Two mass strandings in Tasmanian waters in a week left around 200 pilot whales and 14 sperm whales dead.
On Monday, 14 juvenile sperm whales died and were stranded on King Island in Bass Strait. Around 230 pilot whales washed up on Ocean Beach, west of the Tasmanian town of Strahan, on Wednesday.
Tasmanian authorities announced on Thursday that they would move into “carcass recovery and disposal operations” in the coming days. But how do you safely get rid of massive beasts?
What happens to animals after they die?
If cetaceans are left ashore where they stranded and died, their decomposition can pose a biohazard, said Dr Olaf Meynecke, of Griffith University’s Center for Coastal and Marine Research. “Animal removal is a major issue and something we kind of forget about once a rescue mission is over.”
In warmer climates, the internal decomposition of dead whales can lead to spontaneous explosions. The gut bacteria of whales can multiply rapidly, producing large amounts of methane. “If the rest of the body is still intact — if the outer layer, the fat, is still intact and not broken — 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, “flooding cars and shops with blood and organs and stopping traffic for hours “.
Researchers would likely perform checks on recently stranded animals, including necropsies to examine intestinal contents and assess overall health indicators such as their fat layer thickness, Meynecke said.
Usually, necropsies can’t be done until a few days after a whale dies, because of the risk of explosion, he says. “It’s actually part of the risk assessment…the animal should be assessed first and if there are any signs of swelling in the intestinal area, the pressure should be released forward. [of the necropsy].”
“If there is anything beneficial, it is that deceased individuals will be an opportunity to contribute to science,” said Dr Vanessa Pirotta, a wildlife scientist affiliated with Macquarie University, who l described as the silver lining of a sad situation.
“We can learn more about their diet, their genetics, the similarity of these individuals to the population that stranded before,” she says, referring to a 2020 mass stranding at the same location, in which 350 pilot whales died.
How to get rid of a dead whale?
Cetaceans that die ashore after being stranded should be towed out to sea, Meynecke said. “They should be sent back to sea – that’s where they belong.”
Sam Gerrity of Southwest Expeditions was involved in the logistical effort after the most recent and 2020 mass groundings near Strahan. He said the disposal involved a “quite difficult” process of towing dozens of carcasses out to sea.
Open-air decomposition and burial were both tested after the pilot whales were stranded in 2020, but authorities said they were not the preferred methods for the most recent stranding. “Our first option will be to transport the carcasses to the depths of the ocean,” incident controller Brendon Clark said at a press conference on Thursday.
But the logistics of large species of whales are much more delicate than those of pilot whales, which weigh up to three tons. “[For a sperm whale] we’re probably looking at 15 tons or more. Once they’re out of the water, they become too heavy to drag with normal gear,” Meynecke said.
Avoid burying whales, he said. “Eliminating a marine animal on land is generally not a good idea. Animals will decompose much slower once they are buried…it will take months and it is a very slow process.
In 2017, a New South Wales council buried an 18-tonne humpback whale on Port Macquarie’s Nobbys Beach and then excavated it a week later, due to community concerns about the activity increase in sharks.
“If you have a groundwater connection, there’s a chance it could escape into the ocean – that could potentially attract predators but…it’s not fully proven,” Meynecke said.
An infamous case of whale disposal occurred in the United States in 1970, when the Oregon Highway Division attempted to dispose of a decomposing 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 whale blubber fell everywhere,” a reporter said in a now-viral TV report.
Meynecke called the incident “evidence of human stupidity”. We laugh about 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 that it’s gone – it’s just distributed in smaller chunks and it creates more problems.
What caused the mass whale strandings?
Why mass strandings of whales occur is not yet entirely clear. Pilot whales – misnamed because they are actually an oceanic bottlenose dolphin – are known as the species most susceptible to mass strandings, as they are highly social and form pods of several hundred.
“They hang out 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 misunderstandings because they don’t really know each other and the calls don’t make sense to them.” He likened it to panic among humans at a concert or other crowd. “There’s this emotional stress that also causes them to continually retreat.”
Sperm whales, however, don’t usually wash ashore en masse, and the death of more than a dozen on King Island was concerning, Meynecke said.
“It’s probably not a coincidence that these two species stranded at similar times, as they could have been looking for prey closer to the islands,” he said. “We have drastic changes in the marine environment linked to climate change. This is also what was linked to the stranding of sperm whales in Europe in 2016.”
This incident was linked to changes in water temperature and the shifting of food sources to shallower waters in the North Sea. “We may see more of these strandings in the future,” Meynecke said.