Nobody likes to get food poisoning. At best, there are uncomfortable symptoms like stomach pain, diarrhea, nausea, and more. At worst, lifelong injury or even death are possible. However, can food poisoning sometimes lead to a positive outcome?
Testing that theory, Australian researchers have developed an innovative method to protect freshwater crocodiles from the deadly effects of invasive cane toads. The study, published recently in Proceedings of the Royal Society B, demonstrates a successful intervention that reduced crocodile mortality rates by up to 95% in some areas.
Cane toads were introduced to Australia in 1935 to control beetles damaging sugarcane crops. However, this plan backfired as the toads spread across the continent, unintentionally killing numbers of other animals. Now numbering an estimated 200 million, these amphibians produce potent toxins that are lethal to many native species, including freshwater crocodiles.
The impact on crocodile populations has been severe, with some areas experiencing up to 70% population decline. This loss is particularly concerning as crocodiles play a crucial role in their ecosystems as top predators. Their decline can lead to downstream effects throughout the food web, including increases in mid-level predators and negative impacts on bird nesting.
A team at Sydney’s Macquarie University developed a taste aversion strategy to address this problem. They created bait using the lower halves of cane toad carcasses, which contain less toxin, and injected them with a compound that induces nausea in crocodiles, effectively giving them food poisoning. This method aims to teach the reptiles to associate cane toads with temporary illness, discouraging them from consuming lethal doses in the future.
The researchers deployed this bait in canoes, hanging it from stakes at the water’s edge in areas where crocodiles and cane toads congregate during the dry season. Control chicken carcasses were also used to compare results.
The intervention proved highly effective, particularly in Danggu Geikie Gorge National Park, where cane toads had arrived two years prior. In this location, crocodile mortality rates decreased by 95%, while untreated control areas continued to experience high death rates.
This approach falls under the growing field of conservation behavior, which focuses on managing coexistence between native and invasive species through behavioral interventions. Such methods are often faster-acting, easier to implement, and more ethical than culling invasive species.
While some experts suggest that repeated training may be necessary to maintain the effect, the study’s authors observed sustained low mortality rates throughout the two-year study period. They also note that as adult cane toads breed in new areas, their less toxic offspring may provide a safer learning opportunity for crocodiles.
The success of this intervention has led to its deployment by Indigenous rangers and wildlife management agencies across northern Australia. As an interim solution, it offers hope for preserving crocodile populations and maintaining ecological balance in affected areas while longer-term strategies to control cane toad populations are developed.
Commenting on this story, one national food poisoning lawyer said, “Too often, food poisoning in humans is accidental and not intentional. However, a bout of bad food poisoning may keep one from eating that food again for a long time, just like with these crocodiles!”
