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 and are on the brink of extinction. Recent estimates put the population of North Atlantic right whales at approximately 350 to 550 animals.
According to a NOAA-led paper published in the journal Conservation Biology, high levels of background noise, mainly due to ships, have reduced the ability of critically endangered North Atlantic right whales to communicate with each other by about two-thirds.
An example of predicted received levels (71-224 Hz, dB re 1µPa, scale far right) produced by calling right whales, large commercial ships and wind-dependent background noise within the study area (boundaries of the sanctuary outlined in black) calculated every 10 minutes over a nine hour period. Download here (Photo courtesy NOAA and Cornell Lab of Ornithology).
From 2007 until 2010, a team of scientists used acoustic recorders to monitor noise levels, measure levels of sound associated with vessels, and to record distinctive sounds made by multiple species of endangered baleen whales, including “up-calls” made by right whales to maintain contact with each other. More than 22,000 right whale contact calls were documented as part of the study during April 2008.
Vessel-tracking data from the U.S. Coast Guard’s Automatic Identification System was used to calculate noise from vessels inside and outside of the Stellwagen Bank National Marine Sanctuary. By further comparing noise levels from commercial ships today with historically lower noise conditions nearly a half-century ago, the authors estimate that right whales have lost, on average, 63 to 67 percent of their communication space in the sanctuary and surrounding waters.
The authors suggest that the impacts of chronic and wide-ranging noise should be incorporated into comprehensive plans that seek to manage the cumulative effects of offshore human activities on marine species and their habitats.
A team of scientists from the Stellwagen Bank National Marine Sanctuary, Cornell Lab of Ornithology, NOAA Fisheries Northeast Fisheries Science Center, and Marine Acoustics Inc. were involved in the study. This study was funded under the National Oceanographic Partnership Program. The research was published in Conservation Biology.