Environmentalists are trying to establish what caused the 33 pilot whales to perish on the County Donegal beach.
Dr Simon Berrow, of the Irish Whale and Dolphin Group, said Royal Navy sonar equipment may have played a role.
‘Thirty or 40 pilot whales were spotted off the Inner Hebrides at South Uist last week,’ he said.
‘It looked like they were going to strand. It was bad weather. They were not seen again.’
Dr Berrow said the Royal Navy had been in the area off the island of South Uist, North West Scotland, in recent weeks, but had moved away.
However, a spokesman for the Ministry of Defence said: ‘The Royal Navy can confirm that they were not in the area using sonar and have not been for some time.’
In the past, the Navy has denied that sonar noise from its warships could cause whales to beach.
However, in America, the U.S. navy was ordered not to use mid-frequency sonar during training exercises from 2007 and 2009, after a judge found in favour of campaigners who argued the devices harmed marine mammals in the area.
A team from the Galway-Mayo Institute of Technology travelled to Donegal over the weekend to see if they could determine what had happened.
Most whales are already sick, malnourished, dehydrated or injured when they become stranded, and many will have experienced weeks of suffering.
Once out of the water, they endure hours of painful muscle damage and kidney failure.
Animal welfare groups, including the RSPCA, believe stranded whales should be humanely put down rather than rescued.
They say there is evidence that the creatures have ‘little or no chance’ of survival once they are trapped on the shore or in shallow waters.
Of 54 whales stranded in Britain between 2002 and 2006, not one survived.
The new policy was announced last year as more than 70 long-finned pilot whales died after beaching themselves on a remote south-west Australian beach.
The RSPCA acknowledged its policy change was controversial but said it had to put the welfare of whales first.
The new approach covers all the major deep sea whales.
Dolphins and porpoises are less vulnerable and will still be rescued. Whales will be killed by a lethal injection once a vet and marine mammal experts have checked the scene.
They are most likely to get a reprieve if they are stranded on the west coast where it is relatively easy for them to get back into deep water.
The North Sea, on the other hand, is known as a ‘whale trap’.
In January 2006, a bottle-nosed whale died in the Thames after it was lifted on to a pontoon ready to be taken back out to sea.
The RSPCA said, with the benefit of hindsight, it may have been better to put the whale down as soon as it was discovered.