The Macabre Science of Animal Mass Die-Offs

Unfolding right now across swaths of Australia is an ecological catastrophe, as massive, turbo-charged fires reduce whole landscapes to nothingness. Tens of thousands of koalas had no way of escaping. Livestock lie dead in fields. Innumerable animals have perished, with many species likely pushed to extinction. The few survivors could well starve or fall victim to predators.

We’ll never know the true toll of this mass mortality event, or MME as scientists call it, but we know this: The cadavers that litter the Australian landscape are now rotting, kicking off a cascade of ecological consequences and potentially imperiling human health.

As a field, the experimental study of MMEs is quite new. Sure, researchers can scrutinize a mass die-off in the wild, for instance when a bacterial outbreak killed 200,000 saiga antelopes in central Kazakhstan in 2015. But without meticulously surveying the environment just before the event, any comparison is inherently limited. To do a controlled experiment, you’d either have to source and distribute hordes of carcasses yourself or somehow learn to predict an impending mass death.

One team of researchers has found a clever workaround to the problem, using a subject no one will miss: feral pigs. Mississippi State University ecologist Brandon Barton, forensic entomologist Abby Jones, and environmental microbiologist Heather Jordan set up plots of land and take stock of their ecosystems: the nutrients and microorganisms in the soil, insects, vegetation, and more. Cameras and microphones capture the movements of animals stalking the lands. Then it’s time for the swine.

Feral pigs have become an invasive menace in the US, breeding like crazy and tearing through ecosystems. Trappers nab them, kill them, and send them to Barton and Jones. The team then delivers them to their test plots, distributing some 15 tons of pig carcasses (about 200 individuals of varying sizes) over the course of a day.

dead cow with flies on it
Photograph: Brandon Barton/Mississippi State University

While they’re still fairly fresh, dealing with the carcasses is comparatively easy. Returning daily for two weeks, as the stench grows more brutal and penetrating by the day, that’s the perilous bit. “We took a lot of precautions with gallons of Purell and soap and water and protective equipment, but you still are dealing with a lot of wild animals that are harboring who knows what,” says Barton.

Maggots, for one—rivers of maggots. These infant flies play a pivotal role in the way nature recycles dead animals: They eat decaying flesh, converting it into their own tissue. They took a liking to the pig carcasses in such numbers, they formed great squirming mats on the ground. “It was one of the most incredible things I’ve ever experienced,” says Barton. “Just seeing this carpet of writhing maggots going through the forest and you think, that’s gross. And maybe it is, but those guys are basically little packets of nutrients.”

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