An evaluation of methods used to cull invasive cane toads in tropical Australia
To identify cost-effective ways to control invasive species, we need to evaluate alternative methods. The invasion of tropical Australia by cane toads (Rhinella marina) has killed many native predators, prompting efforts to cull adult toads. We analyzed a dataset on > 17,500 toads killed by government-employed teams from 2005 to 2008, using a range of methods (incidental captures, targeted searches, traps) as well as records of toads found as road kills. The culling occurred in the northwestern part of the Northern Territory, moving west as the toad front expanded into Western Australia. Both season and method affected rates of capture and demographic attributes (sex ratio, proportion of adults) of the culled anurans, with a strong interaction between these factors. Most methods were more effective during and after the seasonal monsoons (when moist conditions facilitated anuran activity), but that seasonal variation was greater for numbers of toads found on the roads than captured in other ways. Juvenile toads and adult female toads constituted higher proportions of total captures in the Early Dry than in other times of year, reflecting seasonal breeding. Traps caught a higher proportion of adult female toads than did other methods, but overall had low capture rates. Rates of range expansion by toads were similar before, during and after the culling effort, suggesting that removing adult toads did not affect the speed of the invasion. Nonetheless, culling adult cane toads may be effective in some situations (“island” populations, extralimital translocations), and results from this program may be valuable for future toad-control efforts.
KeywordsAlien species Australia Biological invasion Bufo marinus Control methods Expansion rate Wet–dry tropics
We thank the people who contributed to the State Cane Toad Program over the years (Errol Kruger, Craig Mills, Sandra Fleischer, Jai Latham, Karin Carnes, Len Terry, Paul Sharp, Jesse Graham, and Jen Francis). We thank Rob Doria for producing the map. Manuscript preparation was supported by the Australian Research Council.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no conflict of interest.
This article does not contain any studies with animals (vertebrate) performed by any of the authors.
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