Reducing the impact of a toxic invader by inducing taste aversion in an imperilled native reptile predator

It is virtually impossible to eradicate invasive organisms once they have spread widely, and even low densities of invaders may have devastating impacts. We need to explore alternative management options that accept the inevitability of encounters between alien and native taxa, but reduce the negative consequences of those encounters. Conditioned taste aversion (CTA) is one approach that offers promise in this respect. The spread of the invasive cane toad Rhinella marina across northern Australia is devastating populations of predators such as the blue-tongued skink Tiliqua scincoides intermedia. Predators unable to tolerate the toads' powerful bufadienolide chemical defences are likely to die if they ingest a toad. We trained field-caught skinks to avoid eating cane toad flesh, by offering them toad sausages laced with a nausea-inducing chemical (lithium chloride). These individuals (and controls) were then released and radio-tracked as toads arrived at our study site in north-western Australia. Skinks that regurgitated after consuming the toad sausage survived after release, whereas most untrained animals were fatally poisoned by toad ingestion. Even if we cannot eradicate invasive cane toads, we can ameliorate their ecological impact by CTA training of vulnerable predators.