MELBOURNE, Australia — It was a sobering scene: a phalanx of pilot whales, each up to 13 feet long and weighing a little under a ton, lining a remote beach in the Australian island state of Tasmania.
Already, half have died. Those that were still alive rocked back and forth in the shallows of the sand flat, twitching their fins.
On Wednesday, an estimated 230 of the animals were stranded near the town of Strahan on Tasmania’s western coast, just days after at least 14 sperm whales died after beaching on King Island in the Bass Strait, roughly 170 miles to the north.
Wednesday’s beachings came two years to the day after the worst mass whale stranding in Australia’s recorded history, when hundreds of pilot whales perished along roughly the same stretch of sand in Tasmania.
“Because of the waves, they just keep being washed further and further up the beach,” Sam Gerrity, a local boat skipper who also works in the tourism industry, said of the Wednesday strandings. His forecast was bleak. “At least 95 percent will die, because the ocean’s just so fierce,” said Mr. Gerrity, who assisted after the strandings in 2020.
Government experts were heading to the area to plan what they called a complex response to the beachings. Boats from a local fish farm were attempting to pull whales that remained in the sea farther away from the shore. But the growls and clicks of those on the land were beckoning them with a deadly siren song.
Tasmania is a global hot spot for whale strandings. But they remain something of a mystery, said Vanessa Pirotta, a wildlife scientist specializing in marine mammals at Macquarie University. “Every stranding is different, and we don’t know when they’re going to happen,” she said.
That the latest one occurred on the precise date of the 2020 stranding might suggest some environmental factor related to the place or time of year, she said.
But even that is conjecture, she added. Whales that strand might have been led astray by an unwell individual in the group; been thrown off by something in the area, like an unexpected coastal shelf; or simply have been startled by something in the water.
Pilot whales — technically a kind of large dolphin — ordinarily move in groups of up to about 50. But pods of a few hundred are not unheard-of, and it was possible that they had all been traveling together, Dr. Pirotta said. If one whale veers disastrously off course, it may spell doom for hundreds of others.
“Because they are so social,” Dr. Pirotta said, “it’s a follow-the-leader situation.”
In 2020, around 110 of the 470 whales were saved, while many of those that died were pulled out to sea, to decompose away from the shore. This time, the location of the stranding, as well as unpredictable weather and waves of up to 50 feet, will complicate the rescue. More whales were expected to die overnight.
Dealing with their carcasses may be even more difficult. In a couple of days, Mr. Gerrity said, the remains will begin to burst, complicating the disposal.
Mass graves, which have been used on previous occasions, also present problems. As a whale breaks down, it can leach both oil, which can be harmful to other wildlife, and fluids, which attract creatures like sharks, making the beach dangerous for swimmers.
If there is any silver lining from mass strandings, Dr. Pirotta said, “the information that we can acquire from the animals that have died will contribute to science.”