Scorpions Taking Over Parts of Australia With 600 Burrows Per Hectare, Scientists Find

Scorpions have been thriving in parts of Australia, with the loss of predators allowing them to take over some of the country's sandy landscapes, a new study has found.

In some of the arid regions studied, researchers discovered up to 600 scorpion burrows per hectare.

Scientists, from the Department of Ecology, Environment and Evolution, School of Life Sciences at La Trobe University, Australia, were assessing scorpion populations in order to work out the long-term effects of the arrival of Europeans on endemic wildlife in ecosystems in the country.

Around 100 species have gone extinct in Australia over the last 200 years, with cats and foxes driving out dozens of native mammals, according to a separate study published in the Proceedings of the National Academy of Sciences in 2015.

To understand the impact of these losses, the team carried out surveys at two sites—one in the arid northern part of South Australia, and a semi-arid region in New South Wales.

They were looking at how the reintroduction of certain mammal species had affected predatory invertebrate numbers in dry regions.

"Were they always so abundant or might this plethora of scorpions be the result of wiping out other species from the ecosystem?" Co-author Heloise Gibb said in a statement.

"Large native scorpions, up to 9 cm (3.5 inches) in length, are really abundant in the Mallee and they play a big role as predators of other, smaller, species."

The findings, published in the journal Ecology, suggest that the massive loss of native mammal species when Europeans first arrived helped scorpion numbers increase.

In the presence of mammals their populations plummet, the study found. In experiments where the team disturbed the soil, in order to mimic native mammals, scorpion numbers also fell.

australia scorpion
Stock image of a scorpion in Australia, where researchers have found the lack of predators has allowed their numbers to increase significantly. iStock

Researchers say the results are important if authorities are going to try to restore habitats to what they were over two centuries ago. "Reintroducing locally extinct digging mammals provides an opportunity to restore ecosystems, but it's hard to get right because we don't know what Australia's ecosystems were like 200 years ago," Gibb said.

"It's important to consider that reintroductions may also result in unexpected consequences for ecosystem structure. Over-predation on one species might lead to increases in others and these changes can cascade all the way through from predators to plants."

'Little things that run the world'

The study concluded that it is unclear whether re-introducing lost mammals to these arid regions of Australia would reconstruct the pre-European set-up or create an entirely new one. The researchers said that understanding impacts on other species, including insects, is hugely important.

"In the absence of sound knowledge of historical population densities, it is critical that we carefully track the impacts of threatened species reintroductions on ecosystems and do not neglect the 'little things that run the world,'" they wrote.