The thermal benefits of a mound-burrow system in a semi-desert Australian landscape: will this pebble fortress provide refuge from climate change?

Deserts are expected to warm and dry more than other ecoregions, making it critical to understand how arid-adapted animals might cope with increasing climate change. Plasticity in microclimatic niches created through the extended phenotype have been hypothesized to buffer desert-dwelling organisms from rapidly changing conditions. A unique example of the extended phenotype is the mound-burrow system of the western pebble mouse (Pseudomys chapmani), a small rodent that survives in one of Australias harshest environments. Here, using thermo-loggers and by obtaining mound measurements, we show that the mound-burrow system provides protection from prevailing desert conditions of both searing heat and freezing cold. We show that burrow depth and the height of the parapet around the entrance help maintain stable temperatures by warming in winter and cooling in spring. Burrows also had stable humidity levels relative to external fluctuations. We conclude that this unique pebble fortress is a critical resource that allows the species to persist in an extreme environment. We then applied modelling to assess how global warming has, and may continue to, influence(d) thermoregulation and behaviour, revealing that future summers in this extreme region may require refuge at an unachievable depth. Our study highlights the limits of the extended phenotype in buffering climate change impacts and raises concerns about the future of desert rodent populations in a rapidly warming world.