Mass-corrected field metabolic rates of free-ranging male koalas in central Queensland, Australia, varied between 0.329 MJ kg0.75 day-1 in summer and 0.382 MJ kg0.75 day-1 in winter. Field water influx measured 50.8 mL kg-0.8 day-1 in winter, increasing to 59.9 mL kg0.8 day-1 in summer for the same koalas, and was positively correlated with values for leaf moisture of food. Winter rates of water influx for koalas from Springsure were lower than those recorded for koalas from Victoria for the same period of the year. Mass-corrected feeding rates were lower in summer than winter; wet food intake was significantly lower than reported for similar sized female koalas from Victoria. The preferred browse was Eucalyptus crebra in winter and E. tereticornis in summer. Our study indicates that in central Queensland seasonal changes in diet selection by male koalas reflect increased energy requirements in winter and increased water requirements in summer.

The field metabolic rates (FMR) and water fluxes of Varanus scalaris were measured during the wet and dry seasons by the doubly‐labelled water technique. Seasonal measurements of standard (night‐time) metabolism (SMR) and resting (daytime) metabolism (RMR) were made in the laboratory at 18, 24, 30 and 36°C, and maximal oxygen consumption was measured at 36°C on a motorized treadmill. This population was active throughout the year. In the wet season, the mean FMR was 7.8 kJ day−1 (128.0 kJkg−1 day−1; mean mass = 66.4 g, n= 13), and during the dry season the mean was 5.0 kJ day−1 (67.6 kJ kg−1 day−1; mean mass = 77.4 g, n= 17). The mean water flux rates for these animals were 3.6 and 1.2 ml day−1, respectively (60.4 and 16.6 ml kg−1 day−1). The seasonal means of FMR and water flux were significantly different by ANCOVA (P < 0.0001). Measurements of SMR and RMR were significantly higher in the wet season (ANCOVA: P < 0.0001), but we found no difference in the maximal oxygen consumption between seasons (ANCOVA: P= 0.6). The maximal oxygen consumption of the lizards on the treadmill (2.9 ml min−1= 1.8 ml g−1 h−1), mean mass = 97.4 g, n= 16) was 20 times that of the SMR at the same temperature during the dry season, and 11 times that of the SMR during the wet season. The seasonal differences in FMR were attributable to: changes in SMR (12.2%) and RMR (16.4%); differences in night‐time body temperatures (11.3) and daytime body temperatures (16.4%); and activity (broadly defined to include locomotion, digestion, and reproductive costs (43.7%).

Milk samples were obtained at regular intervals throughout lactation from tammar wallabies (M. eugenii). Total solids represented only 12 % (w/w) of the milk at the commencement of lactation and gradually increased to about 40% at 36 weeks. Milk proteins represented 4% (w/w) of whole milk during the first 18 weeks of lactation, followed by a rapid increase to around 13 % (w/w) at 36 weeks. Sodium and potassium concentrations were high in early samples of milk but declined to minimal values at 30 weeks. The milk was isosmotic to the plasma at all stages.

Water turnover rate (WTR), urine concentration and field metabolic rate (FMR) were examined in house mice, Mus domesticus, permanently inhabiting roadside verge areas and seasonally invading crops in semi-arid wheatlands in South Australia. FMR was approximately proportional to body mass and mean values varied from 4.8 ml CO gh (2.9 kJ gd) in autumn and winter, to 7.0 ml CO gh (4.2 kJ gd) in maturing crops during spring. WTR was independent of body mass, indicating that larger mice were selecting a diet containing moister foods. WTR was low in summer and high in winter, and in mice from crops varied from 165 ml l body water d (122 ml kgd) to 1000 ml ld (725 ml kgd). Seasonal changes in WTR were less extreme on the roadside, where a greater diversity of food was available. In the crops, breeding occurred throughout summer during two of three years, but the population increased only in the one summer when mice had marginally higher WTR. On the roadside breeding and population growth were continuous during summer, except in a drought year. Avcrage urine concentration was inversely related to WTR, and varied from 2.0 to 4.8 Osm l. The data indicate that the water conserving abilities of mice equal those of many desert rodents. The water conserving abilities of mice living in crops during summer were fully extended, and in some years aridity limited breeding success and population levels. The degree of moisture stress to which mice are exposed during summer appears to depend not only on rainfall but also on other factors such as availability of food and shelter, and the level of weed infestation in crops.

Milk consumption rates of young tammar wallabies, Macropus eugenii, were measured during the first 32 weeks of lactation by means of 22*Na turnover. Milk consumption rates were low during the first 18 weeks or so of lactation, rising from 1.2 to 9.0 ml d-'. Milk consumption rose to 43 ml d-' at 30 weeks post-partum. Changes in milk consumption were paralleled by increases in the size of mammary glands and weight gain by the sucklings. The mass gain for each millilitre of milk consumed (crude growth efficiency) averaged 0.23 g ml-I during the first 26 weeks of lactation, but then increased to more than 0.35 g ml-'. The increased growth efficiency was associated with massive increases in the lipid and energy content of milk from 26 weeks onwards. The conversion efficiencies of milk protein and energy to body materials were intermediate (55-87%, 23-36%, respectively) to those of other mammals, which suggests that the slow growth of pouch young during the first 17 weeks of lactation is the result of restricted milk production by the mother. Milk production and the growth of young were closely correlated with maternal mass (r=0.96; r=0.80, respectively) at 16 weeks post-partum.