Cues for cannibalism: cane toad tadpoles use chemical signals to locate and consume conspecific eggs

Although animals of many species kill and consume conspecifics, most such cases probably involve serendipitous encounters between the individuals concerned. In some taxa, however, cannibalism is an active process, with predatory individuals searching out and consuming specific types of conspecific prey items. Although anuran tadpoles often have been reported to consume conspecific eggs, this behaviour has been interpreted as a by-product of usual foraging behaviours rather than a result of targeted searching. Our field and laboratory studies in tropical Australia show that the tadpoles of invasive cane toads Bufo marinus are strongly attracted to chemical cues from conspecific eggs; the effective cues are released late in embryonic development, as the jelly coat breaks down. Tadpoles of native Australian frog species were attracted to the eggs of toads only rarely. If deployed as bait in traps, chemical cues from toad eggs could provide a way to selectively remove toad larvae from waterbodies.