Three-quarters of a century after the invasive and toxic cane toad arrived in Australia scientists are still battling to control its impact. Introduced to control another pest, a beetle, the toads have become an invasive ecosystemic disaster
The cat-sized quoll was once widespread in northern Australia. These marsupials have a dappled coat and bushy tail and females have a pouch that opens when they are rearing young.
They also have a fatal attraction for the cane toad. If a quoll catches and consumes a cane toad it also ingests a fatal dose of toxin. There is no learning curve, one encounter one mistake, is fatal. As a result, the number of quoll has plummeted as the range and numbers of cane toads have grown.
Scientists in Sydney are working on introducing a learning curve into the experience for quolls. They "fed quolls small toads laced with the poison thiabendazole. The dose was not enough to be harmful, but the sickness the quolls experienced was enough to put them off eating the toads again", according to timesonline.co.uk.
The study, led by Professor Rick Shine, tested whether northern quolls could be taught to avoid eating cane toads through a process called conditioned taste aversion. In layman's terms Rick says "Taste aversion can be incredibly long-lasting. I drank too much scotch when I was 18; I'm 60 now and haven't touched it since." And it seems to affect quolls the same way.
On the basis of this research there are plans to aerially seed critical areas of habitat so the quolls have the opportunity to learn to avoid the toxic toads.
In another vein, the indigenous meat ant has been observed eating young toads with no ill effects and has been investigated as a biological control.
Cane Toad Bufo marinus, Springbrook National Park, QLD Australia.