A diversity of rodents and dasyurid marsupials in arid Australia occupy refuges; discrete areas of the landscape in which populations persist during periods of low resource availability (‘busts’). Refuges are assumed to provide shelter from predators, suitable microclimate for thermoregulation and food resources during the low phase of population cycles. During bust periods, small mammal populations that use refuges persist in high density, and individuals maintain body condition and reproduction. These findings imply that refuge populations have access to a reliable and high-quality food supply; and this is partly borne out by one diet analysis that shows a switch from winter-germinating to summer-germinating short-lived plants according to seasonal availability. Beyond this, primary productivity and consumer relationships remain poorly known for arid Australia, meaning we are not well-placed to predict climate change impacts on the food axis of mammal refuges. We address this issue by quantifying the vegetation dynamics at refuges of the plains mouse (Pseudomys australis) on cracking clay and gibber plains in the western Simpson Desert. In particular, we focus on changes in the plant assemblage across gradients of P. australis site occupancy (refuge/non-refuge sites) and population abundance (over the boom-bust cycle), using data from a decade-long monitoring program.
Results/Conclusions
We found that vegetation and P. australis gradients are strongly correlated in space and time. Moreover, the short-lived flora was identified as the key element of the population cycle of this rodent species: it is exclusively utilized during the bust phase (extreme drought) and it characterizes refuge sites during the boom phase (‘big wet’ years). Of concern therefore, these winter- and summer-growing specialist plants are expected to be strongly disadvantaged in the upcoming decades respectively by predicted reduced winter rainfall and hotter temperatures and increased evapotranspiration in summer.