Assessing the predation potential of the toad-eating Taiwan keelback (Rhabdophis formosanus Maki, 1931) on the toxic invasive cane toad (Rhinella marina Linnaeus, 1758)

Context Toxic invasive prey poses a threat to consumers by causing physiological disorders and death. Some consumers use toxic prey as food and sequester toxins for chemical defense. However, studies on the predation potential of toxic invasive prey by those consumers are limited. Aims We assessed the predation potential of the Taiwan keelback snake (Rhabdophis formosanus), a species that sequesters toxins from native toads, on an invasive cane toad (Rhinella marina). Methods We conducted prey preference tests based on odor and visual cues, and a toxin tolerance test. Key results Rhabdophis formosanus showed the strongest preference for its typical toxin source, Central Formosa toad (Bufo bankorensis), based on odor cues, but for the invasive Rhinella marina, based on visual cues. In the toxin tolerance test, juvenile Rhabdophis formosanus exhibited a marked decline in locomotor performance and died when administered a dose equivalent to one quarter of the quantity of toxin contained in the largest toad it could consume; adults survived without substantial impairment of physiological functions. When administered a higher dose equivalent to half the toxin present in the largest toad that they could consume, all Rhabdophis formosanus experienced severe impairment in locomotor performance and eventually died. Conclusions Rhabdophis formosanus may prey on Rhinella marina when encountered and small toads can be consumed; however, large toads may cause poisonous death. Implications To conserve Rhabdophis snakes and other native consumers, assessing their predation potential when sympatric with Rhinella marina, and evaluating the potential impacts of this invasive toad are essential.