In 2005, NRDC filed a lawsuit contending that the use of active, submarine-hunting sonar posed threats to cetaceans and violated, among other laws, the Marine Mammal Protection Act, the National Environmental Policy Act and the Endangered Species Act. Although a Los Angeles federal court agreed, and ordered the Navy to enact a number of safety measures to protect whales, Navy officials appealed to the Supreme Court, which in 2008 overturned two of six mitigation measures while leaving the rest in place.
Meanwhile, research into the impact of active sonar on cetaceans continues – including, to its credit, by the Navy. Indeed, the Navy participated in new research that has provided the first concrete evidence that sonar does indeed affect behavior in at least one cetacean species.
Writing in the online journal PLoS One, Peter Tyack of the Woods Hole Oceanographic Institution and colleagues describe a study at the Atlantic Undersea Test and Evaluation Center in the Bahamas, in which they deployed underwater microphones to listen for the "click trains" emitted by Blainville's beaked whales using echolocation to find their prey: