In June 1935, roughly a hundred cane toads were brought from Hawaii to Gordonvale in Queensland and released to control the French's cane beetle and the greyback cane beetle. The plan overlooked basic natural history. Adult beetles spend much of their time on the upper parts of cane stalks, out of a ground-dwelling toad's reach, and the toad forages at night while the beetles are largely active by day.
The toads thrived on everything else. From that small founding release the Australian population now numbers in the many millions and has spread across Queensland and the Northern Territory into Western Australia, advancing at a front that has accelerated over time as longer-legged individuals reach the edge first.
The damage is chiefly poisoning rather than competition. Native predators including northern quolls, goannas and freshwater crocodiles have no evolved tolerance for the bufotoxins in the toad's parotoid glands and die after attempting to eat one. Population crashes have followed the invasion front, with some recovery where predators learn or evolve avoidance.