Beached whales may have been confused by military sonar, experts suspect

Three whales have washed up on beaches along west coast in last two weeks

A sperm whale measuring around 12m Long washed up on Streedagh beach in Co Sligo on Wednesday. Photograph: Colin Gillen/

A sperm whale measuring around 12m Long washed up on Streedagh beach in Co Sligo on Wednesday. Photograph: Colin Gillen/


Several whales washed ashore in Ireland over recent weeks may have been confused while trying to swim away from underwater military sonar signals, experts suspect.

A 12m long female sperm whale found dead on Streedagh beach in Co Sligo in recent days is one of three washed up between Donegal and Galway within the last two weeks.

A fourth was spotted in “poor condition” off the coast of Donegal.

Sean O’Callaghan, science officer with the Irish Whale and Dolphin Group (IWGD), which is carrying out a post mortem examination on the dead mammal in Co Sligo, said it was unlikely natural causes are to blame.

“There is no indication of the whales having been hit by a ship or anything like that – we are not too sure at the moment, it is fairly puzzling,” he said.

Initial investigations show there was no plastic pollution inside the whale either.

“It seems a bit too unusual for it all to be of natural causes - four recorded dead in such a short space of time,” said Mr O’Callaghan.

“Typically we might record one or two sperm whales stranded or dead at sea.

“Four within a week and half of each other is quite a lot, all within a fairly small geographic area. It hasn’t happened before with sperm whales.”

Last August and September, up to 13 beaked whales – an even more elusive species than sperm whales – washed ashore along the coast within weeks of each other.

“Potentially those species were affected by noise pollution, such as military sonar but investigations are ongoing between Ireland and Scotland to understand that,” he told RTÉ Radio.

Mr O’Callaghan said the IWGD is speaking with counterparts in Scotland about trends there recently where large numbers of whales have washed ashore since last year.

Research published last month suggests sonar from naval ships can affect the behaviour of whales from a longer distance than first thought.

Using animal-attached sensors and deep-ocean acoustic listening devices, professors from St Andrews and Iceland universities found whales would swim away, go into a deep dive and also stop feeding upon hearing the military sounds.

Tests conducted on 12 northern bottlenose whales near Jan Mayen, an island north of Iceland, showed the whales swimming away from for several hours when exposed to a certain sound level, some up to 28km away.

The British Royal Navy said it would take the research into account when reviewing its marine life safety checks for underwater tasks.