Eat something that's bad for you and you get sick, effectively teaching you to never eat that thing again. But if you eat something that kills you, there's not much room left for learning, is there?

That's the problem in Australia, where the endangered northern quoll (Dasyurus hallucatus), a small, cat-sized marsupial, has been driven to near-extinction by eating poisonous cane toads (Bufo marinus). Now some scientists are trying to help quolls, and maybe other species, by teaching them that cane toads are not food and should be avoided.

What's that? Teach an endangered species not to eat the very thing that kills it and made it endangered? It's so crazy it just might work!

You've probably heard all about cane toads before: they were introduced to Australia to combat cane beetles, but they proved so poisonous to the native fauna that the toads quickly overran almost the entire continent and have since killed off millions of snakes, lizards, mammals and even crocodiles.

Rick Shine, Stephanie O'Donnell and Jonathan Webb from the University of Sydney had the idea to try to teach quolls that cane toads were bad for them. They took 62 young quolls and fed half of them with small dead cane toads which were laced with nausea-inducing thiabendazole. The cane toads were small enough and the toxic dose not large enough to kill the toad-fed quolls, but it did make them sick.

The next step was to introduce a live cane toad to the quolls to see if they attacked it. They did not. All 62 quolls were then fitted with radio collars and released into the wild. The 31 who had been introduced to cane toads "survived up to five times longer than 'toad-naïve' quolls," Shine and his colleagues wrote in the April 13 issue of the Journal of Applied Ecology.

"Our results show that this kind of approach works. If you can teach a predator that cane toads make you sick, then that predator will leave them alone afterwards. As a result, animals like quolls can survive in the wild even in a toad-infested landscape," Webb said in a prepared statement.

Their work isn't done. The researchers still need to figure out how long this "conditioned taste aversion" to cane toads will last, or if the quolls will revert to cane consumption. They would also like to see if other species such as goannas and bluetongue lizards could be taught not to eat cane toads.

Photo: Northern quoll, courtesy of Jonathan Webb