Crocodiles are one of the native predators in Australia threatened by the spread of poisonous cane toads. These lethal toads have been responsible for killing hungry crocs across the country. However, researchers have discovered that a good scare can make these predators picky eaters when it comes to toads.
Researchers at Macquarie University in Sydney, led by conservation scientist Georgia Ward-Fear, have been studying the effects of exposing freshwater crocodiles to the taste of nasty cane toads. By feeding the crocs lithium chloride-laced carcasses of invasive cane toads, the researchers found that the crocodiles were far less likely to eat live toads when they encountered them in the wild. This conditioning technique could potentially help prevent the die-offs that occur as cane toads continue to invade new territories in Australia.
Cane toads were introduced to Australia in the 1930s and have since become a major threat to native species. Their toxic glands make them deadly to predators that attempt to eat them. As the cane toads spread across the continent, freshwater crocodiles have been falling victim to these poisonous amphibians. In 2008, researchers observed a significant decline in crocodile population densities along the Victoria River following the invasion of cane toads.
The idea behind the study was to teach the crocodiles to avoid cane toads before they encountered them in the wild. In previous experiments with other native predators, such as large monitor lizards, researchers found success in using conditioned taste aversion to train the animals to avoid eating toxic toads. However, crocodiles pose a unique challenge as they typically ambush and consume their prey whole, making it difficult to administer small doses of toxic toads for training.
To train the crocodiles, the researchers worked with the Bunuba Rangers, an Australian Indigenous group that views freshwater crocodiles as an important part of their cultural heritage. The team collected dead toads, removed the toxic glands and internal organs, and laced the remaining toad meat with lithium chloride. They then placed these baited toads near the water’s edge in several gorges in the central Kimberley region of Australia, alongside motion capture cameras to monitor the crocodiles’ behavior.
After the live toads arrived in the area, the researchers observed the crocodiles to see if they had learned to avoid eating them. By examining the carcasses of dead crocodiles, the team found that those crocs that had been exposed to the conditioned taste aversion training were far less likely to die from consuming live cane toads. In some areas where the training had been conducted, the mortality rate among crocodiles that ate live toads dropped significantly compared to control areas where no training had taken place.
The success of the study has been hailed as an innovative and effective conservation tool by experts in the field. Colleen St. Clair, a conservation biologist at the University of Alberta, praised the use of conditioned taste aversion as a method for protecting wildlife from toxic invaders. The results of the study show that even ancient techniques, such as using lithium chloride to induce vomiting, can be effective in training animals like crocodiles to avoid dangerous prey.
The implications of this study go beyond just protecting crocodiles from cane toad poisoning. It also highlights the importance of collaboration between researchers, Indigenous communities, and conservationists in developing effective strategies for wildlife conservation. By combining traditional knowledge with scientific research, the team was able to achieve a significant reduction in crocodile mortality due to cane toad consumption.
Overall, the study serves as a reminder of the complex relationships between predator and prey in natural ecosystems. By understanding the behavior of both predators and prey, researchers can develop innovative solutions to address conservation challenges and protect vulnerable species from extinction. The success of the conditioned taste aversion training in crocodiles offers hope for the future of wildlife conservation in Australia and beyond.