Rotting feral pig carcasses teach scientists what happens when tons of animals die all at once, as in Australia's bushfires
Posted by admin on 10th January 2020

The unprecedented wildfire raging across Australia is not only destroying human lives, but has killed hundreds of millions of animals – perhaps billions before it is all over.

Burning is not the only cause of death in this catastrophe. Many animals have outrun the flames only to die in fences and roads by the thousands. Others may live, for now, but, without their homes, food and water, are likely to succumb to the elements soon.

Unfortunately, animal die-offs of massive proportions are becoming more frequent. Global change – which includes human-caused changes in climate, land use, fire regimes and other things – may largely be to blame for the increased frequency and intensity of mass mortality events across all kinds of animals.

This was the case in 2015 when unseasonably warm and humid weather allowed a normally benign bacteria to wipe out 200,000 saiga antelope in Kazakhstan in just a few weeks. Similarly, a single lightning strike killed 323 reindeer in 2016, and another 200 starved last year at once after unseasonable rain left an impenetrable layer of ice covering their food. And, for five years in a row, tens of thousands of starved sea birds have washed up in Alaska. These are just a few recent examples.

So, what happens when everything dies all at once?

An experimental approach to die-off events

Our research group studies the ecological consequences of mass mortality events – MMEs for short.

Studying MMEs is difficult because they are unpredictable and can occur anywhere around the world, making it logistically challenging to study the actual events. Even if we could hop on a plane and travel to a distant mass mortality event quickly, we wouldn’t have data on what the ecosystem was like before, so drawing conclusions would be nearly impossible.

To overcome this hurdle, we have worked with wildlife biologist Marcus Lashley and David Mason at the University of Florida to take on the dirty task of simulating mass mortality events in large experiments with thousands of pounds of carrion.

Trappers donated nearly 15,000 pounds of feral swine carcasses to simulate mass mortality events in Oklahoma in 2019.
Brandon Barton, Mississippi State University, CC BY-ND

In spring 2019 we began our largest experiment to date, deploying nearly 15 tons of carcasses in Oklahoma. Our first challenge was finding a large – and ethical – source of carcasses. We partnered with professional trappers who were removing feral pigs, an invasive species that has potential to damage crops, spread disease and negatively affect wildlife. These wild boar were trapped for conservation purposes. Rather than having their carcasses go to waste, we were able to put them to good use.

We wanted to see how increasing amounts of carrion affect decomposition in ways that may alter ecosystems or promote the spread of pathogens. Before the carcasses arrived, we identified plots and sampled the initial soil, microbes, plants, insects and wildlife. This provided important baseline information that wouldn’t be available during a real-world mass mortality event.

The real work began after the carcasses arrived. Pigs have a stinky reputation for a reason, and feral swine – especially several tons of dead ones – are not a pleasant sight or smell. We carefully placed each carcass, which averaged about 70 pounds, in the predetermined plots. Some plots received a single pig to represent a “normal” death event; others received 10 carcasses to represent an MME.