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

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

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A gruesome task remains for a rescue team responding to a mass stranding of pilot whales on Tasmania’s west coast – scooping up and towing around 200 huge carcasses out to the deep sea.

That operation could take place on Sunday, after more than 30 of the whales – which are actually large bottlenose dolphins – were rescued and returned to the sea during three days of rescues this week.

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

So what could have caused this latest stranding, why is this place known as a ‘whale trap’ and can anything be done about it – and should we even try?

Why is this part of Tasmania a whale stranding hotspot?

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

Tasmania is known to be a hotspot for cetacean strandings – whales and dolphins – and the area near Strahan’s Macquarie Harbor is particularly famous for pilot whale strandings.

Prof Karen Stockin, an expert on cetacean strandings at Massey University in New Zealand, said no one knew for sure why some became “whale traps”, but it was likely a combination of prey, the shape of the coastline and the strength and speed of the tide.

“The tide comes in and out very quickly and you can get caught out,” she said. “If you’re a pilot whale searching and you’re distracted, you can get caught. That’s why we refer to these places as whale traps.”

Related: Whale strandings: what happens after they die and how can the authorities get rid of them safely?

The deeper waters where the pilot whales live and feed – mostly on squid – are relatively close to the coast around Macquarie Harbour, and the gradually sloping Ocean Beach can also be a natural hazard.

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

He said one theory was that the gentle sand slope towards the shoreline could confuse the echolocation that 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 suggest a natural event.

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

Previous studies of the stomach contents of pilot whales stranded on Ocean Beach found that they ate a variety of squid.

Carlyon said it is possible the prey may have been closer to shore, pulling one or two pod members into the natural whale trap.

Stockin said it would be very difficult to know what drew the whales too close. But whether they were chasing prey or just taking a wrong turn, the social structure of the pod would likely have drawn in even more animals.

“What binds pilot whales together is that they have strong social bonds that last almost a lifetime with other whales in their group,” she 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 more difficult, as those still on land can continually call podmates for help, forcing them to return.

In some mass strandings, Stockin said, if a female who is the pod’s matriarch is still alive but stranded, junior pod members can continually return.

She said the fact that this stranding occurred two years to the day after the previous major event may suggest a link to a seasonal or cyclical marine heat wave “but there’s just not 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 strandings occur that are human-induced,” she said.

Can anything be done to prevent this from happening again?

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

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

So far, Carlyon said, “there’s nothing that jumps out at us as a possible option”, but the program will “continue to see if new technologies or ideas can help”.

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

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

“But there’s a very fine line here,” she said. “We don’t want to scare animals away from critical feeding 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 better 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 whales are also a food source for coastal and marine animals.

But it was understandable, Stockin said, that humans felt a kinship with whales and wanted to help them — regardless of what caused their stranding.

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

“They have dialects the way we have accents. Some can even use tools – bottlenose dolphins use sponges on themselves [nose] to protect themselves when searching. They have strong social ties. We know we are dealing with a female-led society here.

“They are complex social mammals like us.”

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