Queensland northern quolls are not immune to cane toad toxin

Context The release of the highly toxic South American cane toad (Bufo marinus) to the toad-free Australian continent in 1935, and their subsequent rapid spread over large areas of tropical Australia, has resulted in a massive decline of predators such as yellow-spotted goannas (Varanus panoptes) and northern quolls (Dasyurus hallucatus). In spite of dramatic declines of northern quoll populations in the Northern Territory, a few populations still persist in areas of Queensland where northern quolls have co-existed with toads for several decades. Aims To determine whether the remaining quoll populations in Queensland have evolved resistance to cane toad toxins. Methods The extracellular H1–H2 domain of the a1 subunit of the sodium–potassium-ATPase gene was sequenced in four Queensland as well as four Northern Territory quolls. The transcribed sodium–potassium-ATPase enzyme from this gene is specifically targeted by toad toxins. Key results In all of the eight quolls, the sequences representing the 36 bp of the H1–H2 domain of the a1 subunit of the sodium–potassium-ATPase gene were identical. Conclusions Our results showed that Queensland quolls have not evolved an increased resistance to the toad toxins. We therefore suggest that the persistence of northern quolls in a few toad infested areas of Queensland could to be due to a combination of optimal habitat quality, and concomitant large quoll numbers, as well as an aversion to feeding on these highly toxic amphibians. Implications We suggest that a sample of northern quolls from the Queensland populations should be captured and their response, as well as that of their offspring and grand-offspring, to cane toads should be investigated to guide management of this declining species.