Invader control: factors influencing the attraction of cane toad (Rhinella marina) larvae to adult parotoid exudate

As invasive cane toads (Rhinella marina) spread across Australia, we urgently need effective ways to reduce the impact of toads on native fauna. One potential approach is to target the chemical cues (pheromones) used by the pest species for communication. In particular, the ‘attraction cue’ relies on the strong cannibalistic response of toad tadpoles towards conspecific eggs and hatchlings. Chemicals released into the water by developing embryos can be mimicked using exudate from the parotoid (shoulder) glands of adult cane toads, and this toxin can be used to lure cane toad tadpoles into a trap without attracting native aquatic species. This method works well under controlled conditions in the laboratory, but we know very little about factors that influence the success of tadpole trapping in the field. Our extensive trapping trials showed strong responses to the attraction cue under a wide range of conditions, but with reduced trapping rates at low water temperature (particularly in Western Australian populations), for early-stage tadpoles, and if the bait is frozen prior to use. Efforts to control cane toads using toxin-baited traps should consider these factors when applying trapping protocols in the field.