Noise pollution causing 'cocktail party effect' for whales and dolphins

Human-made noises are drowning out the sounds whales and dolphins use to communicate and find mates, environmental groups said Wednesday.

Noise pollution, partially caused by commercial shipping, seismic surveys and improved sonar technology, is making it harder for the animals, which use sounds to communicate over thousands of kilometres, to forage and mate.

As a result, the animals are losing touch with each other, environmental experts said at a UN wildlife conference held in Rome.

"Call it a cocktail party effect," said Mark Simmonds, of the Whale and Dolphin Conservation Society. "You have to speak louder and louder until no one can hear each other anymore."

Environmental groups believe increased levels of noise pollution are behind a growing number of beached whales and dolphins, he added. Many of the beached whales and dolphins in question exhibit symptoms of decompression sickness, known as the bends, a condition afflicting divers who surface too quickly.

Some environmentalists believe the sound waves caused by sonar and seismic surveys are causing the animals to dive and surface beyond their physical limits, Simmonds said.

One of the aims of the conference is coming up with ways to reduce noise pollution in the worlds oceans, such as rerouting ships and banning sonar use in areas known to be inhabited by endangered whales and dolphins.