Invasive species can wreak havoc on native ecosystems. Sometimes, they can be their own worst enemies, too. In Australia, the cane toad (Rhinella marina) was brought in to keep down pests until it became a nuisance itself. Even in a country with as many poisonous species as Australia, the cane toad, a native of South America, secretes a poison that keeps away just about all predators. But that doesn’t mean nothing eats it. The cane toad has become a cannibal.
In a study published in the Proceedings of the National Academies of Science, researchers have documented cane toad tadpoles feeding on one another. “This cannibalism seems to be an evolutionary response to the lack of competing species in its invasive range, causing cane toads to turn on their remaining competition: each other,” writes Ars Technica.
In response, tadpoles have begun rushing through their hatchling stage to avoid being gobbled up by others—“an evolutionary arms race,” researchers wrote, “between the cannibalistic tadpole stage and the vulnerable egg and hatchling stages in invaded habitats.