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Scientists listen to whale hearing via 'third ear'

Reuters UK

25th June 2004

By Meraiah Foley

Scientists have long studied haunting whale songs, but now they are investigating what the whales make of ocean noises to determine whether freighters, military sonars and oil drilling are harming the giant mammals.

"We actually know very little about the way whales perceive sound and use sound," said Michael Noad, the scientist at the University of Queensland who heads the U.S.-navy funded study.

Scientists and green groups have voiced concern over the impact on whales and other sea mammals of sounds generated by shipping, the military and oil rigs, Noad said Friday.

U.S. officials linked a mass stranding and the death of several whale species in the Bahamas in March 2000 to the use of a navy mid-frequency sonar system.

The Australian study is being funded by the U.S. Office of Naval Research and is focusing on the meaning of whale songs and how whales react to other noises.

The study is taking place off Peregian Beach of Australia's tropical eastern state Queensland, in a "commercial shipping highway" used by migrating humpback whales.

Marine scientists have long believed that humpback whale songs depend on the animals' migratory paths, with populations inhabiting different oceans singing quite distinct songs.

Whale songs run seven to 15 minutes and contain themes, like verses in human songs. Scientists say some are "love songs," sung by male whales to attract females during the mating season.

Noad said until scientists learn more about the hearing system and sound perception of whales, they would not be able to understand how man-made marine noises impact on whales.

"There is plenty of behavioural evidence that whales do avoid, to greater or lesser extent, loud industrial sounds in the ocean," Noad said.

"If you did stick a very loud sound source in the middle of a breeding ground of sensitive whales, it almost certainly would have a deleterious effect on those animals," he said.

The whale study involves placing suction cups on whales to try and measure what they hear. "The suction tags have a hydrophone which acts like another ear stuck on the side of the whales, allowing us to hear what they hear, as well as sensing their movements and what depth they go to," said Noad.

The study will also measure ambient ocean noise, particularly surf noise, as scientists believe whales may use sound to help them navigate during migration and will playback whale songs to measure whale reactions.