Georgia Ward-Fear of the University of Sydney (Australia) and her colleagues have found that Cane Toads (bufo marinus) are in fact quite vulnerable to a native species of Australian ant. Although cane toads are poisonous to most of their predators, these ants are immune to the toxins secreted by the amphibians.
To measure the toad’s response to attack, they placed toads in a shallow plastic dish and tapped on it until it had completed five hops. They also measured the toads’ activity in the wild vs. the ants’ activity.
They concluded that because the toads have shorter, slower hops than other native frog species and share similar activity patterns with the ants, they are far more vulnerable to meat ant attack. As toads mature, they are active diurnally, which increases their encounters with meat ants. The experiment also showed that many toads failed to detect and evade approaching ants.
Functional Ecology Vol 23, Pages 559-568 (2009)