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Red kangaroos (Macropus rufus) occur widely in deserts and arid rangelands. Eastern grey kangaroos (M. giganteus) are a more mesic species but have spread into the arid rangelands in the past decades. Additional stock watering sites are suggested to have facilitated this movement. We examined the impact of environment, behaviour and diet on field water use by M. rufus and M. giganteus at Fowlers Gap Arid Zone Research Station in western NSW. The time was late summer and during the study the weather was fine and clear, with mean daily maximum Ta being 31 °C (range, 29-33 °C) and mean daily minimum Ta being 18 °C (range, 14-21 °C).
M. giganteus had marginally higher water turnovers (72 ml/kg.d against 58 ml/kg.d); however, they drank much more frequently than M. rufus. Differences between the species were also found in urine concentrations. Patterns of behaviour and diet selection were also noted. Although a specific reason could not be given for the higher water use of eastern grey kangaroos, the provision of additional stock watering sites likely facilitated their spread into the arid rangelands.