Can powerful noises affect whales? There's circumstantial evidence to suggest that they might. Now a team of researchers is attempting to find out for sure.
The notion that at least some species of whales might be adversely affected by loud noises rests on two pillars. First, the cetacean world is one of sound, rather than vision; toothed whales use echolocation to find their way around and locate prey, and several species of baleen whales in particular emit deep vocalizations that can travel hundreds, possibly thousands, of miles across the ocean.
Secondly, there have been more than a few occasions on which whales have beached or been found dead in close proximity to a powerful noise source.
In particular, accusatory fingers have frequently been pointed at military use of powerful active sonar, which has been linked to numerous cases of strandings and death, particularly in various beaked whale species. While few if any of the individual cases can be linked unequivocally to a specific use of sonar, the accumulation of incidents is making a powerful case for the prosecution. Some have theorized that the sound panics the whales, forcing them to flee to the surface too quickly, causing them to suffer from rapid decompression.
But there is still surprisingly little clarity on the precise mechanisms by which sound could impact a cetacean, or even how an external source would propagate inside a cetacean's head – a hole in the knowledge base that a joint US-Swedish team is attempting to fill.
In a recent paper in the online journal PLoS One, scientists from San Diego State University, University of California, San Diego and the Kolmarden Zoo in Sweden developed an approach that "integrates advanced computing, X-ray CT scanners, and modern computational methods that give a 3D simulated look inside the head of a Cuvier's beaked whale" - the species seemingly most affected by active sonar tests.
basic research into the mechanism of sound production and hearing in these whales, simulate exposure at sound pressure levels that would be impossible on live animals, or assess various mitigation strategies,"
says Petr Krysl, of UC San Diego.
It's just the first step in an ongoing effort to understand what goes on - at least on one level - inside a beaked whale's head. It doesn't definitively answer whether Navy sonar is killing cetaceans - yet. But by creating a greater understanding of the pathways by which sound travels inside a whale brain, it may very well help answer that question in the future.
"We believe that our research can enable us to understand, and eventually reduce, the potential negative effects of high-intensity sound on marine organisms," says Krysl.
Image: Jacobs School of Engineering