What happens after they die and how do the authorities dispose of them safely?

Two massive strandings in Tasmanian waters in one week have left nearly 200 pilot whales and 14 sperm whales dead.

On Monday, 14 juvenile sperm whales died and washed ashore on King Island in Bass Strait. About 230 pilot whales were stranded on Ocean Beach, west of the Tasmanian town of Strahan, on Wednesday.

Tasmanian authorities said on Thursday they would transition to “body recovery and disposal operations” in the coming days. But how to safely get rid of the huge beasts?

What happens to animals after they die?

If cetaceans are left on shore where they stranded and died, their decomposition can pose a biohazard risk, said Dr. Olaf Meynecke, of Griffith University’s Center for Coastal and Marine Research. “Removing animals is a major problem and something that we forget about once a rescue mission is over.”

Related: ‘Audio tattoos’: Sperm whales use sounds to signal their social identity, scientists say

In warmer climates, the internal decomposition of dead whales can lead to spontaneous explosions. The intestinal bacteria of whales can multiply rapidly and produce large amounts of methane gas. “If the rest of the body is still intact, if the outer layer, the fat, is still intact and not broken down, then it can cause an explosion,” Meynecke said.

In 2004, the decomposing carcass of a 60-tonne, 17-meter sperm whale exploded on a busy street in the Taiwanese city of Tainan, “filling cars and shops with blood and organs and stopping traffic for hours.”

The researchers would likely conduct checks on the recently stranded animals, including necropsies to look at their gut contents and assess general health indicators, such as the thickness of their blubber layer, Meynecke said.

Necropsies usually can’t be done more than a few days after a whale has died because of the risk of explosion, he says. “It’s actually part of the risk assessment … the animal needs to be evaluated beforehand and if there are signs of swelling in the intestinal area, the pressure needs to be released later on.” [of the necropsy].”

“If there is any benefit, it is that dead individuals will be an opportunity to contribute to science,” said Dr. Vanessa Pirotta, a wildlife scientist affiliated with Macquarie University, who described it as the silver lining of a sad situation. .

“We can learn more about their diet, their genetics, how similar these individuals were to the population that was stranded earlier,” he says, referring to a 2020 mass stranding event at the same location, in which 350 pilot whales died.

How to get rid of a dead whale?

Cetaceans that die on land after beaching must be towed out to the ocean, Meynecke said. “They should be returned to the sea, that’s where they belong.”

Sam Gerrity of Southwest Expeditions has been involved in the logistics effort after the most recent and 2020 mass strandings near Strahan. He said the removal involved a “quite confrontational” process of towing dozens of carcasses out to sea.

Open-air decomposition and burial were tried after the 2020 pilot whale stranding, but officials have said they are not the preferred methods for the more recent stranding. “Our first option will be to get the carcasses to the depths of the ocean,” Incident Controller Brendon Clark said at a news conference on Thursday.

But the logistics for the largest whale species are much more complicated than for pilot whales, which weigh up to three tons. “[For a sperm whale] we’re looking at probably more than 15 tons or more. Once they’re no longer in the water, they become too heavy to drag with normal gear,” Meynecke said.

Burying whales should be avoided, he said. “Disposing of a marine animal on land is generally not a good idea. Animals will decompose much more slowly 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, then excavated it a week later, due to community concerns about increased shark activity.

“If it has a connection to the water table, there’s a chance it could seep into the ocean; it might attract predators, but… that’s not fully proven,” Meynecke said.

An infamous case of whale disposal occurred in the US in 1970, when the Oregon Division of Highways 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 large chunks of whale blubber fell everywhere,” said a reporter in a now-viral television story.

Meynecke called the incident “proof of human stupidity. We laugh about it, but it’s the same as burying something: just because we can’t see it, it doesn’t mean it’s gone, and just because we blow it up doesn’t mean it’s gone, it just spreads out into smaller pieces and creates more problems. ”.

What caused the massive whale strandings?

It is still not entirely clear why mass strandings of whales occur. Pilot whales, misnamed because they are actually a large oceanic dolphin, are known as the species most susceptible to mass strandings, because they are very social and form pods of several hundred.

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

“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 really know each other and the calls don’t make sense to them.” She compared it to the panic among humans at a concert or other crowd. “There is that emotional stress that actually drives them to continually rechain themselves.”

However, sperm whales don’t usually beach themselves en masse, and the deaths of more than a dozen on King Island were concerning, Meynecke said.

“It’s 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 is also what was linked to the stranding of sperm whales in Europe in 2016.”

That incident was related to changes in water temperature and the movement of food sources into shallower waters in the North Sea. “We could see more of these strandings in the future,” Meynecke said.

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