Study Implicates Naval Sonar to Changing Whale Behavior

A study funded by the United States Navy illustrates how noises from explosives, engines and other industrial activities can directly affect blue whale (Balaenoptera musculus) behavior.

The largest marine mammal, with most adults over 100 feet long and 30 tons in weight, has been the target of studies like this for years but in this newest experiment, researchers found that sonar-induced disruptions on how whales feed could have previously undocumented impacts on their health. 

To conduct the experiment, researchers simulated military sonar adn other mid-frequency sounds on tagged blue whales in feeding areas within the Southern California Bight. Within the controlled areas, researchers then exposed the whales to two different sounds: simulated military sonar signals and "pseudo-random noise". 

What they found was that whales in certain states, such as feeding or non-feeding, were ultimately affected by the noises. Researchers described their actions as "brief avoidance responses" and when the noises were deactivated, the whales' behavior tended to return to pre-exposure conditions. 

A leading hypothesis amongst whale researchers is that acoustic sonar waves may disrupt communication between blue whales, leading to mass strandings. These events have been documented since 1874 but since the introduction of naval sonar, the frequency of whale strandings has increased over time. 

Researchers concluded that the behavioral changes due to naval sonar operations hinges on the amount of noise the whale is exposed to and whether or not the whale was feeding.