Ship Noise Cuts Whale Communication on Food, Predators, Mates

A new study that focuses on the decrease in whale communication and claims that high levels of background noise produced by ships has greatly hampered the ability of the North Atlantic right whales to communicate with each other.

According to the paper led by NOAA, North Atlantic whales that dwell along North America's east coast from Nova Scotia to Florida are the world's rarest large animals on the verge of being extinct. It is being estimated that the population of North Atlantic right whales are approximately 350 to 550.

Researchers have monitored noise levels across the Stellwagen Bank National Marine Sanctuary from 2007 to 2010. For this they used array of acoustic recorders that also measured the levels of sounds associated with vessels, along with the distinctive sounds made by multiple species of endangered baleen whales. They also monitored the up calls made by right whales to maintain contact with each other.

More than 22,000 right whale contact calls were monitored by NOAA Northeast Fisheries Science Center in 2008. For this study they used the software designed by Cornell and Marine Acoustics Inc. that was helped them in tracking ship noise propagation throughout the study area.

In order to calculate the noise from vessels inside and outside the sanctuary, vessels tracking data from the U.S Coast Guard's Automatic Identification System was used.

They compared the noise levels from commercial ships today with historically lower noise conditions nearly a half-century ago. During the study they noticed that the right whales have lost, on average, 63 to 67 percent of their communication space in the sanctuary and surrounding waters.

"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," said Leila Hatch, Ph.D., 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."

"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," said Christopher Clark, Ph.D., director of Cornell's bioacoustics research program and a co-author of the work. "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."

Through this study the authors show the impact of chronic and wide ranging noise and suggest that this should be incorporated into comprehensive plans that manage the increasing effects of offshore human activities on marine species.

The findings were carried in the August 15 journal Conservation Biology.