(CBS Seattle) — Scientists may have found a link between the dwindling blue whale population and U.S. military sonar noise.
A team of scientists recently exposed a group of blue whales in the Pacific Ocean to sonar sounds between 3.5 and 4 kHz that were not as loud as the kind the military uses, according to The Washington Post. In the study, the whales were tagged with suction cups that recorded acoustic data and movements as the animals were exposed to the controlled sounds.
Data later revealed some of the whales avoided their feeding grounds and fled from the source of the noise.
According to researchers, mid-frequency sonar signals (between 1 kHz and 10 kHz) have been blamed for mass strandings of deep-diving beaked whales. There are fewer cases of sonar-linked strandings of blue whales and other baleen whales.
Previous studies on other whales have shown sonar blips that the U.S. military uses in underwater navigation, object-detection and communication can sometimes mask or distort whale calls and alter their feeding habits. In some cases, the sonar noise can damage the animals’ hearing, according to researchers.
“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 researchers wrote.
Military sonar use has sparked heated debates in the Puget Sound region because of the area’s Orca population. In May of 2012 The Kitsap Sun reported environmental groups from both Washington and British Columbia pushed for a ban on sonar use in the inland waters on both sides of the border — including Puget Sound, Georgia Strait and the Strait of Juan de Fuca. The two groups cited several incidents affecting whale behavior. In one instance, a three-year-old female Orca died from unusual trauma and washed ashore in Long Beach, representing a major reproductive loss to the endangered Southern Resident population.
In 2002, the National Oceanic and Atmospheric Administration reported there being between 5,000 and 12,000 blue whales in existance.
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