Every year, hundreds of marine mammals, mostly whales and dolphins, beach themselves and die. Some environmentalists claim the naval use of sonar causes some of the beaching. They say the loud bursts of sound cause ear and brain lesions and force the animals out of the water. The US Navy rejects most of the accusations. VOA producer Zulima Palacio prepared this report, narrated by Melinda Smith.
Last January, 37 whales of three different species beached themselves on the North Carolina shore; six of them were pregnant when they died. A few weeks later 60 rough-tooth dolphins beached themselves in Florida.
On both occasions, U.S. Navy vessels were nearby, conducting training exercises in the use of deep-water sonar. The beaching is still under investigation.
Michael Jasny, a senior consultant for the Natural Resources Defense Council -- an environmental organization that tries to protect marine mammals -- says, "I think we don't understand the magnitude of the impact that these sound sources have on whales. We know these sound sources can disrupt feeding behavior, they can interfere with the singing of humpback whales, it can cause some species to strand, we know it produces a whole syndrome of internal injury in certain species of animals."
On a few occasions, some scientists say, there has been a clear correlation between the use of mid-frequency sonar and the stranding of marine mammals.
Scientists are concerned, not only about the impact of high intensity sonar use, but also about the dramatic increase of noise in the oceans.
David Cuttingham is the Director of the U.S. Marine Mammal Commission. "There are a number of scientists who think over the long term that the chronic impacts of raising the noise level in the ocean could have a bigger negative impact on the whale populations than the rather isolated acute incidents.
Rear Admiral Steven Tomaszeski, Oceanographer of the Navy, says, "We know more about the Right whale than any mammal in the world's oceans. We do not know where the right whale goes for 6 months of the year. We have no idea. And that's the whale we know most about."
While he supports the idea of protecting marine mammals, he insists that the mid-frequency sonar on Navy ships and submarines provides a targeting capability that keeps the U.S. free and strong.
"We're not going to compromise national security because people think that we are harming whales. It is just not going to happen. But we want to study the whales, the mammals, specifically in the effects of sonar."
While the records of marine mammals inexplicably stranding go back to the 1800s, the scientific community and environmentalists around the world have voiced their deep concern over the increased use of sonar.
The European Parliament has called on its members to stop deploying high intensity active sonar until more is known about the harm it can cause to marine mammals.