Military exercises blamed for whales stranded on beach

Military exercises involving blasts of underwater sound could be the reason why whales and dolphins become stranded on beaches, a study has found.

Military exercises involving blasts of underwater sound could be the reason why whales and dolphins become stranded on beaches, a study has found.

The blasts from active sonar, used to detect submarines, may cause dolphins and whales to suffer a form of decompression sicknesssimilar to "the bends" suffered by deep-sea divers.

Scientists believe they have found evidence to explain why many strandings of whales and dolphins appear to coincide with naval exercises involving active sonar.

Marine mammologists discovered signs of decompression sickness during post-mortem examinations of whales which beached themselves in the Canary Islands four hours after the start of a Spanish naval exercise in September 2002, where active sonar was used.

Antonio Fernandez, professor of pathology at the University of Las Palma de Gran Canaria, who examined 14 beaked whales found beached in the area where the exercise took place, said the link was circumstantial but strong.

"The detailed examination of the mass-stranded beaked whales in the Canaries in 2002 suggests that naval sonar could induce a condition similar to decompression sickness," Professor Fernandez said. "More research is needed to confirm this mechanism and to determine what level of sound can induce this process in exposed whales and dolphins."

The study, in the journal Nature, also involved government-funded British scientists who have performed more than 2,500 post-mortem examinations on sea mammals stranded off Britain over the past decade.

Paul Jepson, of the Institute of Zoology in London and a member of the Anglo-Spanish team, said: "The link between military sonar and stranded sea mammals has been established. Our study suggests a potential mechanism."

Decompression sickness happens when dissolved gases in the tissues of a diving mammal come out of solution because the animal rises to the surface too quickly. The dissolved gases, mostly nitrogen, form bubbles which can press against nerves and joints to cause severe pain and tissue damage. Dr Jepson said examination of stranded sea mammals in Britain showed that they can experience the effects of decompression sickness, challenging the notion that cetaceans (whales and dolphins) cannot suffer from the bends.

In some beached sea mammals, gas cavities had formed to such an extent in their livers that the texture of the dissected organs looked like aerated chocolate, Dr Jepson added. "A small number of stranded animals had gas bubbles and associated tissue injuries.

"Although decompression sickness was previously unheard of in marine mammals, we concluded that a form of marine mammal decompression sickness was the most likely cause."

The scientists have ruled out bacterial infections or other post-mortem changes to the corpses as the possible causes of the tissue bubbles. But an unresolved question is: how does active sonar causes decompression sickness? The most obvious answer is that the sudden loud noises, greater than any natural underwater sound, may startle whales and dolphins, causing them to surface too quickly.

Beaked whales, such as bottlenose and sperm whales, dive to great depths and normally take many minutes to surface, slowly allowing dissolved gases in their bloodstream to be released into the lungs. Anything that interferes with this carefully evolved behaviour may increase the risk of decompression sickness, leading to disorientation and stranding.

Another possibility, proposed by Dorian Houser, of the US Navy marine mammal programme in San Diego, is that sound waves from active sonar interfere with the way diving sea mammals safely store dissolved gases.

Dr Houser has proposed a mathematical model of how sonic blasts have a direct impact on dissolved gases by vibrating microscopic bubbles in the bloodstream, causing them to expand to a size that can cause tissue damage.

The work, which was largely theoretical, found the diving behaviour of beaked whales, which gulp a large amount of air before a dive, makes them more vulnerable to this effect because levels of super-saturated nitrogen in their bloodstream can more than triple by the end of a dive.

Other sea mammals, such as seals, breathe out before a dive, which allows their lungs to collapse at a shallower depth. This helps prevent nitrogen building in the bloodstream while they are underwater.

