Since the 1980s, scientists have observed a link between sea-echography systems and pointed whales that seem to kill themselves – by deliberately stranding on beaches. Now, researchers have perhaps revealed the horrific reason why.
In short, the sound pulses seem to scare the whales to death, act like a shot of adrenaline in a human and cause deadly changes in their otherwise perfectly calibrated diving techniques.
By studying massive stranding events (MSEs) from recent history, the team discovered that spit snout divers have a kind of decompression sickness (also known as & # 39; the curves & & amp;) & divers; & # 39; have when they feel sonar. When they panic, their veins fill with nitrogen gas bubbles, their brains suffer from severe bleeding and other organs become damaged.
"In the presence of sonar, they are stressed and swim powerfully away from the sound source, changing their diving patterns," one of the researchers, Yara Bernaldo de Quiros from the University of Las Palmas de Gran Canaria in Spain, told AFP.
"The stress reaction, in other words, lifts the dive response, causing the animals to accumulate nitrogen."
The end result is that these poor creatures die in mortal fear after getting the whale version of the bends – not something you would normally expect from whales who are so adept at deep water navigation.
Usually these animals naturally lower their heart rate to reduce oxygen consumption and prevent nitrogen build-up when they dive far below the surface. Unfortunately, it seems that a sonar outburst actually suppresses these precautions.
The researchers weighed the evidence from about 121 MSEs between 1960 and 2004, focusing on the autopsies of 10 dead whales stranded in 2002 after a nearby sea exercise in the Canary Islands.
It is here that the effects of decompression sickness were noticed, as they have been at other stranding events that the researchers looked at.
Although the team notes that the effects of sonar on whales appear to "vary between individuals or populations," and "predisposing factors may contribute to individual results," there seems to be a common thread in terms of what happens to these unsuspecting mammals.
This applies in particular to Cuvier's beak fish (Ziphius cavirostris) – of the 121 MSEs that we mentioned, 61 were Cagnier's beaked dolphins and the researchers say they are particularly vulnerable to sonar.
There is also a certain type of sonar that one has to worry about: mid-frequency active sonar (MFAS), in the range of about 5 kilohertz.
Now the researchers want the new report that the use of such sonar technology is prohibited in areas where whales are known to live – such a ban applies since the incidents in 2002 in the Canary Islands.
"Until then, the Canary Islands were a hotspot for this kind of atypical stranding," the Quiros told AFP. "No one has happened since the moratorium."
The research is published in the Royal Society Journal Proceedings B.