Blog Tags: SONAR
In the last three months, more than 3,000 dolphins have washed ashore in Peru, most likely due to offshore oil exploration. Oil companies in the region often use sonar or acoustic soundings to detect oil beneath the floor of the sea, and dolphins and whales can be affected because of their sensitivity to sound.
Toothed whales, including dolphins and porpoises, have evolved to be able to echolocate. Instead of having two nostrils like other mammals and baleen whales, toothed whales have only one which is used as their blowhole. A whale emits squeaks and whistles from its blowhole, and the sounds bounce off objects in the water, providing an echo. The other nostril has developed into a fatty tissue known as the melon, which is used to receive and focus the returning echoes.
Hearing is considered to be whales’ most important sense, used not only for navigating but also for feeding, bonding with offspring, and finding mates. Noise pollution cause changes in calling behavior, but can also cause whales to change their diving habits which can result in “the bends,” when nitrogen bubbles get trapped in the body.
Sonar can be extremely loud (imagine the sound of 2,000 jet planes), with sound waves travelling hundreds of miles through the ocean. Noise levels this high can cause fatal injuries, similar to those seen in many strandings around the world. As the world’s oceans become noisier, they also become more dangerous for whales and dolphins.
A recent study conducted at the University of Hawaii provides “sound” evidence that sonar induces temporary deafness in bottlenose dolphins. Many have long blamed man-made noise -- mainly sonar used by the navy -- for mass strandings of whale and dolphin species. Although this study does not provide concrete proof that submarine and warship sonar activity is causing strandings, it does prove definitively that sonar activity can affect cetaceans if they are close enough to the source and exposed over a prolonged period of time. Whales and dolphins use sound for navigation and temporary deafness can leave them disoriented. They are traveling over very large distances and cannot afford to lose their sense of direction. If they were to accidentally swim into a shallow area or be washed ashore, they could rapidly become dehydrated and die.
Next spring, the Supreme Court will weigh in on the U.S. Navy’s use of high-intensity, mid-frequency sonar off the southern California coast. Use of this type of sonar, which the Navy admits may significantly disturb or injure an estimated 170,000 marine mammals, was challenged in court based on protections found in the National Environmental Policy Act of 1970. Now that oral arguments before the Supreme Court have concluded, we must wait for its decision in 2009. But when you’re as passionate about the issues as our staff and supporters, waiting can be incredibly difficult, so thanks to a Wavemaker in St. Augustine, FL named Marcella, I have something that you can do to help protect marine mammals and other ocean wildlife from sonar.
In further noisy ocean news this past week, our nation's highest court heard oral arguments in the dispute over the Navy's use of mid-frequency active sonar off the coast. The sonar has been associated with whale injury and beach strandings; meanwhile, the Navy argues that halting or restricting sonar training exercises in any way harms national security. According to the Natural Resources Defense Council (NRDC), the plaintiff in the case, many whales that have been beached as a result of sonar have suffered physical trauma, including bleeding around the brain, ears and other tissues. In addition, many have shown symptoms akin to a severe case of "the bends" -- the illness that can kill scuba divers who surface quickly from deep water, implying that the whales' dive patterns are altered. Sonar has also been shown to disrupt feeding and other vital behavior and to cause a wide range of species to panic and flee. The NRDC case is specific to training exercises in the Pacific Ocean and whether the Navy has to be environmentally responsible in its routine trainings by reducing their impacts to whales.
Those Europeans always seem to be - environmentally, at least - one step ahead. They have seafood labels, wind farms, viable Green parties...and now a multi-national body acknowledging the danger of navy sonar testing to whales and dolphins. Last week, by a vote of 441 to 15 (with 14 abstentions), the European Parliament adopted a resolution asking its member states to quit sonar testing until scientists have fully assessed its effect on ocean life.
From Reuters -- "Dead Whales Land in Canaries After Naval Exercises":
Two dead whales have landed in Spain's Canary Islands, raising fears they may have been hurt by NATO military exercises off Morocco and that more could have died, officials said on Friday.
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