Inadvertent consequences of community-based efforts to control invasive species

Attempts to manipulate species abundances can have unforeseen consequences. Our studies suggest that community-group efforts to cull cane toads (Rhinella marina) invading Australia may interfere with the toad's local enemies. Abundance of the toad parasite Rhabdias pseudosphaerocephala and the ant Iridomyrmex reburrus (a toad predator) may decrease when community groups spray antiseptic (Dettol) at pond edges to kill toads. Our trials show that Dettol kills parasitic larvae and repels predatory ants; thus, community-group control efforts may reduce natural toad regulation. Conversely, volunteer "toad-busters" traversing isolated localities to collect toads may spread parasitic larvae via muddy footwear. Our trials show that larvae can remain alive in muddy boot-treads for at least a week, and our field data reveal changed parasite dynamics in areas where community groups are most active. Thus, the impacts of culling activities on this invasive species may be exacerbated or undermined by inadvertent interference with host-parasite and predator-prey interactions.