Lewis whales: Call for investigation into why pod was there

Forty of the 55 had been dead even when they were first discovered, and despite valiant efforts by volunteers from British Divers Marine Life Rescue only one was successfully enough refloated to be saved.

It was, said Dr Brownlow, the most animals SMASS has ever had to process in one post-mortem. “To put it into context,” he said, “we’ve had the same number of cetaceans to post-mortem in this past week as we would normally have in a year.”

He made his call at it emerged more than 50 whales of the same species have died in a mass stranding event in Western Australia.

The team of experts working on Lewis quickly formed a theory about why the whales had stranded. One of the females had been giving birth, and possibly had got in trouble, and, as pilot whales are highly social mammals, the rest of the pod had probably surrounded her to support her.

Since the topography of Traigh Mhor at Tolsta, Lewis – a shallow, sandy, surfer’s beach, with a tide that goes out very quickly – is particularly dangerous, a “whale trap”, when the water went out they then found themselves inhaling surf and sand.

“The surf,” said Dr Brownlow, “is particularly hazardous because the water breaks over their blowhole and that means they can quickly drown. Once they had ended up on that beach a set of processes were put in place which led to so many dying.”

But a bigger question of why they were in those waters at all has yet to be answered.

Long-fin pilot whales are, Dr Brownlow pointed out, a deep water species, very uncommonly seen in that particular stretch of water. “There are,” he said, “decades of citizen science sightings data collected at Tiumpan Head- just to the north of that beach- by Hebridean Whale and Dolphin Trust and Whale and Dolphin Conservation, and they have fewer than a handful of confirmed pilot whales sightings - only 4 sightings since 2011 and none recently."

 The pod of pilot whales stranded at Traigh Mhor. Image: Mairi Robertson-Carrey/Cristina McAvoy/BDMLR/PA Wire

Two types of forces might, he added, have led the whales into such waters. One is the pull towards something – for example the pull of prey.

“But,” he said, “it doesn’t seem to be the case that they were following prey. These animals hadn’t been feeding recently, so it wasn’t like they had come into an area because they were following fish or squid”

Another is a push – they were moving away from something. “Did something happen further out to sea that has pushed them into the inshore waters?” said Dr Brownlow. “That could be human or natural. It could be avoiding predators, such as killer whales, or that the weather was terrible and they decided to seek shelter. But it could also be the impact of human activities. And clearly one of those activities which is most likely to do this is the impact of underwater noise.”

READ MORE: Lewis whales: 'Most lethal mass stranding in living memory'

READ MORE: Stranded whales, Isle of Lewis: ‘It hits you emotionally.'

A 2015 report into the mass stranding of pilot whales at the Kyle of Durness in 2011, for instance, concluded that large bombs exploded underwater by the Royal Navy were to blame.

Dr Brownlow is a veterinary surgeon with background in the epidemiology of terrestrial animal diseases. His involvement in marine strandings came, accidentally in 2008, when he was in East Africa working on the “interface between cattle and wildlife in various countries”.

His job happened to be in the same building as the organisation running a strandings scheme, and “when a sperm whale threw itself onto the beach” he found himself down here.

As grim and unpleasant as the necropsies he undertakes are, he sees them as an opportunity ”to ask questions about population and marine health, which are important for all of us.”

During the long, arduous SMASS post-mortem, which took place at a landfill on Lewis, the team, which gathered from across the UK and Europe, collected copious, amounts of samples. “We’ve got data," he said, "from all 55 animals, and examined all 54 animals that died.”

Among those samples was a small number of ears, which might give some indication of whether the whales had been impacted by noise. “Unfortunately,” Dr Brownlow said, “we weren’t able to get many ears. You need to do it within a few hours of the animal dying because otherwise it’s hard to distinguish auditory pathology that happened before the animal died and changes after death."

Analysis of the samples and post-mortem, which is Scottish Government funded, will be published when complete.

Dr Andrew Brownlow of the Scottish Marine Animal Stranding Scheme doing a whale necropsy on Lewis

An investigation of the stranding, said Dr Brownlow, would represent an opportunity to look at why the whales were there. It would also enhance understanding of this mysterious species and provide indicators of overall marine health.

He said: “We have and are in the process of increasing the industrialisation of our oceans, and that has an impact on the animals that live within it, but also the wider ocean health. Investigating events such as this give you a window of insight into otherwise very cryptic species, animals that are very difficult to understand and sample by other means.

READ MORE Lewis whales: Rescue operation launched after pod beaches at Tolsta

"If you look at cetaceans in general, they are good sentinel species of wider ecosystem health because they’re long-lived, highly mobile species that bestride ecosystems. So if they’re doing okay probably the rest of the marine ecosystem is doing okay. When we have events such as this it’s important to understand what might have been drivers for it.”

Events like these, he added, should be examined as potential canaries in the coalmine for wider ocean health. “Are there emerging diseases? We know that climate change is changing the risk of disease transmission through our waters. We know that we’re increasing the amount of impulsive noise that’s going out there from a number of different sources and that can be hazardous to these animals.”

“We are talking with Marine Scotland," he said, "about next steps for this investigation and understandably that’s not going to be quick, it’s not going to be cheap, but I think it’s unquestionably worthwhile."

A Scottish Government spokesperson said: “We welcome the important work that the SMASS team is undertaking, and we are in ongoing discussions with them regarding next steps in the investigation.”