Orkney whale stranding: Post mortem to check if hearing damage led to tragedy

Dr Andrew Brownlow, director of the Scottish Marine Animal Stranding Scheme, which is based at Glasgow University, said colleagues were working against the clock to retrieve as much information as possible before decomposition set in.

Full post-mortems had been carried out on more than 20 of the animals with tissue samples taken from all 77 whales to determine factors such as contaminants, toxins and genetics.

He said ears had been taken from six older females - “the oldest, most precious animals” - given they are at the head of the pod which other members follow.

Damage to hearing can be caused by explosives and sonar equipment used by the military to detect submarines as well as both the renewables and oil and gas industries.

Dr Brownlow, who added that removing the ears was an extremely difficult task given their location deep within the skull, said: “By looking at the ears we can potentially try to understand whether these animals have been exposed to significant amounts of underwater noise and basically if they are deaf.

“These are animals that use sound to navigate, to forage and communicate and basically all the life processes that we would use sight for.

“If their hearing is damaged that can have a massive impact. They are incredibly tight-knit communities so if one animal gets into trouble and goes off in a particular direction, the others tend to follow.

“The ears will give us some insight into significant noise . We won’t know if the animals were scared, if there were behavioural changes or if they were running away from something they were worried about such as killer whales, underwater noise or military activity or sonar.

“What we are looking for is significant damage from things like long and protracted exposure to noise, things like exposure to underwater explosives, exposure to military sonar and particularly military sonar that is used to try and find enemy submarines, that seems to be in the frequencies that will do this.

“Basically we are talking about any impulsive noise that is put into the marine environment.

“If - and it is a big if - these animals were close enought to the source of that noise then that would cause some difficulty but I don’t think we are dealing with physical trauma, I think what we are seeing is a behavioural response.”

Dr Brownlow said a request had been made to the Ministry of Defence for any information on activity in the area.

Pilot whales are usually found around 100 kilometres out into the North Sea.

Despite their presence in Scottish waters, they remained “very cryptic animals,” he added.

“It is remarkable how little we know about them about their standard ecology and that is a big problem

“Because we don’t fully understand some really basic stuff about these populations, such as where they are, what they are feeding on and how they are moving, how the impact of climate change is impacting them, we can’t make decisions about how to prevent them from happening again.”