How giant lizards in Australia protect sheep

Heath goannas, giant lizards native to Australia, might be saving sheep farmers millions of dollars and could help boost native wildlife according to new research.

Among the largest living lizards in the world, heath goannas (Varanus rosenbergi) can reach lengths of up to 1.5 metres. They are found across the southern part of the Australian continent, but are considered vulnerable in New South Wales and South Australia, and critically endangered in Victoria.

The scavenging lizards act as nature’s clean-up crews, clearing maggot-ridden animal carcasses. This in turn, the researchers found, reduces the emergence of blowflies which lay eggs on the backsides of sheep. These eggs hatch into flesh-eating maggots.

Known as ‘fly strike,’ this disease is estimated to cost the Australian sheep farming industry $280 million.

Australia’s native scavengers are more effective than introduced species like foxes and cats in removing blowflies.

“Blowflies are a massive problem for the Australian sheep farming industry. They cause a horrible disease that is expensive for farmers to manage and a real animal welfare problem for sheep,” says Tom Jameson, a PhD researcher at the University of Cambridge in the UK and first author of the study published in the journal Ecology and Evolution.

It is the first study to show the importance of large reptiles as scavengers.

Jameson compared the scavenging activity of different animals by leaving hundreds of dead rats at feeding stations with camera traps.

By counting the number of blowfly maggots on the carcasses and looking at the camera traps to see which scavenger had feasted on the dead rats, Jameson was able to determine the behaviours of the different animals.

“After 5 days we’d find over 1000 maggots in one rat if a scavenger hadn’t found it,” Jameson says. “Those maggots produce blowflies that can spread up to 20km in a week, putting local sheep flocks at risk of fly strike.”

“The results suggest that conservation work in southern Australia to remove invasive species should also focus on boosting the population of heath goannas and other native species because they’re really important for the wider ecosystem,” Jameson adds.

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