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.
Milk samples were collected from captive common ringtail possums, Pseudocheirus peregrinus, throughout lactation and from free-living animals during phase 3 of lactation (weeks 15-30 post partum). Both field and captive animals lactated for approximately 30 weeks. In comparison with the milks of other marsupial species, ringtail possum milk was relatively dilute and low in lipid. During phase 2 of lactation (up to week 14) solids represented around 16% (w/w), comprising mostly carbohydrate and protein, increasing to 25% (w/w) at the onset of pouch emergence. During the period of pouch vacation (weeks 15-18) the carbohydrate concentration declined and protein and lipid concentrations peaked. Sodium and potassium concentrations throughout lactation were around 25 mm and 22 mm respectively. Calcium and magnesium levels were around 1.8 g per L and 131 mg per L respectively. Milk carbohydrates consisted mainly of oligosaccharides during phase 2 of lactation and these were replaced by the disaccharide lactose during phase 3 of lactation. The pattern of change in the composition of ringtail possum milk during phase 2 was similar to that shown by those of other marsupials, but during phase 3 the milk had higher levels of carbohydrate and lower levels of lipid than that of other marsupials. Differences in the composition of milk from free-living and captive animals suggest that diet composition may affect the concentration of milk protein and milk fat within a species.
Water flux and field metabolic rate (FMR) were measured by the doubly labelled water (DLW) method in free-living male and female rufous rat-kangaroos Aepyprymnus rufescens near Drake in northern New South Wales. The mean FMR of 499 kJ kg-1 day-1 was similar in winter and summer even though the difference in mean minimum temperatures between the two seasons was 20-degrees-C. Furthermore, we did not find any differences in FMR between males and females even though several females carried large pouch young or had young-at-foot. A poor understanding of the diet and the behavioural ecology of A. rufescens makes ft difficult to explain the similarities between sexes and seasons.
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