Scientists from Macquarie University, working alongside Bunuba Indigenous rangers and the Department of Biodiversity, Conservation and Attractions (DBCA) in Western Australia, have come up with a new way to protect freshwater crocodiles from the dangerous, invasive cane toads spreading across northern Australia.
This approach could save the lives of these culturally and ecologically important animals.
Freshwater crocodiles, known scientifically as Crocodylus johnstoni, hold a special place in the traditions of the region’s Indigenous people and play a crucial role in maintaining the balance of local ecosystems.
However, the spread of cane toads, which were introduced to Australia from South America in the 1930s, has led to the deaths of many native animals, including freshwater crocodiles.
These crocodiles have no natural defense against the poisonous toads, making them particularly vulnerable.
The research, led by Dr. Georgia Ward-Fear from Macquarie University and published in Proceedings of the Royal Society B, tested a technique called conditioned taste aversion (CTA) to teach crocodiles to avoid eating cane toads.
The idea is simple: if the crocodiles associate eating a cane toad with feeling sick, they’ll learn to avoid the toads in the future.
From 2019 to 2022, Dr. Ward-Fear and Professor Rick Shine, along with local rangers and DBCA staff, set up bait stations across four large gorge systems in the Kimberley region of north-western Australia.
They used cane toad carcasses that had been treated with a nausea-inducing chemical, making the crocodiles feel sick but not harming them. As a control, they also used chicken meat that didn’t cause nausea, to see how effective the training was.
Bunuba ranger coordinator Paul Bin Busu and his team noticed that at first, the crocodiles would eat the cane toads, but after getting sick, they began to avoid them. By the end of the trial, the crocodiles were mostly eating the chicken baits and leaving the cane toads alone.
The results were impressive. In areas where the baiting took place, crocodile deaths dropped by 95%, and in some cases, there were no deaths at all. The technique proved effective not only as the toads first arrived but also in areas where the toads had been established for a few years.
This success shows that collaboration between scientists, Indigenous rangers, and land management agencies can be a powerful tool for conservation. By teaching crocodiles to avoid eating cane toads, the project is helping to protect these important animals and restore balance to the local ecosystems.
The team hopes to apply this technique to other species and areas affected by invasive predators. As Professor Rick Shine noted, in a world where invasive species are spreading rapidly, innovative approaches like this one can help protect vulnerable ecosystems and the wildlife that depends on them.
