New research from Duke University looks at how whales are impacted by military sonar used in underwater training exercises. The study was conducted off the coast of California and found that whales might avoid important feeding sites when exposed to mid-frequency sonar routinely produced at a nearby military training site.
"Whales clearly respond in some conditions by modifying diving behavior and temporarily avoiding areas where sounds were produced,” said lead author Jeremy Goldbogen in a statement released by Duke. "But overall the responses are complex and depend on a number of interacting factors," such as the depth of the whales and whether or not they are feeding at the time.
Military sonar has been associated with marine mammal strandings in the past, but this study is the first to provide evidence of how blue whales react to the frequencies.
"Blue whales are the largest animals that have ever lived. Populations globally remain at a fraction of their former numbers prior to whaling, and they appear regularly off the southern California coast, where they feed," said John Calambokidis, one of the project’s lead investigators, in a statement from Duke.
The research team also published a related study that shows even stronger responses to sonar from Cuvier’s beaked whales, a smaller, more common whale species.
The study was funded by the U.S. Navy Chief of Naval Operations Environmental Readiness Division and the U.S. Office of Naval Research. It was published July 3rd in the Proceedings of the Royal Society B.