Diana O. Fisher

Theory suggests that the distributions of threatened species do not generally contract to the species' core habitat. Rather, surviving populations that decline to range edges often persist in suboptimal habitat because it is least affected by their important threats. The northern quoll ( Dasyurus hallucatus ) is an endangered carnivorous marsupial that occurs in patchy populations across northern Australia, now almost entirely in rugged habitats. The overall goal of this study was to assess differences in quality across available habitat types to determine if rugged habitats do constitute higher quality habitat for northern quolls, as no field data are yet available to test this hypothesis. Through fieldwork in the Pilbara (Western Australia), we assessed habitats based on vegetation, shelter availability, and prey availability. While we did not find significant differences in prey availability across habitats, we found differences in the availability of potential dens and temporary shelters suggesting that shelters are of higher abundance in rocky‐riparian and rocky habitats. Habitat associations of prey suggest that northern quolls in rocky‐riparian habitats may feed or subsidize their diets with prey from adjacent habitats including grasslands, which carry risk of predation by feral cats in our study area. Our results agree with GIS‐based studies from the Pilbara, namely rugged habitats currently represent the highest quality habitat for northern quolls there. There are two nonexclusive hypotheses explaining the contraction of quolls to rocky habitats; we found stronger support for the den hypothesis than the prey availability hypothesis, suggesting that shelter availability is an important current determinant of habitat quality for northern quolls in the Pilbara. Our study helps to highlight the role of den availability and temporary cover as a crucial component of habitat quality for northern quoll presence and abundance across the landscape under current conditions.