We are experiencing a global biodiversity and climate crisis that is rapidly causing
the extinction of species. Mammal species have been disproportionately affected;
however, this trend is considerably worse in Australia. Since Australia’s occupation
by Europeans, 34 mammal species have been declared extinct. Australian
mammals in deserts are particularly at risk of extinction. Many arid zone mammals
have specialised adaptations to their hostile, unpredictable ecosystems. For
example, they use thermally insulative refuges, prefer habitats that reduce predation
risk, or have large home ranges and broad diets to maximise energy intake.
Understanding these adaptations is essential for informed conservation
management. However, little ecological data is known for the sandhill dunnart,
Sminthopsis psammophila, an endangered and charismatic marsupial that now
remains within just a few natural refugial habitats in Australia’s southern deserts. To
address conservation biology knowledge gaps, an integrated, evidence-based
approach (i) quantified the diurnal and nocturnal ecology of S. psammophila in the
Western Australian Great Victoria Desert (WAGVD), (ii) estimated the past, present
and future distributions of S. psammophila throughout Australia, (iii) examined the
key threats to S. psammophila - particularly wildfires and anthropogenic climate
change - and (iv) proposed conservation management solutions for a) S.
psammophila and b) sympatric arid zone species. Between 2015 and 2019, radio
tracking and global positioning system (GPS) technologies examined the sheltering,
foraging, dietary and habitat preferences of S. psammophila in the WAGVD. In
contrast to its previously reported habitat preferences, S. psammophila preferred
burrowing within long unburned (32+ years since a wildfire) spinifex (Triodia spp.)
grassland habitats. Dense lower stratum swale, sand plain and dune slope habitats
were preferred, whereas habitats lacking spinifex and open dune crest habitats were
rarely used. Hence, wildfires were identified as a significant threat to the species.
The sheltering preferences of S. psammophila agreed with the premise that small
desert mammals often use shelters with thermal advantages and anti-predation
benefits, such as burrows, Lepidobolus deserti hummocks and logs. Conversely,
spinifex hummocks were not found to be insulative against extreme temperatures
and were not preferred. The foraging adaptations of S. psammophila agreed with
the premise that arid zone species often have large home ranges to exploit resource
patches or islands. The 100 % home ranges of S. psammophila [mean: 70 ha;
range: 6-274 ha; minimum convex polygon (MCP)] were influenced by sex and
reproductive status. In addition, a Formicine-rich diet indicated that ants are an
important dietary resource for S. psammophila. Species distribution models (SDMs)
predicted the past, present, and future distributions of S. psammophila, evaluated
the environmental parameters that determine the species’ distribution and identified
habitats of high conservation value. The past model supported evidence that S.
psammophila was widespread but has recently contracted to more climatically
favourable areas of its geographic range. Ground-validation of the present model’s
predictions discovered a population 150 km north of the species’ known range.
Future models identified that climate change is a potential catastrophic threat for S.
psammophila. By 2050, under Representative Concentration Pathway (RCP) 8.5
(our current pathway) there is a predicted 95 % reduction in suitable habitat for S.
psammophila in the WAGVD. By 2070 (RCP 8.5), only the Eyre Peninsula
population may remain viable and the continental distribution of S. psammophila
may contract by up to 80 %. However, this contraction is predicted to be halved if
global greenhouse gas emissions peak in 2040 then reduce (RCP 4.5). Due to
specific habitat preferences for long unburned habitats, S. psammophila is further
restricted within its climatically and geographically suitable range. As a semi-arid
specialist, it is also vulnerable to drought-related population crashes. Hence, S.
psammophila should remain listed as endangered at the state and federal level, and
its status should be revised by the International Union for Conservation of Nature.