The accelerating invasion: dispersal rates of cane toads at an invasion front compared to an already-colonized location
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Evolutionary theory predicts that individuals at an expanding range edge will disperse faster than conspecifics in long-colonized locations, but direct evidence is rare. Previous reports of high rates of dispersal of cane toads (Rhinella marina) at the invasion front have been based on studies at a single site in the Northern Territory. To replicate the earlier work, we radio-tracked free-ranging toads in the Kimberley region of northwestern Australia (at the westward-spreading invasion front) and 500 km northeast, on the Adelaide River floodplain of the Northern Territory (where toads had already been present for 6 years). For comparison, we also radio-tracked native frogs (Litoria caerulea and L. splendida) at the same sites. Consistent with the earlier reports, invasion-front cane toads travelled further per day, were more highly directional, and re-used refuge sites less frequently, than did conspecifics from an already-colonized site. In contrast, native frogs showed similar movement patterns in the two study areas. Our results confirm previous reports, and suggest that accelerated dispersal may be a common feature of individuals at the vanguard of a biological invasion.
KeywordsBufo marinus Replication Spatial ecology Tropical Australia
We thank Bill Stewart, Corrin Everitt, Samantha Price-Rees, Ruchira Somaweera, Jai Thomas, Charlie Sharpe, Samantha Maindok, Greg Smith, David Williams, and Narelle Brook for logistical support in Western Australia, and Michael Crossland in the Northern Territory. All procedures were approved by the University of Sydney Animal Ethics Committee (Protocol L04/5-2010/2/5334) and conducted under permits from Northern Territory and Western Australia Parks and Wildlife (39857 and SF007610, respectively).
This study was funded by the Australian Research Council (DP0984888, FL120100074), and the Brazilian Conselho Nacional de Pesquisa (CNPq - fellowship to Camila Both).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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