Whales Benefit From Action on Ocean Noise
- by Pallab Ghosh
Scientists are working to reduce the noise levels experienced by whales from North Atlantic shipping.
The blare is making it difficult for the animals to communicate with each other, which in turn is affecting their ability to find food and mates.
The researchers have persuaded shipping companies to change their routes in and around the Boston area.
Sea captains use an iPad App that helps them to understand the locations of the whales and when to slow down.
The change in operations has helped to lower the din. Scientists hope it will also limit the number accidental collisions.
The waters off New England are a home to many species of whale. Many are now suffering because of increased noise levels.
Research presented at the annual meeting of the American Association for the Advancement of Science (AAAS) suggests that it has doubled each decade over the past 30 years.
Dr Mark Baumgartner of the Woods Hole Oceanographic Institution played me the sound of a passing container ship as a whale might hear it.
It was a thunderous, unchanging drone.
"How would you like to have that in your bedroom, your kitchen, your work all the time?" he asked plaintively. "That’s what the acoustic environment for whales is like all the time."
The effect is to reduce the range whales can communicate.
Social communication is necessary so that they can get together for important activities, such as mating, and it is unclear just what the ramifications of cutting off that communication will mean for them.
But the ships are not just disrupting communication; they also collide with whales from time to time.
Dr Dave Wiley who works for the National Oceanic and Atmospheric Administration has seen the consequences at first hand.
"Our scientists found shattered bone and large hematomas which are indicative of a ship strike," he told BBC News.
Each year, there are one or two North Atlantic Right Whales stuck by ships in the area. Although that does not sound like a lot, it was enough to concern environmental groups because it is thought that there are just 500 of these animals left in the wild and mothers with calves get hit more frequently.
To kill a whale
During the 1980s, a technique was being developed by the US navy to detect submarines - a sonar, which unlike regular sonars (which rely on sound created by other vessels) worked through emitting a high power, low frequency sound and then listening for returning echoes. The noise emitted was around 230 decibels, which is around 10,000 times louder than a passenger aeroplane taking off.
As you might imagine, this had some severe effects on marine life:
It was shown that some animals further away from the source were deaf (which is a drawback for animals which rely on being able to hear for reproduction and even feeding sometimes). Closer to the source, 13 Cuvier’s Beaked Whales were found washed up on shore with severe gas embolisms and haemorraging as a result of the pressure waves created by the sound.
180 decibels causes permanent death of hearing tissues in humans, why should the marine environment (which is even more sensitive to loud noises, due to the nature of water) be exposed to it? surely any technique which made use of such loud noises would be banned on land.
Above: How active sonar works, gas embolism in a dolphin liver and a Cuvier’s Beaked Whale.
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 Maine’s 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 study’s Ocean Acoustic Waveguide Remote Sensing equipment was not being used. This suggests the whales reacted to the low-level sounds by silencing their songs.
“It’s 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.