics Research Program, discussed his research into the rich acoustical environment of whales at a news briefing at the American Association for the Advancement of Science (AAAS) Feb. 19. He also described his research in an AAAS seminar Feb. 20.

"Many whales have very traditional feeding grounds and their migratory routes occur along shallow coastlines, which are now some of the noisiest, most heavily impacted habitats," Clark said. But often it is along these routes that the male songs are sent long distance to prospective females, who might not receive the message through the "ocean smog."

Said Clark, "If females can no longer hear the singing males through the smog, they lose breeding opportunities and choices. The ocean area over which a whale can communicate and listen today has shriveled down to a small fraction of what it was less than a century ago."

From the acoustical maps he and his colleagues have obtained, Clark has come to realize that he has been thinking about whales at the wrong time scale. "There is a time delay in the water, and the response times for their communication are not the same as ours. Suddenly you realize that their behavior is defined not by my scale, or any other whale researcher's scale, but by a whale's sense of scale -- ocean-basin sized," he says.

"We know very little about whale communications. That is why we are looking for patterns of association and coordination. The problem is that the whales are spaced so far apart," said Clark. However, the SOSUS system is providing a wealth of new data. In weeklong soundings at the U.S. Navy's Joint Maritime Facility in St. Mawgan, Cornwall, England, Clark has obtained thousands of acoustical tracks of singing whales for the different species throughout the year. "We now have the ability to fully evaluate where they are and how long they sing for," he said. "We now have evidence that they are communicating with each other over thousands of miles of ocean. Singing is part of their social system and community."

Using SOSUS, Clark can move a cursor around a screen and listen in on different areas of the North Atlantic. If he hears a whale singing, he can fix its location and position it in space and time and observe animals that are many tens of miles apart -- cohorts of humpback singers moving coherently -- and watch the collective migration of species in large portions of the ocean basin. "So if I am a whale off Newfoundland, I can hear a whale off Bermuda," said Clark. "Whales will aim directly at a seamount that is 300 miles away, then once they reach it, change course and head to a new feature. It is as if they are slaloming from one geographic feature to the next. They must have acoustic memories analogous to our visual memories," he said.

 
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