Whales Respond To Navy Sonar
By Dana Warn
Singing humpback whales respond to Navy Low Frequency Active sonar by clamming up or belting out longer tunes, new research suggests.
The study, led by Peter Tyack of the Woods Hole Oceanographic Institution' is the first published in a series of investigations to determine the effects of the Low Frequency Active sonar that the Navy has been testing to detect stealth submarines.
The sonar is under review due to concerns that it may harm marine life. These worries have increased recently since an investigation suggested that sonar may been a factor behind the beaching of 16 whales in the Bahamas in March.
"The whales, reaction was subtle and short-lived, says Kurt Fristrup, Assistant Director of the Bioacoustics Research Program at Cornell, and a participant in the Navy-funded Low Frequency Sound Science Research Program, who commented on Tyack's study.
David Ellifrit, Center for Whale Research, examines a dead whale beached on Abaco Island. (Diane Claridge/AP Photo)
Fristrup says the team designed the research program to see how the most sensitive animals would react to close encounters with the sonar. The LFA sonar system was developed in 1988 to detect increasingly quiet submarines. Although active sonar has been used since World War II, this system is unique because of the low frequency that allows the Navy to detect submarines over ranges more than five times as large as other systems Fristrup reports that they found little evidence that the LFA sonar harmed baleen whales. But Joel Reynolds, an attorney for the Natural Resources Defense Council, says the research does not address chronic effects. He says the research focus was driven by the Navy's desire to meet a predetermined deployment schedule for the sonar.
Complex Songs
Scientists still don't understand the full meaning behind the complex and flexible songs of baleen whales, massive mammals that capture their food with large plates, rather than teeth. Louis Herman' a scientist from the University of Hawaii, has studied humpbacks " a kind of baleen whale " for 25 years and says the long, haunting tunes are linked to the whales, breeding. Although whales are rarely seen mating, humpbacks sing in the winter and reproduce in the same season' he says. Some scientists suspect that male whales sing to compete with other males, while others even suggest the whales may be using the songs as sonar. To design the research, part of which appeared this week in the journal, Nature, the research team posed a simple question. "We just asked: How could a loud sound affect a whale? Fristrup says. "And how could you detect the effect? Scientists followed singing humpback whales, monitored their behavior, and then watched for changes in their behavior after the Navy turned on its sonar.
"We tried to get as close to the whales as possible, says Joe Johnson' the program manager for the Navy's LFA sonar Environmental Impact Statement, who drove the ship that carried the sonar.
Subtle Effects
The scientists found that during sonar transmissions, the whales that kept singing had 29 percent longer songs, while some of the whales stopped singing. The effects appeared to go away an hour after the sonar transmission finished. Due to the close observation of the whales, the study only looked at 16 singers.
"While there could be subtle effects we haven't seen' the measured effect goes away, suggesting there are not lasting difficulties [for the whales], Fristrup says.
Others are more concerned. "Singing comes at a cost...and longer songs are presumably more costly, says Lindy Weilgart, a researcher who studies sperm whales at Dalhousie University in Nova Scotia, Canada. "How much this would interfere with mating is unknown' she says, "but it certainly isn't likely to be a beneficial effect.
The results may seem promising, but others point out that the study's test group was narrow. The research program focused only on baleen whales, since these massive mammals broadcast sound in the same frequency range as the sonar and have ears specialized for low frequency hearing. They also travel broadly, increasing their likelihood of encountering the sonar.
"We are concerned about the focus on one type of whale, Reynolds says. Reynolds also says that the sonar levels the scientists used for the studies were relatively low. He says that the Navy may use the sonar at levels a million times stronger.
For The Long Haul
This recent study is only one part of a broader research program designed to study how low frequency sonar affects the migration' feeding, and breeding of baleen whales.
Forthcoming studies will analyze effects of the sonar over two time frames: immediate and 20-day periods. The slightly longer studies allow researchers to monitor larger numbers of whales. But the implications these studies may have for exposure beyond 20 days remains unclear. "We cannot extrapolate long-term consequences on the entire marine environment from short-term studies on individuals, Weilgart says. The earliest possible deployment of the Navy LFA sonar system would be this fall, after the final assessment is released.
Reynolds argues that scientists still know too little to begin using the sonar. "Too little is known to justify global deployment, he says. "The [assessment] will need serious revisions.
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