Noise from ships has cut the ability of critically-endangered North Atlantic right whales to communicate with each other by about two-thirds.
From 2007 until 2010, scientists led by the NOAA monitored noise levels and recorded the distinctive sounds made by several species of baleen whales, including the 'up-calls' made by right whales to maintain contact with each other.
By comparing noise levels from commercial ships today with the lower levels nearly a half-century ago, and examining the extent to which noise inhibits communication in whales, the authors estimate that right whales have lost 63 to 67 percent of their communication space.
"A good analogy would be a visually impaired person, who relies on hearing to move safely within their community, which is located near a noisy airport," says Leila Hatch, NOAA’s Stellwagen Bank National Marine Sanctuary marine ecologist and lead author of the paper.
"Large whales, such as right whales, rely on their ability to hear far more than their ability to see. Chronic noise is likely reducing their opportunities to gather and share vital information that helps them find food and mates, navigate, avoid predators and take care of their young."
North Atlantic right whales, which live along North America’s east coast from Nova Scotia to Florida, are one of the world’s rarest large animals. Indeed, they're on the brink of extinction, with recent estimates putting the population at just 350 to 550.
"We had already shown that the noise from an individual ship could make it nearly impossible for a right whale to be heard by other whales," says Christopher Clark, director of Cornell’s bioacoustics research program.
"What we’ve shown here is that in today’s ocean off Boston, compared to 40 or 50 years ago, the cumulative noise from all the shipping traffic is making it difficult for all the right whales in the area to hear each other most of the time, not just once in a while. Basically, the whales off Boston now find themselves living in a world full of our acoustic smog."