Pulsing sounds made by technology used to monitor fish stocks may affect how baleen whales communicate, even at great distances.
Marine biologists working in Massachusetts waters noticed that humpback whales sang less during the fall of 2006, when a low frequency signal showed up in their recordings. They eventually traced the signal to some acoustic sensing equipment that was part of a scientific study off Maines coast, about 120 miles from where they were studying seasonal changes in whale songs in Georges Bank.
The scientists recorded more frequent whale vocalizations (listen below) during the same time of year in 2008 and 2009, when the studys Ocean Acoustic Waveguide Remote Sensing equipment was not being used. This suggests the whales reacted to the low-level sounds by silencing their songs.
Its fascinating that we saw this behavioral response over such a large distance, said Denise Risch, a marine biologist at the National Oceanic and Atmospheric Association and lead author of research published Jan. 11 in PLoS One.
Previous research suggests that nearby underwater noise from ships, airguns, underwater explosions and sonar may cause hearing damage and changes in feeding, mating and communication among marine mammals. But this is the first time whales have been reported reacting to man-made sounds from so far away.
Whales are extremely social creatures with a remarkable ability to play with sounds. When a male humpback starts to sing, it may keep going for weeks at a time, says Christopher Clark, the director of the Bioacoustics Research Program at Cornell University. Clark, who was not involved in the study but has collaborated with the researchers, studies various species of whales in Mexico and Hawaii.
In mating grounds, males sing to attract the ladies and show off to other males, but scientists dont yet know why they sing in feeding grounds like the ones in Georges Bank.
Source and full article: http://www.wired.com/wiredscience/2012/01/underwater-noise-disturbs-whales-120-miles-away/
Research Report on PLoS One: