Australia Imported Cane Toads to Solve a Pest Problem and Created a Bigger One

The cane toad introduction is one of ecological history most cautionary tales. Queensland farmers were suffering heavy losses from the native cane beetle, and the cane toad had proven effective against similar pests in Hawaii. What nobody adequately accounted for was that the cane beetle larvae live underground, while the cane toads hunt on the surface and never reached them. What the toads did find was an entire continent of naive native predators with no evolutionary experience of their potent bufadienolide toxins. Species such as the northern quoll, freshwater crocodiles, goannas, and multiple snake species have experienced severe population crashes after eating cane toads. The toads breed prodigiously, with each female capable of laying up to 35,000 eggs twice a year, and they have spread across more than 1.2 million square kilometres. Decades of attempts to control them using traps, targeted gene drives, and biological agents have met with limited success. The original 102 toads are now estimated to have spawned a population exceeding 1.5 billion.