Avoiding the last supper: parentage analysis indicates multi-generational survival of re-introduced ‘toad-smart’ lineage

Invasive species are a leading cause of animal extinctions. It is difficult to eradicate established and widespread populations of invaders, so we need novel approaches to reduce their impact on imperilled wildlife. In Australia, the toxic cane toad Rhinella marina has caused local extinctions of northern quolls Dasyurus hallucatus. Quolls lack immunity to toad toxins, and die after attacking adult toads. Using a novel approach, we modified quoll behaviour by feeding them small, non-lethal toads laced with a nausea-inducing chemical. Quolls that consumed the baits became ill, and subsequently ignored toads. We reintroduced these ‘toad-smart’ quolls to Kakadu National Park to determine whether aversion training could be an effective conservation tool. To measure the success of our innovation, it was important that reintroduced quolls survived to reproduce in a toad-infested landscape. We used parentage analysis to confirm the maternity of 12 wild-born quolls. ‘Toad-smart’ female quolls not only survived to reproduce, but their children and grandchildren survived as well. Training a single cohort of quolls yielded a long-term conservation benefit, without requiring continued conservation effort or eradication of the toxic invader.