Since the 1980s, scientists have seen the connection between naval sonar systems and beak whales, seemingly killing – by deliberately reaching the beach. Now scientists may have uncovered a terrible reason why.
In short, sound impulses seem to scare the whales to death, act like a man in the form of adrenaline and cause fatal changes in otherwise perfectly calibrated diving techniques.
Exploring recent events that occurred in massive events (MSEs), it has been found that beak whales are wearing a decompression sickness (also known as "bends" or "diving disease") when they feel the sonar. When the panic is filled with bubbles of nitrogen, their brains suffer from severe bleeding and other organs are damaged.
"In the presence of the sonar they are highlighted and swim strongly from the source of the sound, changing their sample of diving," said one of the scientists Yara Bernaldo de Quiros of the University of Las Palmas de Gran Canaria in Spain.
"Stress reaction, in other words, prevents a response to diving that accumulates nitrogen on animals."
The ultimate result is that these bad creatures will die in agony after they've got a whale version of the bends – not something you would normally expect from whales that are so wandering when navigating deep underwater.
Typically, these animals naturally reduce heart rate to reduce oxygen consumption and prevent the accumulation of nitrogen when it is immersed beneath the surface. Tragically, sonar blasting appears to precede these measures.
Scientists considered evidence from about 121 MSEs from 1960 to 2004, focusing in particular on the autopsy of the ten dead whales trapped in the Canary Islands in 2002 following a nearby naval exercise.
There have been decompression sicknesses here, because they occurred in other events that the researchers were looking at.
While the team notes that the effects of sonar on whales seem to "vary among individuals or populations" and "predisposing factors can contribute to individual results," it seems to be a common thread of what happens to these unsuspecting mammals.
This is especially true for the Cuvier beak whale (Ziphius cavirostris) – Of the 121 MSEs we mentioned, 61 included Cuvier's beaks, and scientists believe it appears to be particularly vulnerable to sonar.
There is also a special kind of sonar that has to worry about: Medium Frequency Active Sonar (MFAS), in the range of about 5 kilohertz.
Now, scientists are asking for the use of such sonar technologies to be prohibited in areas where whales are known – such a ban was introduced in the Canary Islands since 2002.
"Until then, the Canary Islands have been hotspots for this kind of atypical repayment," said de Quiros AFP. "There has been no moratorium since the moratorium."
The research was published in The Royal Society Journal Proceedings B.