Sugar crop yield vs cane toads

In 1935, cane toads (Rhinella marina) were brought to Australia to control insect pests. The devastating ecological impacts of that introduction have attracted extensive research, but the toads’ impact on their original targets has never been evaluated. Our analyses confirm that sugar production did not increase significantly after the anurans were released, possibly because toads reduced rates of predation on beetle pests by consuming some of the native predators of those beetles (ants), fatally poisoning others (varanid lizards) and increasing abundances of crop-eating rodents (that can consume toads without ill-effect). In short, any direct benefit of toads on agricultural production (via consumption of insect pests) likely was outweighed by negative effects that were mediated via the toads’ impacts on other taxa. Like the toad’s impacts on native wildlife, indirect ecological effects of the invader may have outweighed direct effects of toads on crop production.