Pest control by the public: Impact of hand-collecting on the abundance and demography of cane toads (Rhinella marina) at their southern invasion front in Australia

Abstract

The population dynamics of an alien species can be heterogeneous across a geographically widespread invasion– and thus, the effectiveness of alternative control methods can vary. Research in tropical Australia has concluded that hand-collecting adult cane toads (Rhinella marina) is unlikely to offer a useful means of control, because the offtake rates needed to significantly reduce toad abundance are not achievable. Our data from southern (temperate-zone) Australia are more encouraging. We captured, marked and released toads in sites soon to be “toad-busted” by volunteer groups, and compared the animals that were collected to those known to be present. The volunteers disproportionately collected adult rather than subadult toads, probably because larger animals are easier to find. A single night’s “toad-busting” by volunteers removed 28%–47% of local toads. If conducted several times a year, and combined with recently-developed methods to curtail recruitment (pheromone-based trapping of larvae), that offtake could massively reduce toad abundance and perhaps, eradicate isolated populations at the southern margins of the cane toad invasion.