In 2010, Australian scientists fed native predators toad sausages spiked with a nausea drug so they would learn to avoid deadly cane toads: a trick now used to train quolls before toads arrive

If you’ve ever gotten sick after eating a particular food and avoided it for years, you might understand the scientific reasoning behind a bizarre conservation experiment in Australia. A 2010 study published in the Journal of Applied Ecology showed that baby quolls that ate a nausea-inducing toad snack were much more likely to survive in the wild. It seemed almost too simple, but the data backed it up, and more than a decade later, wildlife managers are still expanding on the idea.

Meet the quoll, and the toad that's wiping it out
The northern quoll is a small, cat-sized spotted marsupial that was once found throughout northern Australia. Then the cane toad arrived. According to the study, ‘Conditioned taste aversion enhances the survival of an endangered predator imperiled by a toxic invader,’ the cane toad was introduced to Queensland in 1935 to control beetles on sugarcane farms and has since spread around the continent. Most native Australian predators have never encountered cane toad toxin, and so have no built-in caution around cane toads. A quoll comes across a toad, eats it like any other prey, bites down, and often dies within hours. The study found that quoll populations went locally extinct across large areas of northern Australia after cane toads invaded, and the species was later listed as endangered under Australian law.

Teaching an animal to say "no thanks" to poison
The University of Sydney researchers borrowed an idea already familiar to psychology: conditioned taste aversion. It’s the same reflex that kicks in after someone has one bad bout of food poisoning and refuses to eat that food again, even if the food wasn’t the real culprit. Animals developed this response for a good reason: it helps them learn quickly which foods to avoid, without having to go through repeated near-death experiences.


To test it out, the team split young captive-raised quolls, who were to be released into the wild, into two groups. One of the groups, called “toad-smart,” was given a small dead toad that contained a chemical known to cause nausea, thiabendazole, between one and seven days before release, the study noted. The quolls got sick, got better, and left with a distaste for the taste and smell. The other group, the “toad-naïve” ones, never learned that lesson. Then both groups were shown a live toad they could see and smell but not eat, to gauge who wanted to attack it and who backed off.

The results were hard to argue with
Once released into a toad-infested habitat and tracked by a radio collar, the difference showed up fast. The study noted that five of 17 untrained male quolls died within days of release, killed as soon as they attacked large cane toads. Estimated daily survival rates were higher for trained quolls of both sexes; 0.94 for females and 0.84 for untrained females, and 0.88 for males and 0.58 for untrained males. Untrained males fared the worst, mainly because male quolls tended to be bolder around new animals and less likely to give a toad a tentative sniff before biting it. Females from both groups performed better, were more cautious in their approach, and hence more likely to learn from an encounter than die from one.

From lab experiment to real-world conservation tool
What makes this story worth revisiting isn’t the original experiment from 2010, but what followed. Outside the enclosure, in the Australian bush, wildlife biologists applied the same principle. The 2018 study, ‘Not such silly sausages: Evidence suggests northern quolls exhibit aversion to toads after training with toad sausages,’ in the journal Austral Ecology reported that researchers made a “toad sausage” out of minced cane toad meat laced with the same nausea-inducing chemical, to be left out for wild quolls to find on their own, with no capture required. Field trials conducted in the Kimberley region of Western Australia found that the most common species attracted to these baits were wild quolls, with about 40 to 68 percent of quolls that took a bait subsequently avoiding eating more.

Researchers followed up with a landscape-scale study published in the journal Wildlife Research to see if they could drop these sausage baits across whole quoll populations before the cane toads arrived, essentially pre-training local wildlife before the invasion.

Why this matters beyond one small marsupial

To American readers, this may seem like a niche story about an unfamiliar Australian animal. But in fact, it’s a case study for a larger concept: when it’s impossible to get an invasive species out, scientists can try to change the way native animals respond to it. Conditioned taste aversion has also been used in the US to prevent coyotes from preying on sheep and crows from raiding endangered birds’ nests, well before this quoll research began.

The northern quoll is still fighting on. Cane toads continue to spread, and taste aversion training is not a perfect fix. Two trained male quolls still attacked large toads after release, according to the original study, and researchers are still refining doses and bait design. But the core finding holds: one carefully engineered bad meal can mean the difference between a species surviving an invasion and disappearing altogether.