The impact of lungworm parasites on rates of dispersal of their anuran host, the invasive cane toad

Translocation of native-range parasites to control invasive species is effective only if the parasite substantially impairs either the viability or dispersal rate of the invasive host. Lungworms (Rhabdias pseudosphaerocephala) of cane toads (Rhinella marina) were introduced to Australia from the toad's native range, along with the toads, and have been suggested as a potential biocontrol of invasive toads due to various negative impacts on toad viability. We conducted two radio-telemetry studies on a tropical floodplain to specifically assess the parasite's impact on toad dispersal. First, a retrospective correlative analysis of data from field-collected animals showed that toads infected with lungworms moved farther, not less, than uninfected conspecifics. Second, an experimental study (comparing movements of experimentally infected toads vs. uninfected controls) showed that lungworms did not modify rates of toad dispersal. In addition, experimental infection with lungworms did not elicit an immune response substantial enough to influence dispersal behaviour. Thus, we conclude that increasing lungworm densities at the invasion front as an attempt at biocontrol would not slow down the spread of cane toads.