Studies on Water Metabolism of the Hill Kangaroo, Macropus Robustus (Gould), in Northwest Australia

Abstract

The hill kangaroo, Macrophus robutus, is able to survive in hot and arid conditions not because of its ability to concentrate urine, but because it avoids high air temperatures by sheltering in caves where it can withstand considerable dehydration. Urine concentrations were high throughout the year studied. The sodium concentration relative to the potassium concentration was greater in the hot dry periods. Plasma sodium concentrations were similar in field animals at all times of the year and not significantly different from animals kept in yards with unlimited water. Severe dehydration in the yards resulted in an elevation of the plasma sodium concentration. Comparison of the urine area concentrations of animals from areas of high and low protein pasture suggests that this was directly dependent on protein value of the food grasses in the area where the animals lived. When kept on a dry diet and no water the animals survived a water loss corresponding to 20 to 30% of their body weight during five days. The average volume of water consumed at each drink by field animals during the hot dry time of the year corresponded to 12% of their body weight, although it is known that few drink as frequently as once in five days.