Start your day with The Independent, sign up for daily news emails
Life and Style
Steve Shaw shows Kate how to get wet behind the ears and how to align her neck
healthSteven Shaw - the 'Buddha of Breaststroke' - applies Alexander Technique to the watery sport
A poster by Durham Constabulary
Cameron Jerome
footballCanaries beat Boro to gain promotion to the Premier League
Arts and Entertainment
Performers drink tea at the Glastonbury festival in 2010
Arts and Entertainment
Emily McDowell Card that reads:
artCancer survivor Emily McDowell kicks back at the clichés
footballShirt then goes on sale on Gumtree
Arts and Entertainment
Twin Peaks stars Joan Chen, Michael Ontkean, Kyle Maclachlan and Piper Laurie
tvBadalamenti on board for third series
Life and Style
Standing room only: the terraces at Villa Park in 1935
Ben Stokes celebrates with his team mates after bowling Brendon McCullum
sportEngland vs New Zealand report
Amal Clooney has joined the legal team defending 'The Hooden Men'
ebookA unique anthology of reporting and analysis of a crucial period of history
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Guru Careers: Software Developer / C# Developer

£40-50K: Guru Careers: We are seeking an experienced Software / C# Developer w...

Guru Careers: Software Developer

£35 - 40k + Benefits: Guru Careers: We are seeking a Software Developer (JavaS...

SThree: Trainee Recruitment Consultant / Resourcer

£18000 - £23000 per annum + Commission: SThree: As a Trainee Recruitment Consu...

Ashdown Group: UI Developer - (UI, HTML, CSS, JavaScript, AngularJS)

£25000 - £40000 per annum: Ashdown Group: UI Developer - (UI, JavaScript, HTML...

Day In a Page

Abuse - and the hell that came afterwards

Abuse - and the hell that follows

James Rhodes on the extraordinary legal battle to publish his memoir
Why we need a 'tranquility map' of England, according to campaigners

It's oh so quiet!

The case for a 'tranquility map' of England
'Timeless fashion': It may be a paradox, but the industry loves it

'Timeless fashion'

It may be a paradox, but the industry loves it
If the West needs a bridge to the 'moderates' inside Isis, maybe we could have done with Osama bin Laden staying alive after all

Could have done with Osama bin Laden staying alive?

Robert Fisk on the Fountainheads of World Evil in 2011 - and 2015
New exhibition celebrates the evolution of swimwear

Evolution of swimwear

From bathing dresses in the twenties to modern bikinis
Sun, sex and an anthropological study: One British academic's summer of hell in Magaluf

Sun, sex and an anthropological study

One academic’s summer of hell in Magaluf
From Shakespeare to Rising Damp... to Vicious

Frances de la Tour's 50-year triumph

'Rising Damp' brought De la Tour such recognition that she could be forgiven if she'd never been able to move on. But at 70, she continues to flourish - and to beguile
'That Whitsun, I was late getting away...'

Ian McMillan on the Whitsun Weddings

This weekend is Whitsun, and while the festival may no longer resonate, Larkin's best-loved poem, lives on - along with the train journey at the heart of it
Kathryn Williams explores the works and influences of Sylvia Plath in a new light

Songs from the bell jar

Kathryn Williams explores the works and influences of Sylvia Plath
How one man's day in high heels showed him that Cannes must change its 'no flats' policy

One man's day in high heels

...showed him that Cannes must change its 'flats' policy
Is a quiet crusade to reform executive pay bearing fruit?

Is a quiet crusade to reform executive pay bearing fruit?

Dominic Rossi of Fidelity says his pressure on business to control rewards is working. But why aren’t other fund managers helping?
The King David Hotel gives precious work to Palestinians - unless peace talks are on

King David Hotel: Palestinians not included

The King David is special to Jerusalem. Nick Kochan checked in and discovered it has some special arrangements, too
More people moving from Australia to New Zealand than in the other direction for first time in 24 years

End of the Aussie brain drain

More people moving from Australia to New Zealand than in the other direction for first time in 24 years
Meditation is touted as a cure for mental instability but can it actually be bad for you?

Can meditation be bad for you?

Researching a mass murder, Dr Miguel Farias discovered that, far from bringing inner peace, meditation can leave devotees in pieces
Eurovision 2015: Australians will be cheering on their first-ever entrant this Saturday

Australia's first-ever Eurovision entrant

Australia, a nation of kitsch-worshippers, has always loved the Eurovision Song Contest. Maggie Alderson says it'll fit in fine