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

Abstract

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 database containing 3,178 historic and contemporary records for northern quolls across the extent of their distribution dating between 1778 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.

Patterns of niche contraction identify vital refuge areas for declining mammals

“…ecological niche model, extent of occurrence, mammal, niche hypervolume, niche reduction hypothesis, range contraction, refuge, species decline, threatening process to identify regions of conservation importance. Specifically, we address the following questions: To answer these questions, we use historical and contemporary records of species occurrences to quantify changing spatial patterns and niche characteristics through time, following an approach similar to that used by Moore et al (2019). Consistent with the niche reduction hypothesis (Scheele et al, 2017), we predict that the availability of refuge habitats, where threats are reduced or absent, can be readily identified in some or all species of interest.…”

“…To answer these questions, we use historical and contemporary records of species occurrences to quantify changing spatial patterns and niche characteristics through time, following an approach similar to that used by Moore et al. (2019). Consistent with the niche reduction hypothesis (Scheele et al., 2017), we predict that the availability of refuge habitats, where threats are reduced or absent, can be readily identified in some or all species of interest.…”

Artificial refuges to combat habitat loss for an endangered marsupial predator: How do they measure up?

“…The northern quoll ( Dasyurus hallucatus ) is an Australian marsupial mesopredator (~520 g) that has declined substantially over the past 200 years (Braithwaite & Griffiths, 1994; Moore et al, 2019). Range contractions of up to 75% have been recorded (Moore et al, 2019) due to habitat loss, introduced predators (namely the feral cat, Felis catus , and red fox, Vulpes vulpes ), altered fire regimes, and poisoning by the introduced cane toad ( Rhinella marina ; Ibbett, Woinarski, & Oakwood, 2018; Moore et al, 2019). The species is listed as endangered by the IUCN and has a “decreasing” population trend (Oakwood, Woinarski, & Burnett, 2016).…”

“…The species is listed as endangered by the IUCN and has a “decreasing” population trend (Oakwood, Woinarski, & Burnett, 2016). The Pilbara region of Western Australia is the last remaining stronghold for the northern quoll, likely due to the absence of cane toads (Moore et al, 2019; Woinarski, Burbidge, & Harrison, 2014). Yet, this stronghold is far from secure, with predation by feral cats threatening Pilbara quoll populations (Cramer et al, 2016; Hernandez‐Santin, Goldizen, & Fisher, 2016), and >91% of the region under mining lease (Environmental Protection Authority, 2014).…”

Skull shape of a widely distributed, endangered marsupial reveals little evidence of local adaptation between fragmented populations

“…They are now separated by major biogeographic breaks into four mainland populations with no apparent gene flow (Hill & Ward, 2010) and several island populations (Woinarski et al., 1999). Northern quolls are also a suitable study system for this investigation because they inhabit a wide range of habitats, ranging from rainforests to deserts (Begg, 1981; Moore et al., 2019; Oakwood, 2002). They are opportunistic foragers of small vertebrates, invertebrates, fruit, and carrion (Dunlop, Rayner, & Doherty, 2017).…”