Get smart: native mammal develops toad-smart behavior in response to a toxic invader

Abstract

Although invasive species can cause major declines in native populations, some individuals in a native population are better equipped to deal with the threat than others. Existing trait variation—especially in highly flexible behavioral traits—may thus buffer populations and allow natural selection to proceed. Cane toads (Rhinella marina) have caused dramatic declines in native Australian predators, which unwittingly attack the poisonous toads. The northern quoll (Dasyurus hallucatus) is one such predator, with declines and local extinction of quoll populations typically occurring rapidly after toads arrive. Despite this, some quoll populations persist in areas where toads have been present for ≥70 years. Here, we compare northern quolls from toad-infested and toad-free areas to test whether this persistence is enabled by behavioral traits. We demonstrate that northern quolls from long-term toad-infested areas have indeed become “toad-smart,” spending significantly less time investigating a toad compared with a control prey item, and limiting this investigation time to investigatory rather than attacking behavior. By contrast, quolls from toad-naive populations vary in their response to toads, with many exhibiting attack behavior. These results demonstrate that behavioral variation exists within naive populations and the few persisting northern quoll populations in toad-infested areas have naturally developed toad-smart behavior. Population modeling suggests this behavior likely persists across generations. Although the mechanism is unknown, the observed shift in toad-smart behavior may be due to rapid adaption, and if so could become a vital tool for conserving this endangered species.