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Scorpions are on the march, but researchers have a uniquely Australian solution

In the absence of natural predators such as bilbies, native scorpions are thriving. Photo: La Trobe University
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There are so many scorpions inhabiting parts of arid Australia –an unexpected consequence of losing native species like the bilby – that researchers have suggested bringing back their endangered predators.

Their goal is to restore imbalances in the ecosystem, following concerns that high scorpion numbers may result in reductions in the abundance of some of their prey species.

Researchers from La Trobe University found the key to reducing scorpion populations is in reintroducing native animals such as bilbies.

The arrival of Europeans in Australia introduced predators like feral cats and foxes, which led to large-scale loss of native mammal species.

Research published in Ecology concluded scorpion numbers plummet in the presence of native mammals.

The team also saw a decline in scorpions when mimicking the foraging action of soil-disturbing native mammals.

Mammals also led to a reduction in populations of other invertebrates, such as spiders.

Therefore, repairing ecological damage may involve reintroducing locally extinct digging mammals.

Researchers led by Associate Professor Heloise Gibb found as many as 600 scorpion burrows per hectare in the mammal-free sections of the Australian Wildlife Conservancy’s Scotia Sanctuary in western New South Wales.

It poses the question: “Were they always so abundant or might this plethora of scorpions be the result of wiping out other species from the ecosystem?” Dr Gibb said.

Heloise Gibb in the field. Photo: La Trobe University

“Large native scorpions, up to nine centimetres in length, are really abundant in the Mallee and they play a big role as predators of other smaller, species.”

The Mallee in north-west Victoria can seem “extremely harsh and even lifeless” during summer but it usually comes to life at night with scorpians, geckos, spiders and other nocturnal animals, she said.

Dr Gibb and the team used UV-proof glasses and UV torches to hunt scorpions in the dark on the hottest nights of summer.

“You can’t see much with UV-proof glasses at night. But scorpions fluoresce in the light of our UV torches – so all you can see is scorpions. We used tongs to pick them up by their tails for measurements, because these scorpions are big and nobody wants to be stung.”     

Given the researchers don’t know what Australia’s ecosystems were like 200 years ago, Dr Gibb said reintroducing locally extinct digging mammals is “hard to get right”.

“It’s important to consider that reintroductions may also result in unexpected consequences for ecosystem structure,” she said.

“Over-predation on one species might lead to increases in others and these changes can cascade all the way through from predators to plants.”