- 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
- "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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