Endangered Whales May be Affected By Military Sonar Use

A new research report has revealed that military sonar blips may be harming blue whales. The study, conducted by a team of scientists in conjunction with Duke University, found that mid-frequency signals negatively affect the diving behavior of these massive animals.

Sonar blips are routinely used by the military for underwater navigation and communication. The researchers wanted to test the theory that these noises scare whales away from their habitats and damage their hearing, leaving them unable to hear other whale calls. In the past, sonar has been linked to mass stranding of deep diving beaked whales.

This time however, the researchers were testing sonar's effect on blue whales, a type of baleen whale. The team used sonar sounds between 3.5 and 4 kHz, a level considered mid-frequency, but not quite as high as those the military uses. They then attached suction cups to the animals to record their movements.

According to the results, the whales were clearly affected by the noise. They often fled from the noise and left their usual feeding grounds in order to avoid the sonar blips. 

"Whales clearly respond in some conditions by modifying diving behavior and temporarily avoiding areas where sounds were produced," said study author Jeremy Goldbogen of the Cascadia Research Collective. "But overall the responses are complex and depend on a number of interacting factors."

The research team believes that this sonar noise pollution may be a serious threat to the blue whales, a species that is endangered.

"Our results suggest that frequent exposures to mid-frequency anthropogenic sounds may pose significant risks to the recovery rates of endangered blue whale populations, which unlike other baleen whale populations (i.e. humpback, grey and fin whales), have not shown signs of recovery off the western coast of North America in the last 20 years," the study states.

The National Oceanic and Atmospheric Administration reports that there are less than 12,000 blue whales remaining in the world today, with some estimates as low as 5,000.

The study was published in the journal Biology Letters.