Researchers train goannas not to eat cane toads in WA Kimberley region

Researchers have trained goannas not to eat cane toads. (Supplied: Miles Bruny/Georgia Ward-Fear/WWF Australia)

Researchers have trained goannas not to eat cane toads in a bid to mitigate the toxic pest’s impact on native fauna.

The study, published in the Society for Conservation Biology’s journal Conservation Letters, found the technique had a significant impact on maintaining population numbers.

Working alongside Bunuba Rangers and wildlife management agencies, researchers introduced yellow-spotted monitors – a type of goanna – to small doses of the cane toad toxin, ahead of the “cane toad frontline” in Western Australia’s Kimberley region.

Lead researcher Georgia Ward-Fear said the goannas developed what was known as “conditioned taste aversion”.

“We actually give goannas small doses of cane toad toxin that makes them sick but doesn’t kill them and then they can learn from that experience,” she said.

Dr Ward-Fear said large, toxic adult cane toads tended to be at the forefront of the areas they were invading and that they killed any animal they interacted with.

“What we do is we bring baby cane toads from behind the frontline to just ahead of the frontline so that animals have a potential learning experience with a small cane toad,” she said.

[MAP: Fitzroy Valley]

Teacher toads

The idea of using “teacher toads” has already been tested on a smaller scale, but this study demonstrated the method could be used at an ecosystem level.

For three years, researchers surveyed goanna populations at sites across the Fitzroy Valley before and after the arrival of cane toads, which were first sighted in the area in March 2019.

As little as six per cent of the goanna population remained after the arrival of cane toads at control sites where the technique was not used.

But in areas where teacher toads were introduced at least 35 per cent of the goanna population remained.

“The strategy has been so successful,” Dr Ward-Fear said.

“We are applying it to other studies and other species with the hope of increasing their survival and trying to decrease the impact of cane toads, because they’re here to stay, unfortunately.”

Broad benefits

Teacher toads have also proved successful with smaller marsupials and reptiles, but preserving apex predators such as goannas benefits the entire ecosystem.

Dr Ward-Fear said the absence of goannas would have a significant impact on other species.

“It is a very real possibility that the ecosystem will become unbalanced, because these animals sit at the top of the food web, keep the predators below them in check to stop them breeding up in high numbers and eating the animals below them,” she said.

“Ecosystems are such a delicate balance that once you take out a component, it has really big impacts for the rest of the ecosystem.

“Not to mention that they’re very important for Indigenous traditional owners all across northern Australia, because they’re important totemic species and important bush tucker.”