Thermoregulation strategies differ for large macropods during high temperatures

Abstract

In semi-arid drylands, landscape features such as water and trees are vital for individuals when reducing heat stress. In Australia, such landscapes have witnessed widespread canopy loss and considerable shifts in water availability due to anthropogenic processes, and are subject to greater frequencies of extreme temperatures. We explored the use of dammed watercourses and excavated earth tanks, and tree shade in two large macropod species, eastern grey kangaroos (Macropus giganteus) and red kangaroos (Osphranter rufus) in the semi-arid drylands of south-western Queensland. Using a thermal drone, camera traps, and temperature sensors, we examined the relationship between temperature, and water and canopy shade use by both species. The likelihood of kangaroos being observed in the sun was negatively correlated with temperature, with the likelihood of observing eastern grey kangaroos in the sun dropping below 50 % when temperatures exceeded 28 °C, and 17 °C for red kangaroos. Probability of detecting kangaroos in the shade was positively correlated with temperature, with red kangaroos more strongly selecting shade than eastern grey kangaroos. For eastern grey kangaroos, we observed greatly increased activity at waterpoints when daily maximum temperatures exceeded 28 °C, with a preference for dammed watercourses over excavated earth tanks. Only a weak trend of using dammed watercourses at high temperatures (>36 °C) was detected for red kangaroos. As higher temperatures become more frequent due to climate change, our results suggest that the capacity of wildlife to persist may increasingly depend on the provision and maintenance of landscape features such as water and canopy shade.