The Cane Toad in Australia

In 1935, about one hundred cane toads were brought from Hawaii to Queensland, in northeastern Australia. Sugarcane farmers hoped the large toads would eat the beetles that were damaging their crops. The plan failed almost completely. The adult beetles lived high on the stalks of the sugarcane, out of reach of the toads, which are poor climbers. Instead, the toads began eating almost anything else they could find.

With plenty of food and few natural enemies, the toads multiplied quickly. Today they occupy a large part of northern Australia, and their population is estimated in the hundreds of millions. Their spread has been especially harmful to native predators. Cane toads carry a powerful poison, and animals such as snakes, lizards, and small marsupials called quolls often die after a single attempt to eat one.

The toads have also changed as they spread. Researchers found that toads at the front of the invasion had longer legs than those in older populations and could travel farther each night. Meanwhile, some scientists are trying to protect native animals by teaching them to avoid toads — for example, by feeding quolls small pieces of toad meat that make them sick but do not kill them.