A native dasyurid predator (common planigale, Planigale maculata) rapidly learns to avoid a toxic invader

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Journal Article
Austral Ecology, 2008, 33 (7), pp. 821 - 829
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Interactions between invasive species and native fauna afford a unique opportunity to examine interspecific encounters as they first occur, without the complications introduced by coevolution. In northern Australia, the continuing invasion of the highly toxic cane toad Bufo marinus poses a threat to many frog-eating predators. Can predators learn to distinguish the novel toxic prey item from native prey (and thus, avoid being poisoned), or are longer-term genetically based changes to attack behaviour needed before predators can coexist with toads? To predict the short-term impact of cane toads on native predators, we need to know the proportion of individuals that will attack toads, the proportion surviving the encounter, and whether surviving predators learn to avoid toads. We quantified these traits in a dasyurid (common planigale, Planigale maculata) that inhabits tropical floodplains across northern Australia. Although 90% of naïve planigales attacked cane toads, 83% of these animals survived because they either rejected the toad unharmed, or killed and consumed the prey snout-first (thereby avoiding the toxin-laden parotoid glands). Most planigales showed one-trial learning and subsequently refused to attack cane toads for long time periods (up to 28 days). Toad-exposed planigales also avoided native frogs for up to 9 days, thereby providing an immediate benefit to native anurans. However, the predators gradually learnt to use chemical cues to discriminate between frogs and toads. Collectively, our results suggest that generalist predators can learn to distinguish and avoid novel toxic prey very rapidly - and hence, that small dasyurid predators can rapidly adapt to the cane toad invasion. Indeed, it may be feasible to teach especially vulnerable predators to avoid cane toads before the toads invade, by deploying low-toxicity baits that stimulate taste-aversion learning. © 2008 The Authors.
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