Marine Biology

Mixed Signals

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"Mixed Signals"
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Whales are acoustic mammals. They use their hearing to follow migratory routes, find food, care for their young and locate one another. The process is called echolocation. Whale songs have long been studied to try and determine just how valuable the method of communication is. It's been said over and over "A deaf whale is a dead whale."

It would make sense the use of sonar would have some effect on the whales. The exact effect is a bit of a controversy. Some things have been proven. For example, research has proven that humpback whales stop singing when they are exposed to LFA (low frequency active) sonar. This type of sonar is long range and doesn't use a constant tone, but instead uses a transmission of various waveforms that vary in duration and frequency. It is designed to seek out quieter and more sophisticated submarines. They can be as far away from the projectors emitting the sound and still stop singing. So it does do something.

In March of 2000, 13 beaked whales stranded themselves on the beach after being exposed to sonar. Seven of them died. An investigation later found that the whales had hemorrhaging around the ears and the eyes. This was a clear indication of severe acoustic trauma. The governments study further concluded that the stranding and subsequent deaths had been cause by mid-frequency active sonar used by the Navy ship. This is a more mild form of sonar compared to LFA sonar. Since this incident the area's population of beaked whales has disappeared. It is unclear if they abandoned their habitat and moved on or died at sea.

Dr. Darlene Ketten had this to say about the incident. "The animals were driven to strand by the stress of being exposed to this particular sonar." She sited the post mortem examination had severely damaged the inner ears.

Joe Reynolds is a long time whale campaigner and lobbyist. He had this to say on his concern of future problems. "Very intense sound can have severe consequences, even death," he says. "It causes us great concern that the navy proposed to deploy one the loudest sound systems devised by man over 80 per cent of the world's oceans without really understanding what the implications are. Whales are already under threat from pollution, fishing nets and collisions with boats. Although the research is inconclusive, conservationists say we should avoid any further risks to them."

Common sense tells us that sonar has some effect on the whales. It is disruptive to their every day life. Can we live without it or at the very least limit it? If we can it seems that we should.


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