Restricting access to invasion hubs enables sustained control of an invasive vertebrate

© 2015 The Authors. Biological invasions often occur through expansion of satellite populations that become established at 'invasion hubs'. Invasion hubs can result from random dispersal events, but frequently arise when invading individuals actively choose habitats using cues that signify high-quality environments where the fitness consequences are positive. Theoretical studies suggest that targeted control at invasion hubs can effectively suppress the populations and impacts of invaders. In arid Australia, small dams that provide water for livestock function as invasion hubs by providing an invasive vertebrate, the cane toad Rhinella marina, with refuge from extreme aridity during the annual dry season. Toads are attracted to dams and use them as stepping stone habitats from which they disperse during rainy periods. Here, we ask whether sustained control of this invasive vertebrate can be achieved by converting invasion hubs into ecological traps. We did this by manipulating invasion hub habitats to induce a mismatch between toads' habitat preference and the fitness consequences of their habitat choice to cause high mortality. We constructed fences to exclude toads from dams and maintained these fences for 1 year. This period encompassed periods of dry and wet seasonal climatic conditions. Our manipulation did not alter the attractive cues for invading toads which died en masse while attempting to settle at fenced dams that prevented toads from reaching water. Toad populations at the fenced dams were suppressed by 1-2 orders of magnitude compared to unfenced controls and procedural controls. Toad populations remained suppressed for a year after exclusion. By excluding toads from dams, we converted invasion hubs into ecological traps and effectively thwarted the reinvasion of cane toads. Our research suggests that water exclusion devices could be used to prevent toad invasion or to control cane toad populations in arid landscapes colonized by toads. Synthesis and applications. Our study demonstrates that sustained control of invader populations can be achieved by restricting their access to invasion hubs. Control of invasive species via elimination of invasion hubs could be conducted reactively, to control established populations of invaders, or conducted strategically, by rendering invasion hubs unsuitable for colonization ahead of the invasion front to prevent further population spread