Could noise pollution be the reason for the mass stranding of pilot whales on Orkney?

Scientists  probing a mass stranding of whales are looking at whether sonar or other acoustic disturbance could have led to the tragic event.

A pod of 77 pilot whales died after washing ashore on a beach in Orkney.

It happened almost exactly a year after another large stranding of long-finned pilot whales on the Isle of Lewis.

It is known that in both events seismic surveys for offshore windfarms were being conducted off the islands.

Dr Andrew Brownlow, director of the Scottish Marine Animal Stranding Scheme, said mass strandings of this scale are becoming more common in Scotland - and we need to know why.

He his team were seeking answers over what acoustic activity may have been happening off Orkney.

‘Pilot whales can form very large groups, superpods of many tens, when they are subject to disturbance such as noise or the threat of killer whales,’ he said.

‘We want to know what acoustic activity was taking place in the hours and days before this latest stranding. 

Man has made our oceans noisier and these activities are having an affect - so we need to get a better understanding at what’s happening and the impact on creatures like whales.’

Dr Brownlow added that he was still awaiting information from an acoustic buoy that may contain vital clues over last year’s mass stranding at Tolsta Beach on the Isle of Lewis.

Then an entire pod of 55 pilot whales died. Only 15 were alive when they were washed ashore. One was successfully re-floated while the rest had to be euthanised.

A large pod of pilot whales stranded in July, 2011, at the Kyle of Durness, Sutherland, in what was then believed to have been Scotland’s largest ever such event. 

Some 19 of the 70 whales died.

Four large bombs exploded underwater by the Royal Navy were later blamed by government scientists for the mass stranding.

It is also thought that the sonar waves can frighten deep-diving whales, forcing them to surface too quickly and leading to symptoms similar to decompression sickness, also known as the bends, in humans.

But a spokesman for the MoD has said the Navy does all it can to ensure sonar is not damaging marine life.

Dr Brownlow added: ‘It used to be quite unusual to have a mass stranding event, certainly of this size on Orkney.

‘But over the last ten years or so we have seen an increase both in the number of mass stranding events around Scotland and also the size of the mass and the number of animals that it involves.

‘So that is slightly concerning and that might be because there are just more animals out there, or it could be that there are more hazards that these animals are exposed to.’

In the latest incident, the British Divers Marine Life Rescue (BDMLR) had established 12 of the animals at Tresness Beach on the island of Sanday were still alive when they came out of the water.

However, the decision was taken to euthanise them after refloating efforts failed.

The pod included male whales up to 22ft long as well as females, calves and juveniles.

Members of the public are being asked to stay away from the area as post mortem examinations are carried out.

Experts from the BDMLR, the Scottish SPCA and marine vets from the Scottish mainland travelled to Sanday to assess whether any of the whales could be saved.

The whales needed to be moved back into an upright position as quickly as possible if there is to be any chance of saving them.

Rescuers attempted to keep the whales alive by pouring sea water over them, but the decision was later taken to euthanise them.

A spokesperson for Orkney Islands Council said discussions were taking place on how best to dispose of the bodies.