This is a MYTH
The fact is that observations as far back as Aristotle and illustrations from the Middle Ages show us that marine mammals have been stranding long before people created underwater sounds. There are many causes of strandings, such as diseases, ship-strikes, injuries, storms, and entanglement. One controversial and unresolved issue, however, is how the use of military sonar relates to strandings, particularly strandings of some species of beaked whales. In several cases worldwide, there is sufficient information about the timing and location of both military sonar operations and beaked whale strandings to connect the strandings with sonar use. In the last fifty years, fewer than 50 cetaceans are known to have stranded in vicinity to sonar operations. In comparison, about 1,000 cetaceans and 2,500 pinnipeds strand annually in the U.S. alone, with no relationship to anthropogenic sound.
How do we know?
Determining the exact cause of a stranding or death of a stranded animal is often difficult, and most often, scientists have little or no information about the animal’s history or the circumstances that preceded the stranding. On average, a cause of death can be determined in only about half of all stranding cases. Scientists do their best to determine cause and effect, but, in the case of marine mammal strandings, they often rely on correlated events to inform their conclusions. For example, mass strandings of beaked whales are rare, with only 136 mass stranding events reported from 1874 to 2004. Two of these events were associated with the use, timing, and location of sonar.
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