Mystery of ‘suicidal’ whales that beach themselves is SOLVED: Experts discover sonar from ships gives the animals the bends and forces them to strand themselves

  • It has been previously reported that beaked whales have ‘suicidal’ behaviour 
  • A study found that whales are scared of the sonar from ships and submarines 
  • They swim away from the source of the noise 
  • and swim away from it
  • There were 121 beach strandings between 1960 and 2004
  • Autopsies reveal that they suffer from decompression sickness 

The mystery behind why beaked whales are ‘suicidal’ may have finally been solved. 

Sonar commonly used by America and NATO has been revealed to cause decompression sickness, also known as the bends. 

This condition is also known to affect scuba divers and it is believed the condition forces the whales to beach themselves. 

Scientists had previously made the link between beached whales and exposure to naval sonar but research has now found the reason why.  

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21 experts in the Royal Society journal Proceedings B released their findings. Scientists have long known that some beaked whales beach themselves and die in agony after exposure to naval sonar, and now they know why: the giant sea mammals suffer decompression sickness, just like scuba divers.

The fear and stress from the animals when they hear sonar overrides their natural  diving instinct and creates a build up of nitrogen in the blood, leading to the bends. 

In humans this occurs when a diver ascends to the surface too quickly but in whales, it is initiated by fear. 

Whales that suffer from this can often die and wash up on a beach several days later, research finds. 

Mid-frequency active sonar (MFAS) has been used since the 1960s to detect submarines. They emit underwater signals in a range of about 5 kilohertz (kHz). 

This is causing whales, in particular beaked whales, to become scared and swim away from the sound, throwing off their dive pattern.

The fear and stress response, overrides the diving response, which creates a build up of nitrogen in the blood – which is what happens to scuba divers when they get decompression sickness. 

This causes beaked whales, specifically the Cuvier species, to beach. Previously, these were reported as ‘suicidal’ whales. 

Researchers attempting to rescue a stranded beaked whale off the island of Fuerteventura in the Canary Islands in 2002

Through millions of year of evolution, whales have transformed into diving experts capable of plunging miles below the surface foraging for food.

Whales are often able to submerge themselves for hours at a time before needing to return to the surface. 

They have trained themselves to slow down their heart rate and restrict blood flow, which conserves oxygen.  

But in the presence of sonar beaked whales get scared and causes them to react drastically. 

‘In the presence of sonar they are stressed and swim vigorously away from the sound source, changing their diving pattern,’ said lead research Yara Bernaldo de Quiros, a researcher at the Institute of Animal Health at the University of Las Palmas de Gran Canaria, Spain 

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There were 121 mass strandings between 1960 and 2004, with at least 40 linked in time and place with naval activities. 

Autopsies over several years have revealed that these whales experience decompression illness because of sonar, which is commonly associated with scuba divers. 

A build up of nitrogen in the blood encourages erratic behaviour in the animals and  can be fatal.

Often several beaked whales would wash ashore within a day or two, no more than a dozen kilometres apart.

Whales stranded on a beach in Croajingolong National Park, Victoria, Australia in 2018. 25 whales died when they beached on the coast of Australia. 

The deadliest episode was in 2002, when 14 of the animals stranded over a single 36-hour period in the Canary Islands while a NATO naval exercise was occurring. 

‘Within a few hours of the sonar being deployed, the animals started showing up on the beach,’ said Dr de Quiros.

The whales showed no signs of disease or damage on the outside: they had normal body weight and no skin lesions or infections. 

However, autopsies revealed they had nitrogen gas bubbles in the veins and their brains were ravaged by haemorrhaging. 

There was also damage to other organs, as well as damage to the spinal cord and central nervous systems.  

Beaked whales get decompression sickness, similar to what scuba divers get. (Pictured) An Aussie couple free-diving woman mirroring a humpback whales swimming technique. 

A 2003 study in Nature on the possible link between sonar and whale deaths led to Spain banning such naval exercises around the Canary Islands in 2004.

‘Up until then, the Canaries were a hotspot for kind strandings,’ said Dr de Quiros. ‘Since the moratorium, none have occurred.’ 

Similar bans have been called for in other regions where at-risk whales are known to congregate.

The Cuvier’s grows up to seven metres (23 feet) and eats mainly deep-water squid and fish. Its upwardly turned mouth gives the impression of a permanent smile.

The whale is listed as ‘vulnerable’ on the IUCN Red List of endangered species, and is thought to have a global population of 5,000 to 7,000.

Other threats include ship strikes, ocean pollution and shifting habitats caused by climate change. 


Decompression illness (DCI) affects scuba divers, aviators, astronauts and compressed-air workers. 

It occurs in approximately 1,000 U.S. scuba divers each year and tend to hit randomly.

DCI sickness occurs when nitrogen bubbles form in blood vessels, blocking it. 

Also know as air or gas embolism, DCI can cause serious and potentially fatal conditions, such as a stroke or heart attack. 

The main risk is a reduction in ambient pressure, but there is also a chance in DCI occurring through deep/long dives, cold water, hard exercise at depth and rapid ascents.


  • Joint or muscle pain
  • Low blood pressure
  • Dizziness
  • Irregular heartbeat
  • Chest Pain
  • Skin rash   
  • Fast breathing 


  • Relax and breath normally when surfacing.  
  • Limit the duration and length of dives
  • Avoid exercise before, during and after a dive
  • Stay hydrated 


After a diver with an air or gas embolism has received emergency medical attention and their condition has stabilised, they’ll be transferred to a hyperbaric chamber, where they will lie in for several hours. 

The high pressure restores normal blood flow and oxygen to the body’s tissues, And reduces the size of the air bubbles in the body. 


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