Reports from around the world say that whales have stranded themselves within miles and hours of navy vessels testing mid-frequency anti-submarine sonar.
Scientists can only offer theories about the impact of tactical sonar. Fish-finding sonars are more prevalent worldwide, but, by contrast, "they're generally at a higher frequency, which doesn't carry as far in water as mid-frequency sounds," said Christopher Clark, director of the bioacoustics research program at Cornell University in Ithaca, New York, who has studied whale communication for 30 years.
Beached Whales and Hemorrhaging Ears
In one stranding incident near the Canary Islands last year, "If you look at where the ships were operating, relative to the whales, it looks like the animals got herded out of the water and driven onto the beach by the sound," Clark said.
"Why the sound terrified them, we don't know. But I've listened to some of these anti-sub sonars and they have a similar effect to the sound of a killer whale. Perhaps the animals fled what they perceived as the threat of a natural predator."
Another possibility is that "the sound causes vibration in [the animals'] ears that leads to hemorrhaging," said Ken Balcomb, a senior researcher at the Center for Whale Research in Friday Harbor, Washington.
Scientists also are aware of the tradeoffs between the environment and a competitive military.
"I think there needs to be oversight of military training, that's clearbut we have to consider what happens to our military if they don't train with these sonars," said Ketten.
"Tactical sonar is essential for national defensethat's not in question," Balcomb said. "The issue is when and where you test it."
Scientists agree on sonar's value for research purposes.
"Sound waves are our most important tool for mapping and exploring the ocean," Ketten said. "But more needs to be done to figure out how to use this technology responsibly."
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