SEASONAL FIELD ENERGETICS AND WATER FLUXES OF THE LONG-NOSED POTOROO (POTOROUS-TRIDACTYLUS) IN SOUTHERN VICTORIA

Field metabolic rates (FMRs) and water-flux rates of free-living male and female long-nosed potoroos (Potorous tridactylus) were measured in two seasons near Warrnambool in southern Victoria, Australia, using t he doubly labelled water technique. Potoroos, which weighed about 835 g, expended 30% more energy (590 kJ day(-1)) in early spring than they did in midsummer (463 kJ day(-1)), despite mean minimum temperatures in the two seasons differing by only 4 degrees C. We did not find any difference in the FMRs of males and females even though all females ca rried pouch young or had young at foot. The mean water flux rates foll owed a similar seasonal trend to that of FMR with the summer mean infl ux rate (131 mL day(-1)) being 30% lower than that in spring (174 mL d ay(-1)). This difference in water-turnover rate may reflect changes in the seasonal water status of the environment. Hypogeous fungi constit ute a major part of the diet of potoroos and the role played by this f ood source in supplying amino acids is discussed.