The Government of Western Australia has produced an extensive State Cane Toad plan that is currently open for comment. The invitation to comment is open until 25 June 2009.
Cane toads have only just entered Western Australia, almost three quarters of a century after introduction in north Queensland. It is expected that they will continue to move across the top end of the State and end up inhabiting most of the Kimberley region. The Pilbara region will probably stop their expansion south due to lack of water, but at least one study indicates a range that could take in Perth, Adelaide, Melbourne and Sydney.
As toads move through an area, they kill a lot of wildlife. Unaware predators eat them and die. Not all predators of course. Some like the keel back snake are resistant to toad poison, others learn and others evolve. The toads predate species themselves and again the impact varies. One study showed perhaps a "silver lining" to the toad plague through a reduction in mosquitoes but we know almost nothing about toad impact on narrow-range land snails (of which there are many species in the Kimberley) or on birds for example. Chris Boland of the ANU showed that toads will seek out the nests of Rainbow bee-eaters from up to a kilometre away and that they prefer hatchlings to eggs.
But most wildlife recovers and, to our current knowledge, none become extinct.
For many years, some wildlife managers have pointed out that Queensland did not lose species as the cane toad moved through the landscape. The fox is associated with probably over a dozen extinctions whereas no-one can convict the cane toad of a single extinction.
Over time, the ecosystem adjusts and species that were depleted return. But maybe that's because we don't know enough - no-one was studying snails and birds as toads moved across Queensland. We don't know enough about the rate of return of wildlife - some may take decades.
So the job of a State Cane Toad Plan is a really difficult one. Does it attempt to "Stop The Toad" from entering ecosystems? Or does it advocate "coping and recovery" as the toad does its damage and species recover? Obviously everyone would prefer stopping the toad altogether, but nothing to date has worked sufficiently well to rely on this approach. Relying on recovery has its risks as well, because we simply don't know enough to dismiss the impact of the toad on species like land snails and be confident they'll cope.
No doubt it will be impossible to develop a plan that will satisfy everyone. But the WA Government has asked for input from anyone that would like to comment. To access the draft plan, click here.