Suicidal behaviour in beaked whales is driven by exposure to naval sonar, scientists have discovered.
The mass beaked whale deaths have been causing alarm among marine biologists since the dead bodies of these beautiful marine animals started washing up on shores since the 1950s.
At the same time, human activity in the oceans developed to include sonar used to detect submarines by the US and NATO allies, which buzzes at around five kilohertz.
A coincidence? Apparently not, unsurprisingly.
Academics have looked into the unusual ‘mass suicide’ behaviour and previously inexplicable deaths of otherwise healthy beached whales and found it corresponds to the navel sonar activity.
The researchers, of the University of Las Palmas de Gran Canaria in Spain, have also found a scientific explanation for the animals’ reaction to the human interruption of their natural habitat.
The findings are very distressing. Essentially, the mammals are driven to suicide by the bends, a reaction in the body also known as decompression sickness.
Lead author Yara Bernaldo de Quiros explained:
In the presence of sonar they are stressed and swim vigorously away from the sound source, changing their diving pattern.
The fear evoked in the beaked whales by the sonar causes gas – nitrogen bubbles to be specific – to form in their bodies in a reaction not dissimilar to when scuba divers suffer from decompression sickness.
Except when humans get the bends, it’s a known potential side effect on rising and falling below surface level – not the knock-on effect of sonar waves hurtling through your home.
Dr Bernaldo de Quiros, in Proceedings of the Royal Society, added:
The stress response, in other words, overrides the diving response, which makes the animals accumulate nitrogen. It’s like an adrenaline shot.
According to the researchers at the University of Las Palmas de Gran Canaria, there were 121 examples of a mass stranding between 1960 and 2004, at least 40 of which were closely linked to naval activities, reports Sky News.
The so-called ‘atypical’ mass strandings didn’t necessarily befall old or sick animals. The only connection found between the animals who suffered deaths of this nature was the date and locations within which they washed ashore.
During one NATO naval exercise in 2002, Dr Bernaldo de Quiros said, 14 whales were stranded over a 36-hour period in the Canary Islands, adding the animals started ‘showing up’ dead on the beaches ‘within a few hours of the sonar being deployed’.
In this case, none of the whales showed any outward signs of disease. But, their veins were filled with nitrogen gas bubbles and their had suffered severe haemorrhaging in their brains.
This undue animal suffering, first uncovered in a 2003 study, led the Spanish government to prohibit naval exercises near the Canary Islands the following year in 2004.
Now, this team of researchers is hoping the new findings – which detail how the beaked whales get caught in a cross-fire we humans may not have expected as a consequence of underwater wars – will force governments to expand protected areas.
They are particularly hoping to protect other areas of ocean where beaked whales are known to congregate.
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