Feeding chemical-laced cane toad corpses to freshwater crocodiles in Western Australia’s north has prevented a “mass mortality event”, according to the results of a new study conducted in the state’s Kimberley region.
The invasive species has made its way across northern Australia, destroying predator species such as freshwater crocodiles and goannas, impacting various ecosystems.
Recent data in WA shows the cane toad front is expected to reach Broome as soon as 2026.
The study, run by Macquarie University, Bunuba Rangers and the Department of Biodiversity, Conservation and Attractions (DBCA) between 2019 and 2022, baited four gorge systems — Windjana Gorge, Bandilngan, Danggu Geikie Gorge and Scrootens waterholes.
Researchers deployed more than 2,000 baits across the Fitzroy Valley, consisting of toad carcasses with their toxin removed and a nausea-inducing chemical inside. Lead researcher Georgia Ward-Fear said the study was the first time researchers had been able to show that crocodiles could learn taste aversion.
“Across northern Australia, we’ve seen huge declines of some populations of freshwater crocodiles of up to 70 per cent, and this is a huge blow to the ecosystem,” Dr Ward-Fear said.
“We’ve stopped crocodile deaths in an area that was experiencing high rates of death and we’ve also prevented deaths entirely in an area where we are expecting high rates of death, so that’s really exciting.”
Dr Ward-Fear said once the cane toad invasion had arrived in the Fitzroy Valley, researchers saw no mortalities in the areas they had baited.
“We compared this to an area where we had not done the baiting that was invaded at the same time and we saw high rates of crocodile mortality,” she said. Dr Ward-Fear said the results of the study could be applied to a range of issues that had significance globally.
“In Madagascar, there is another toad invasion with a similar species that’s closely related to the cane toad and just as poisonous,” she said.
“We’re hoping the results of our research can be directly applied to that system, as well as other toad or toxic species invasions worldwide.”
Crocodiles are quick learners
DBCA invasive species project officer Sara McAllister said it was significant to observe how quickly the reptiles had learnt to avoid cane toads.
