Two mass strandings in Tasmanian waters in one week have left around 200 pilot whales and 14 sperm whales dead.
On Monday, 14 young sperm whales died and washed ashore at King Island in Bass Strait. Around the rain 230 pilot whales was washed ashore on Ocean Beach, west of the Tasmanian town of Strahan on Wednesday.
Tasmanian authorities said Thursday that they would move into “carcass recovery and disposal operations” in the coming days. But how do you safely dispose of the massive beasts?
What happens to animals when they die?
If whales are left on land where they are stranded and dead, their decomposition can pose a biohazard risk, said Dr. Olaf Meynecke, from Griffith University’s Coastal and Marine Research Centre. “The removal of the animals is a big problem and something that we kind of forget when a rescue mission is over.”
In warmer climates, the internal decomposition of dead whales can result in spontaneous explosions. Intestinal bacteria in the whales can multiply quickly and produce large amounts of methane gas. “If the rest of the body is still intact — if the outer layer, blubber, is still intact and not broken up — then that can lead to an explosion,” Meynecke said.
In 2004, the decomposing carcass of a 60-ton 17-meter sperm whale exploded on a busy street in the Taiwanese city of Tainan, “cars and shops are showered with blood and organs, stopping traffic for hours”.
Scientists would likely conduct checks on the newly stranded animals, including necropsies to look at gut contents and assess overall health indicators such as the thickness of their blubber, Meynecke said.
Normally, autopsies cannot be done more than a few days after a whale dies, because of the danger of explosion, he says. “It’s actually part of the risk assessment … the animal needs to be assessed beforehand and if there’s any evidence of swelling in the gut area, the pressure needs to be released ahead [of the necropsy].”
“If there is any benefit, it is that the dead individuals will be an opportunity to contribute to science,” said Dr. Vanessa Pirotta, a wildlife researcher associated with Macquarie University, described it as a sad situation.
“We can learn more about their diet, their genetics, how similar these individuals were to the population that stranded before,” she says, referring to a 2020 mass stranding event same place where 350 pilot whales died.
How do you get rid of a dead whale?
Whales that die on land after stranding should be towed out to sea, Meynecke said. “They should be returned to the sea – that’s where they belong.”
Sam Gerrity of Southwest Expeditions has been involved in the logistical effort following both the recent and 2020 mass strandings near Strahan. He said the disposal involved a “quite confrontational” process of dragging dozens of carcasses out to sea.
Open decomposition and burial were both tried after the pilot whale stranding in 2020, but authorities have said they are not the preferred methods for the latest stranding. “Our first option will be to long-line the carcasses out to the deep sea,” incident controller Brendon Clark said at a news conference Thursday.
But the logistics for larger cetacean species are far more difficult than pilot whales, which weigh up to three tonnes. “[For a sperm whale] we’re looking at probably over 15 tons or more. When they are no longer in the water, they become too heavy to pull with normal equipment,” said Meynecke.
Burial of whales should be avoided, he said. “Disposing of a marine animal on land is generally not a good idea. The animals will decompose much more slowly once they are buried … it will take months and it is a very slow process.”
In 2017, a council in New South Wales buried a 18-ton humpback whale at Port Macquarie’s Nobby’s Beach and excavated it a week later due to community concerns about increased shark activity.
“If you have a connection to the water table, there’s a chance it’s leaking into the ocean — it could potentially attract predators, but … it’s not fully proven,” Meynecke said.
A notorious case of whale disposal occurred in the United States in 1970, when the Oregon Highway Division tried to get rid of a rotting sperm whale by blowing it up with dynamite.
“The humor of the whole situation suddenly gave way to a race for survival as huge chunks of blubber fell everywhere,” said a reporter in a now-viral TV story.
Meynecke called the incident “proof of human stupidity. We laugh at it, but it’s the same as burying something – just because we can’t see it doesn’t mean it’s gone, and just because we blow it up, doesn’t mean it’s gone – it’s just being distributed in smaller pieces, and that creates more problems.”
What caused the great whale strandings?
Why massive whale strandings occur is still not entirely clear. Pilot whales – misnamed as they are actually a large oceanic dolphin – are known as the most susceptible species to mass strandings because they are highly social and form pods of several hundred.
“They end up in these big groups, but they don’t know each other very well,” Meynecke said. “If one of them starts to panic … there’s a lot of miscommunication because they don’t actually know each other and the calls don’t make sense to them.” He compared it to panic among people at a concert or other crowd. “There’s the emotional stress that actually drives them to continuously re-strand.”
Sperm whales don’t usually beach, however, and more than a dozen deaths on King Island were concerning, Meynecke said.
“It is probably not a coincidence that these two species beached at similar times because they could have been looking for prey closer to the islands,” he said. “We have drastic changes in the marine environment related to climate change. That was also related to stranding of sperm whales in Europe in 2016.”
This event was associated with changes in water temperatures and movement of food sources to shallow waters in the North Sea. “We may see more of these strandings in the future,” Meynecke said.