A naval exercise off the Australian coast using submarine-hunting sonar could kill whales or cause them to become stranded, the International Whaling Commission warned in a report.
Environmental groups say the mid-frequency sonar U.S. and Australian forces plan to use can cause hearing loss and tissue damage in whales and can alter their diving habits. Deep-diving species such as the beaked whale are especially at risk, they say, because rapid surfacing can result in the bends, a decompression sickness that can be fatal.
"The reality is the strandings are only the tip of the iceberg," said Marsha Green of the Ocean Mammal Institute. "Most of the animals that are injured are going to die and sink to the bottom."
The biennial exercise, from June 19 to July 2, will be held off the Australian coast near Queensland and the Northern Territory. More than 20,000 U.S. and 7,500 Australian troops are expected to take part. The exercise will include 125 aircraft and 30 vessels, officials said.
"This is an area where there are beaked whales, and beaked whales have been sensitive to mid-frequency sonar," IWC scientific committee chairman Arne Bjorge told The Associated Press at the group's annual meeting, held in Anchorage last week.
Few beaked whale strandings have been documented in Queensland. But there have been incidents elsewhere, including one in 2002 in the Canary Islands, where 15 beaked whales were stranded after a NATO exercise.
Scientists found bleeding around the animals' brains and ears and lesions in their livers and kidneys. They suspected sonar was to blame.
"Post-mortem examination of beaked whales there found clear indications of significant trauma from the mid-frequency sonar," Bjorge said.
In 2000, naval sonar also contributed to 16 whales and two dolphins being beached in the Bahamas, according to a National Oceanic and Atmospheric Administration study.
Lt. Steve Curry of the U.S. Navy's Seventh Fleet said by e-mail the Navy would do everything it can to prevent whale fatalities.
"The Navy is committed to the continued use of active sonar and goes to great lengths to minimize any potential effects on marine life through the use of protective measures," he wrote.
Australian navy officials did not return phone calls seeking comment.
Donna Petrachenko, Australia's commissioner to the IWC, said her government had made sufficient plans to avoid a crisis. They include monitoring beaches and having a response team ready, according to an IWC report. Sonar levels also will be limited to less than 230 decibels and the military will be required to visually search surrounding waters for whales before operating sonar.
Michael Castellini, a University of Alaska Fairbanks marine biologist, said some evidence indicates certain beached whales have developed the bends, but current data can't prove sonar is the cause.
Other research indicates the sound waves themselves can cause tissue damage, he said. Different tissues vibrate at different frequencies, so they can shear where they touch, he said.