By Phil Mercer
BBC News, Sydney
Authorities in northern Australia have launched a competition to find the most successful way of slowing the devastating spread of cane toads.
Cane toads have overwhelmed the local wildlife in Queensland
The poisonous amphibians have become one of the country's most dangerous pests and are advancing up to 50km (31 miles) every year.
They were introduced in Australia from Hawaii in the mid-1930s to combat the spread of cane beetles.
There could be as many as 100 million cane toads in Australia today.
The experiment is widely considered to have been a complete disaster.
Even freshwater crocodiles and dingos are no match for cane toads.
Other native fauna, including tiger snakes and kangaroos, have died after eating their poisonous skins.
In Australia's tropical north, the authorities are so desperate to stop the cane toads that they are offering a reward for the most effective way to arrest their relentless advance.
Inventor Andrew Arthur believes his toad blaster - a battery-powered loudspeaker system which imitates the sound of a toad - is the answer to this environmental crisis.
"I'd see it working most effective on the frontline where the toads are crossing rigs lines, looking for places to breed," Mr Arthur says.
"This call comes out, the toads would think... oh, this toad has got a great place to breed, let's go there," he added.
As they moved towards the designated area, the toads could then be trapped, he said.