HONOLULU — A new study offers evidence to support the theory that beaked whales get the bends when they surface rapidly, possibly after being startled by naval sonar.
The report could help scientists understand why beaked whales appear to be more vulnerable to the potentially harmful effects of sonar than other marine mammals.
Together with other studies, the results may also help scientists and regulators think of how navies could adjust their sonar use during training to prevent beaked whale strandings and deaths.
“It provides more evidence that beaked whales that are being found dead in association with naval sonar activities are likely to be getting decompression sickness,” said Robin Baird, a marine biologist at Cascadia Research Collective and one of the report’s authors.
The study, published online this week in the journal Respiratory Physiology and Neurobiology, uses data gathered from three species in the beaked whale family. Two of the species, Cuvier’s and Blainville’s, were observed in Hawaii waters. The third, northern bottlenose whales, were studied off Nova Scotia, Canada.
Military ships use mid-frequency active sonar by firing bursts of sound through the water and listening for an echo off a vessel’s hull.
The technology has become increasingly important to the U.S. Navy as other countries, including China, have added quieter, harder-to-detect diesel-powered submarines to their fleets.
In 2000, several beaked whales washed ashore with bleeding around their brains and ears during Navy exercises in the Bahamas.
Scientists believe the bleeding may have been caused by bubbles that formed in the whales’ bloodstreams when they surfaced more quickly than normal.
The Navy has since agreed to adopt some measures to protect whales, such as having ships turn off their sonar when sailors spot marine mammals nearby.
But it has strongly resisted many more stringent restrictions, saying there isn’t enough scientific evidence to require them.
The Navy is also pushing for more research in the area, budgeting $26 million annually over the next five years to understand how marine mammals hear and how sound affects them.
The new beaked whale study was also funded in part by the Office of Naval Research.