Were tragic whales driven to their death by a sudden NOISE?
After a 77-strong pod died and strandings become more common, scientists ask…
SCIENTISTS investigating a mass stranding of whales are looking at whether sonar or another acoustic disturbance could have led to the tragic event.
A pod of 77 pilot whales died after washing ashore on a beach in Orkney on Thursday.
It happened almost a year after a large stranding of long-finned pilot whales on the Isle of Lewis. It is known that on both occasions seismic surveys for offshore windfarms were being conducted off the islands. This process involves firing pulses of high frequency sound waves at the seabed. Dr Andrew Brownlow, director of the Scottish Marine Animal Stranding Scheme, said strandings of this scale are becoming more common in Scotland and it is vital to know why. He and his team are now seeking answers over what acoustic activity may have been happening off Orkney. Dr Brownlow said: ‘Pilot whales can form very large groups – superpods – when they are subject to disturbance such as noise or the threat of killer whales. We want to know what acoustic activity was taking place before this stranding.
‘Humans have made our oceans noisier and these activities are having an effect, so we need to get a better understanding of what’s happening and the impact on creatures like whales.’
Dr Brownlow said he was still awaiting information from an acoustic buoy that may hold vital clues to last year’s mass stranding at Tolsta Beach on Lewis.
A pod of 55 pilot whales died there. Only 15 were alive when they were washed ashore. One was successfully refloated while the rest had to be euthanised.
A large pod of pilot whales also became stranded in July 2011 at Kyle of Durness, in Sutherland. Nineteen of the 70 whales died while the others managed to get back out to sea at high tide.
Four large bombs exploded underwater by the Royal Navy were later blamed by government scientists for the stranding.
It is also thought 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.
The Ministry of Defence has said the Navy does all it can to ensure sonar does not harm marine life.
Dr Brownlow added: ‘It used to
be unusual to have a mass stranding. But over the last ten years or so we have seen an increase in the number of strandings and the number of animals involved.
‘That is concerning and might be because there are just more animals out there or it could be they are exposed to more hazards.’
In the latest incident, the British Divers Marine Life Rescue (BDMLR) charity found that 12 of the 77 whales at Tresness Beach on the island of Sanday were alive when they came out of the water.
However, the decision was taken to euthanise them after refloating efforts failed. The public is being asked to stay away while post-mortems take place. Dr Brownlow said vets will ‘look to see if there’s any evidence of damage to the hearing cells in the ears of these animals, which might suggest they’ve been exposed to high or prolonged levels of underwater noise’.
Meanwhile, rescuers were yesterday battling to save a minke whale stranded near a beach at Broadford on the Isle of Skye.
BDMLR said: ‘The animal is clearly in distress. It has been thrashing about so is difficult to get close to. It is on its side and is about four metres long. We will keep monitoring the situation.’