Design Science

Fossil poo contains evidence Tassie devils could be returned to the Australian mainland

More than 3,000 years after the predator disappeared off the mainland, evidence of how it co-existed with other animals has been unearthed in its fossilised poo.

ABC News – Science by Genelle Weule

Key points

  • Fossils provide evidence of where Tasmanian devils lived in mainland Australia and how they co-existed with other animals
  • The fossil evidence shows they were a lot more adaptable than previously thought
  • Scientists say the study adds substantial weight to the idea of reintroducing devils to mainland Australia in controlled trials

The windswept dunes of Willandra Lakes in outback New South Wales are vastly different to the wooded forests of Tasmania.

But Tasmanian devils once scampered across this semi-arid landscape in the days before dingoes arrived.

More than 3,000 years after the predator disappeared off the mainland, evidence of how it co-existed with other animals has been unearthed in its fossilised poo.

Michael Westaway hoped the findings, reported in the journal Biological Conservation, would convince conservationists and governments to trial the reintroduction of Tasmanian devils on the mainland.

“Looking at the fossil record shows [devils] were a lot more adaptable than we think,” said Dr Westaway of Griffith University.

“[Devils] interacted with the sort of fauna we see people are trying to reintroduce into the landscape.”

Dr Westaway and colleagues were scouting the ancient lake beds in the World Heritage Area for extinct megafauna fossils, but instead dug up hundreds of bones from much smaller animals.

The bones were from animals such as the burrowing bettong, which is now extinct on most of mainland Australia, bilbies and stick-nest rats.

Along with the bones were hard chunks of fossilised poo, known as coprolites, laced with animal remains.

“There was lots of evidence of burrowing bettongs and the carnivore that was pursuing them down their burrows,” Dr Westaway said.

The size and shape of the poo indicated it came from a devil not a Tasmanian tiger, the only other top predator on the mainland at the time.

“So the [devils] are just chewing through these animals, digesting them, consuming their bone and shooting them out the other end.”

The Willandra fossils indicated devils and other small animals co-existed for 30,000 years before dingoes arrived.

During this time, they survived severe climate swings including the peak of the last Ice Age.

“The landscape was probably more like outer Mongolia than western NSW during the last glacial maximum,” Dr Westaway said.

“They were able to co-exist in this fairly harsh habitat, and there was no clear evidence of things slipping into extinction.”

The reintroduction of Tasmanian devils to the mainland has been proposed by some conservationists as a way of tackling feral predators that are decimating populations of small mammals.

But there are major questions around what kind of mainland environments would be suitable for devils, and how they would interact with other predators and fauna.

Along with analysing fossils from the Willandra Lakes area, the team mapped out all the sites where devil fossils had been found across Australia.

“Our understanding of [the devil’s] range today is biased by its distribution in Tasmania,” Dr Westaway said.

“But if you look at the fossil record they’re just essentially everywhere.”

There is enough evidence in the fossil record to justify conducting controlled trials of devil rewilding across a broad range of environments, he added.

“It’s critical that there is some kind of experimentation to see the impact.”

Benefits of rewilding devils

Mike Letnic, an ecologist from the University of New South Wales who was not involved in the study, has long proposed trialling devils in dingo-free areas on the mainland.

“We need to be bold and give it a go somewhere, even if we do it under very controlled conditions it would be great to see how devils perform on the mainland and how devils perform with foxes,” Professor Letnic said.

He said the new study by Dr Westaway highlighted gaps in modelling his team had previously done.

“This study shows devils are pretty flexible and there’s a chance they can live in a much greater range of environments than we initially put forward.”

“They’ve also provided some really hard data on the types of things devils were eating in mainland Australia.”

While burrowing bettongs were on the devil’s menu, predators were part of a healthy ecosystem, especially predators that the animals evolved with, said Professor Letnic.

“We have this awful view of predators because foxes and cats have done so much damage,” he said.

“The devil is probably at the right level for our native animals.”

But proceed with caution

Michael McCarthy, a conservation biologist at the University of Melbourne who was not involved in the study, broadly supports the idea of trials if they are done under strict conditions.

“All the evidence is that devils on the mainland would be a really positive benefit both for the devils … and the diversity of the mammals and some birds,” Professor McCarthy said.

He said the new study provided some reassurances that devils could survive on the mainland and co-exist with small mammals.

But, he added, the genetic make-up of today’s devils may be different so it was unclear whether devils sourced from Tasmania could adapt to the same range of environments.

Experiments would also need to factor in the impact of changes to the environment since devils lived on the mainland.

“The biological environment, the physical environment, the habitats are a lot more fragmented, we’ve got different complements of species including invasive species.”

“By reducing the pressure of cats and foxes these small mammals might be able to flourish, but at the same time they may come under more pressure from predation,” Professor McCarthy said.

One thing is certain: trialling the reintroduction of Tassie devils onto the mainland would be a mammoth task.

“That’s going to take a lot of work, it’s going to be really expensive to do it in a way that is reversible where you can get the devils out and on a spatial scale that is sufficiently large,” Professor McCarthy said.

“It’s a big undertaking, but potentially beneficial.”

Primary image: Devils co-existed with many small mammals across the Australian mainland for thousands of years before dingoes arrived. (Supplied: Devil Ark)

Source: Fossil poo contains evidence Tassie devils could be returned to the Australian mainland – Science News – ABC News