A new study has added the world’s largest creatures ever, blue whales, to the list of undersea animals that are harmed by military sonar off the coast of California.

The Southern California Behavioral Response Study by Cascadia Research tagged 17 of the behemoths with suction cups in 2010 and 2011, then tracked their movements as they responded to audio stimulus. Not all the whales behaved the same, but in general, most of it wasn’t good. Some whales stopped eating, some increased their speed and others fled. They temporarily avoided areas where they heard the sounds and modified their diving behavior.

Blue whales and other baleen whales have broom-like filters in their mouths rather than teeth that they use to collect small, shrimp-like krill as they move through the water. Past studies have shown that some toothed whales subjected to mid-frequency sounds have ended up in lethal mass strandings, but this was the first time baleens were studied.

The study concluded that, “Sonar-induced disruption of feeding and displacement from high-quality prey patches could have significant and previously undocumented impacts on baleen whale foraging ecology, individual fitness and population health.”   

The researchers used mid-frequency sonar sounds that are much less intense than what the U.S. Navy uses on a regular basis. They did their testing off the Southern California coast, where blue whales frequently feed and the military regularly runs training exercises.   

Whales, like other large undersea mammals, are thought to rely on sound communication, sometimes across vast distances, for critical information. Blue whales used to roam the Earth in great numbers, but years of whaling took its toll and only an estimated 10,000 are left on the planet.

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 appears in the July 3 Proceedings of the Royal Society B.     

–Ken Broder

To Learn More:

Military Sonar Can Alter Blue Whale Behavior, Study Finds (by Lance Tillson, National Monitor)

Military Sonar Can Alter Blue Whale Behavior (by Duke University)

Sonar May Pose Risk for Feeding Blue Whales, Researchers Say (by Sandy Mazza, Torrance Daily Breeze)

Coastal Commission Rejects Navy Blasting near Whales, but May Not be Able to Stop It  (by Ken Broder, AllGov California)

Blue Whales Respond to Simulated Mid-Frequency Military Sonar (Cascadia Research Collective)