Data from: Topographic ruggedness and rainfall mediate geographic range contraction of a threatened marsupial predator

Aim: Species range contractions are increasingly common globally. The
niche reduction hypothesis posits that geographic range contractions are
often patterned across space owing to heterogeneity in threat impacts and
tolerance. We applied the niche reduction hypothesis to the decline of a
threatened marsupial predator across northern Australia, the northern
quoll (Dasyurus hallucatus). Location: Northern Australia Methods: We
assembled a data base containing 3178 historic and contemporary records
for northern quolls across the extent of their distribution dating between
1770 and 2019. Based on these records, we estimated changes in the
geographic range of the northern quoll using α-hulls across four main
populations. We then examined how range contractions related to factors
likely to mediate the exposure, susceptibility, or tolerance of northern
quolls to threats. Result: The extent of range contractions showed an
east-west gradient, most likely reflecting the timing of spread of
introduced cane toads (Rhinella marina). There were clear changes in
environmental characteristics within the contemporary compared to the
historic geographic range, with the most substantial occurring in
populations that have suffered the greatest range contractions. The
contemporary range is comprised of higher quality habitats (measured using
environmental niche models), characterized by higher topographical
ruggedness and annual rainfall, and reduced distance to water, compared to
the historic range. Main conclusions: Changes to range and niche likely
reflect the capacity of complex habitats to ameliorate threats (namely
predation and altered fire regimes), and access to resources that increase
threat tolerance. This study highlights the multivariate nature of
ecological refuges, and the importance of high-quality habitats for the
persistence of species exposed to multiple threats. Our methods provide a
useful framework which can be applied across taxa in providing valuable
insight to management.