The anniversary of Australia’s biggest mass pilot whale stranding has been marked by a repeat event, with experts admitting they are baffled by the heartbreaking phenomenon.

On Wednesday, a pod of 230 pilot whales stranded on Tasmania’s Ocean Beach, near Macquarie Harbour.

By Thursday afternoon, as a massive community-wide rescue effort continued, only 35 whales were still alive.

By Thursday night, 32 had been refloated and pushed out into deeper waters, but rescuers remained uncertain they would survive.

“We can hear them calling and communicating to one another. We do know we have success in these efforts, and that’s what keeps driving us,” one tired rescuer told the ABC.

The deadly event follows the discovery of 14 dead sperm whales on Tasmania’s King Island on Monday.

The mass deaths came just a day before the second anniversary of Australia’s biggest stranding on record, which left 470 long-finned pilot whales beached inside the same harbour in September 2020.

Strahan mayor Shane Pitt told the ABC that Ocean Beach was closed to the public while wildlife authorities tried to rescue the remaining whales. It would remain shut for the clean-up after the “devastating” event.

“I haven’t heard at this stage whether there has been success in any of the operations so far, but hopefully, fingers crossed, we do see some recovery of some of the whales that are still alive,” he said.

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Wildlife authorities are still in the dark about what is leading the whales to their deaths.

Wildlife scientist Vanessa Pirotta told The New Daily there likely won’t be answers for a long time – or maybe ever.

“We know that whale strandings are a mystery; we don’t exactly know why they happen,” she said.

“But what we do know in this case, is that we’ve had a mass stranding event again, similar location, same time of year.

“Is there something environmental happening? Or is this just a coincidence?”

Although authorities were likely to perform necropsies (animal autopsies), there will be so much information to gather, from toxins to issues with diet, that it might be impossible to pinpoint anything that offered a clue to why the animals were driven to Tasmanian shores, Dr Pirotta said.

The whales may also have mis-navigated, had issues with their social interactions, or followed initially stranded pod members to their own deaths.

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Following the 2020 mass stranding, then-Monash University research associate David Hocking referenced research that suggested gently sloping sandy beaches could reflect echolocation clicks away from the animal that produced them.

That might confuse whales into thinking the area ahead is open water.

Strong familial and social bonds could then spell doom for the whole pod, since whales tend to rush to help each other.

They are also likely to turn around after being rescued and become stranded again, in a forlorn attempt to help their pod members.

Unlike humpback whales, pilot whales don’t have a predictable migration pattern, making it difficult for researchers to keep track of their numbers, habits, and any information that might answer why they are consistently stranding themselves en masse.

“In this case, strandings are a completely a random event,” Dr Pirotta said, “and we don’t as humans know why, how or when these events are likely to happen.”