New research, published on Wednesday in Proceedings of Royal Society B, says the country's fast-growing cane toad population – believed to exceed 200 million – could be controlled by deploying its own highly toxic poison, which attracts its own tadpoles but repels native tadpoles, fish and insects.
A team of scientists says the toxins, secreted from the shoulder glands of dead toads, could be used to lure the tadpoles into traps en masse before they spread to the wild. A single clutch laid by a cane toad can contain more than 30,000 eggs – three times as many as native frogs.
"This is the first powerful tool we have created to control cane toads," said the lead author, Rick Shine, a professor at Sydney University .
"Even if you catch and kill 99 per cent of the adult toads in an area, the few that are left can produce so many offspring that before you know it you are back to where you started ... If we can do this, then removing adult toads can make a big difference because there are no new toads being born to replace the ones we are eliminating."
Cane toads have spread exponentially across the northern half of Australia since being brought over in 1935 from Hawaii by the Bureau of Sugar Experiment Stations as a way to control cane beetles in Queensland. The cane toads, it turned out, did not eat the beetles but they have since spread across Queensland, the Northern Territory, New South Wales and Western Australia.
Predators that try to kill them such as crocodiles, goannas and quolls have been killed by the cane toad's poison.
"We go to great lengths to protect the environment from human impact and then the toads come through and knock out thousands of varieties of native wildlife," said Robert Capon, a professor at the University of Queensland.
"The impact on the environment has been disastrous."
An Adelaide University scientist, Ian Musgrove, said that after cane toad tadpoles hatch they hunt down other cane toad eggs to preserve a food supply and to ensure that not all of the tens of thousands of eggs hatch.
"The cane toad tadpoles are cannibals," he told The Conversation (http://theconversation.edu.au/great-invaders-poison-could-also-be-its-downfall-7609).
"It pays the early hatching tadpoles to hunt down and eat the cane toad eggs that have not yet hatched. Of course, cane toad eggs are resistant to the toxins that they secrete, so the toxin is not a deterrent to them."