A groundbreaking series of studies measuring whale responses to underwater sonar proves what has long been suspected: Sonar seriously spooks whales.
Although researchers have known that sonar and ocean noise can interfere with dolphins’ and whales’ sonarlike navigation system –echolocation –research by Southern California Behavioral Response Studies proves for the first time that midfrequency sonar, like that used by military training exercises worldwide, causes life-threatening reactions by whales.
Scientists exposed toothed and baleen whales to midfrequency sonar well below the level used by the U.S. Navy. While scientists expected deep-diving toothed whales to react –beaked whales are the most common species associated with sonar-implicated strandings –the blue-whale responses were unexpected. Blue whales, previously thought insensitive to midfrequency sonar, stopped eating and fled form their foraging habitat when the sonar began. The study’s authors say this response behavior could put survival of the species at risk. According to lead researcher Stacy DeRuiter of University of St. Andrews, Scotland, whales “responded to simulated sonar with strong, consistent and sustained avoidance.”
Some of the whales made unusually long and deep dives, behaved erratically, and went silent –behaviors that lead to mass strandings. “This result has to be taken into consideration by regulators and those planning naval exercises,” says DeRuiter.