Underwater trap

Whale deaths may be caused by military sonars

One of the most common versions of the mass suicide of whales and dolphins washing ashore has received new confirmation. Through a series of experiments involving dolphins, researchers from the Hawaiian Institute of Marine Biology demonstrated the effects of military sonar on aquatic mammals. During the experiment, it turned out that a dolphin exposed to the radar can “lose hearing” for almost 40 minutes. and, therefore, lose orientation in space, Newsru.com reports. The increased interest in this topic is easy to explain - in February and March alone, several mass whale strandings were recorded in the southeastern Pacific Ocean. There are hundreds of animals that have died this year on the coasts of Australia, Tasmania and small islands.

Actually, the very fact that the impact of warship echolocators on marine mammals is mostly negative does not need proof for a long time. Conservationists have long collected a lot of evidence, which they successfully use not only in scientific discussions, but also in legal battles. In 2006, the verdict of a federal court in California, which prohibited the US Navy from using sonars during exercises near traditional whale migration sites, caused a great stir. The court found convincing the documents provided by American ecologists that low-frequency sonars can not only interfere with the echolocation of mammals, but also directly contribute to their death. British animal rights activists, who investigated the circumstances of the mass death of whales off the Hebrides Islands near Scotland, suggested that the cause of death could be not only disorientation - mammals that found themselves in the zone where military echolocators were operating had to quickly “change the horizon” under the influence of powerful sound waves, surfacing from depth to surface. This caused attacks of decompression sickness.

But opponents of this version, and primarily the military, had serious counterarguments. The main one is very simple: the proximity at sea of ​​warships and whales rarely ends in the suicide of the latter. Scientists from the Hawaiian Institute of Marine Biology, in their work, which was recently reported in the journal Biology Letters, tried to find an explanation for this. In experiments involving bottlenose dolphins, they found that the high speed of marine animals most often allows them to quickly leave the sonar area. The “stun” effect, which disorients the dolphin, occurs only after two minutes of being near the echolocator. Dr. Aran Mooney, who participated in the study, as quoted by the British The Times, claims that this time is enough for the dolphin to move to a safe distance - if it does not fall into an “underwater sound trap.”

With this term, Dr. Mooney refers to the situation when the sound waves of the echolocator are “distorted” in layers of sea water, bypassing warm ones and reflecting from cold ones. A similar effect is produced by the uneven topography of the seabed. According to scientists, it is the combination of these factors - the complex topography of the bottom and the “layering” of the water - that is observed near the Hawaiian and Bahamas islands, where several cases of mass death of whales coincided with the activation of the military and the use of sonars. Since sound is as important for cetaceans as vision for humans, falling into a sound trap meant for them a complete loss of orientation in space. The animals unexpectedly found themselves on the shore, and not all were saved.

At the same time, researchers from the Hawaiian Institute of Marine Biology warn that they do not claim to have a complete and comprehensive explanation for the phenomenon of mass suicides of whales and dolphins, which may be caused by other reasons not related to the use of powerful echolocators by the military.

Anastasia KRAVETS