What caused it and can it be stopped in the future?

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One ghastly task remains for a rescue team responding to a mass stranding of pilot whales on Tasmania’s west coast: collect and tow some 200 enormous carcasses into the depths of the ocean.

That operation could take place on Sunday, after more than 30 of the whales, which are actually large oceanic dolphins, were successfully saved and taken back to sea during three days of rescues this week.

The effort came nearly two years to the day of Australia’s largest cetacean stranding event involving 470 pilot whales at the same location.

So what could have caused this latest stranding? Why is this place known as a “whale trap”? Could something be done about it, and should we even try?

Why is this part of Tasmania a hotspot for whale stranding?

Pilot whales are not well studied, but they are known to live in pods of 20 or 30 with the females as the leaders. They sometimes form temporary “super herds” of up to 1,000 animals.

Tasmania is known to be a hotspot for cetacean (whale and dolphin) strandings and the area near Strahan’s Macquarie Harbor is particularly known for pilot whale strandings.

Professor Karen Stockin, an expert on cetacean strandings at Massey University in New Zealand, said no one knows for sure why some become “whale traps”, but it is likely to be a combination of prey, how the coastline and the strength and speed of the tides.

“The tide goes in and out very quickly and you can get caught,” he said. “If you are a pilot whale looking for food and you are distracted, they can catch you. That’s why we refer to these places as whale traps.”

Related: Whale strandings: what happens after they die and how do authorities safely remove them?

The deepest waters where pilot whales, mainly squid, live and feed are relatively close to shore around Macquarie Harbor and the gradually sloping Ocean Beach could also be a natural hazard.

Dr. Kris Carlyon, a wildlife biologist with the state’s marine conservation program, was on the scene this week, as he was two years ago.

He said one theory was that the gentle sandy slope toward shore might confuse the echolocation pilot whales use to interpret their surroundings.

What caused this stranding?

Scientists have performed necropsies on some animals on the beach and tissue samples and stomach contents are also being analyzed.

Carlyon said these tests were to rule out possible unnatural causes, but so far the results have suggested a natural event.

“We may never know the exact cause, but we are starting to rule things out,” he said.

Previous investigations of the stomach contents of pilot whales stranded in Ocean Beach found that they were eating a variety of squid.

Carlyon said the prey may have been closer to shore, drawing one or two members of the pod into the natural whale trap.

Stockin said it would be very difficult to know what attracted the whales too much. But whether they were chasing prey or just taking a wrong turn, the herd’s social structure would likely have attracted even more animals.

“What unites pilot whales is that they have strong social bonds that last almost a lifetime with other whales in their group,” he said. “It’s an incredibly strong bond and if you have a lost or weakened animal, there’s a risk that others will try to help.”

Pilot whales can communicate through clicks and whistles, and Stockin said this can make rescuing them difficult, as those still on shore may continually call their podmates for help, forcing them to turn back.

In some mass strandings, Stockin said, if a female who is the herd’s matriarch is still alive but stranded, younger members of the herd might continually return.

She said the fact that this stranding took place two years after the previous main event could suggest a link to a seasonal or cyclical marine heat wave “but there just isn’t enough analysis of these events.”

“We have to remember: mass strandings are a natural phenomenon, but that’s not to say there aren’t times when human-induced strandings happen,” he said.

Could anything be done to prevent this from happening again?

Carlyon said the state’s marine conservation program had considered potential approaches to prevent future strandings, including using underwater sound or developing an early warning system.

“It’s the million dollar question: what can we do to prevent this from happening in the future given that we know this is a massive stranding hotspot?” he said. I don’t have a good answer, to be honest.”

So far, Carlyon said, “there’s nothing that comes to mind as a feasible option,” but the program “will continue to look at whether emerging technology or ideas could help.”

Related: Talking to the whales: can AI bridge the gap between our consciousness and other animals?

Stockin said acoustic emitters are sometimes used to deter some dolphins.

“But there is a very fine line here,” he said. “We don’t want to scare animals away from critical foraging habitat.”

She said that in some places around the world, underwater acoustic monitoring is used to alert authorities to times when marine mammals are in coastal waters.

“Then you might have a higher chance of responding,” Stockin said. “But in our desire as humans to want to fix things, we have to remember that sometimes things are just part of the natural cycle.”

In some indigenous cultures, whale strandings have traditionally been seen as a blessing from the sea. Dead cetaceans are also a food source for coastal and ocean wildlife.

But it was understandable, Stockin said, that humans felt an affinity with cetaceans and wanted to help them, regardless of the cause of their stranding.

“They are not just charismatic megafauna; they have a critical role to play in our oceans,” he said.

“They have dialects in the way that we have accents. Some can even use tools: bottlenose dolphins use sponges in their [nose] to protect themselves when they are looking for food. They have strong social ties. We know that we are dealing here with a society run by women.

“They are complex social mammals like us.”

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