Stranded: a whale of a mystery: scientists generally agree that sonar can trigger strandings of certain whales, but no one really knows what leads these deep divers to the beach

Science News, July 19, 2008 by Rachel Ehrenberg

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Off the eastern edge of Andros Island lies the Tongue of the Ocean, a hundred-mile, inky blue swathe of sea over the Great Bahama Canyon. Bounded on the south and east by the shallow sands of the Bahamas banks, the seafloor drops precipitously from 3 meters near shore to more than 2,000 meters farther out.

While the region boasts a colorful history of pirates and shipwrecks, scientists will head there this summer seeking treasure of a different sort: beaked whales, some of the deepest diving and least known animals on Earth. The research aims to solve one of the most contentious mysteries in marine biology today- the relationship between military sonar and stranded, dying whales.

In recent decades, a string of whale strandings have coincided with military testing that uses mid-frequency sonar to detect the low murmur of diesel and nuclear submarines. Beaked whales have washed up on the beach, sometimes with blood in their ears and eyes, but often with no obvious cause of death. After scientists first drew the connection between sonar and the strandings, environmental groups took note, embarking on a campaign to restrict sonar use in certain times and places. The hostilities reached a crescendo this winter in a U.S. federal court. A judge rejected the Bush administration's attempts to override a ruling that ordered the Navy to take measures to protect marine mammals while conducting sonar exercises. Now the Supreme Court is scheduled to hear the Navy's appeal this fall.

The wrangling over the stranded whales brings home how science can get lost in the scuffle between advocacy and policy. It also illustrates the highly charged nature of issues involving large, charismatic mammals. And then there's the attraction of simplicity--the Navy makes a tidy, singular foe. But there is no Moby Dick in this story.

Scientists agree that under certain conditions, sonar does trigger strandings of certain whales. But no one really knows why. Hypotheses, like fish in the sea, are plentiful. Sonar may be so forceful that it damages the whales' ears. Some researchers speculate that the sounds spur bubble formation in tissue, bringing on deadly embolisms. Or the sonar might distress and disorient the creatures, prompting them to surface too quickly and get the bends. Other researchers have suggested that certain frequencies of sonar might sound like killer whales on the hunt, stimulating beaked whales to seek shallower, safer waters.

Several research groups are trying to untangle what is happening, with the hope of developing strategies that minimize harm to marine life.

The National Oceanographic and Atmospheric Administration Marine Fisheries Service is partnering with the Navy to undertake some of the first controlled behavior experiments with beaked whales at a Navy Atlantic test center in the Tongue of the Ocean. Others are constructing computer models, looking at CT scans and studying beaked whale anatomy. There are efforts to compile stranding-related information in public databases.

In the meantime, providing policymakers and the public with advice on how to alleviate the problem has been stymied by holes in the data big enough to swim a whale through. Ziphius cavirostris, or Cuvier's beaked whales--the animals most associated with the unusual strandings--are understudied, elusive creatures. They spend little time in surface waters and, until the strandings, people rarely saw these whales at all. Then there are ethical and practical concerns with experiments that involve 2 1/2-ton mammals that spend much of their time nearly a mile beneath the surface of the sea.

The mystery is compounded by several factors. No one knows where the whales are before they strand, so assigning safe distances from sonar is problematic. The strandings have been associated with specific geologic features, such as deep oceanic trenches near land, but by definition, stranded whales end up near or on land, so teasing out cause and effect is difficult. Because no one knows where and when a stranding will happen, experts might not arrive on the scene until days after the event. By then tissues are often decomposed, as are clues to the animal's death.

"One of the problems is we've really only had information on single exposures one sound, one mammal," says Brandon Southall of the NOAA Fisheries Service, who is leading the Bahamas study. "We really need more data."

Some environmental groups and scientists argue that waiting for such data is folly. It is better to act quickly--perhaps by banning Navy sonar altogether--than it is to wait. But others express frustration at the bulldog approach, and at the time and money tied up in lawsuits that might be better spent on research. And while blame is slung in the courts, marine mammals face many threats beyond sonar.

"It is absolutely critical that we understand what is going on," says Darlene Ketten, a senior scientist at the Woods Hole Oceanographic Institution in Massachusetts and a researcher at Harvard Medical School in Boston. "But when people ask, 'Why don't you shut down the Navy?' the answer is we're talking about five animals a year, and I have to balance that with over 100,000 deaths a year from fisheries interactions. I don't know that shutting down the Navy is going to do anything. And if you are worrying about noise in the oceans, how about the 3-decibel increase per decade from shipping?"