Halting invasive species along a sensitive corridor

Cane toads still remain as one of the greatest examples of invasive species in modern history.  With their rapid evolution, high dispersal ability and wide-spread established range, eradicating them from native habitat remains one of the biggest ecological challenges in Australia.  Currently, cane toads threaten to invade the ecologically sensitive Kimberley-Pilbara coastal corridor, which provides them crucial, non-arid habitat to cross from northern Australia into the western region of Australia.  Knowing that cane toads can establish satellite populations at “invasion hubs” at the forefront of an invasion, Tingley and colleagues set out to determine whether they could be stopped by limiting their colonization of a critical resource: artificial waterbodies, established in the name of pastoralism.  They used dispersal data of cane toads to ask the questions: can cane toads spread easily through the corridor given the spatial configuration of artificial waterbodies, and can cane toads be stopped easily if excluded from these waterbodies?

The answer seems to be a resounding yes in both cases.  In their simulations, cane toads were highly likely to colonize through the corridor in a mean time of 25 years using artificial waterbodies, but highly unlikely to do so if they had to rely only on natural waterbodies.  The authors also specifically identified three potential barrier points, which, if artificial waterbodies were removed, might have the greatest impact on limiting toads from traversing the corridor.  They suggest several management strategies, such as toad-proof fencing, manual removal, or switching from earthen dams to tanks, although they are practical about the enormity of counteracting such a strong invasive over such a large region of land, much of which is privately held.  The modelling framework used here could be applied to any organism that relies on a critical resource with patchy distribution.  Interestingly, the study highlights the fact that corridors can act as a beneficial bottleneck for invasive species by forcing the invasion through a pinch point.  The species can then be more easily controlled and slowed down.