Seasonal-Variation in Water Flux, Field Metabolic-Rate and Food-Consumption of Free-Ranging Koalas (Phascolarctos-Cinereus)

Abstract

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.

Climate change and the koalaPhascolarctos cinereus: water and energy

“…These koalas (average mass males 6.7 kg; females Ellis et al Australian Zoologist volume 35 (2) 5 kg) range around the mine area, on the lease itself and on adjacent grazing, farming and undisturbed property and state forests. The results for winter (July) and summer (December) at Springsure, used for comparison, were as reported in an earlier study (Ellis et al 1995).…”

“…The blood samples were collected in 5 ml sterile vials and frozen at -20 o C. These samples were then analysed as described by Ellis et al (1995).…”

“…Since riparian trees were found to have highest leaf moisture in central and north western Queensland (Ellis et al 1995, Munks et al 1996 it follows that conservation of these areas, which also house the densest aggregations of koalas in drier areas of Queensland (Munks et al 1996, Sullivan et al 20032004), should deliver the best outcome in terms of long term koala persistence. Gordon et al (1988) describe the impact of drought and extreme heat on riparian vegetation and the consequent collapse of the resident koala population in southwestern Queensland.…”

“…Australian Zoologist volume 35 (2) (Degabriele et al 1978;Nagy and Martin 1985), so it was not surprising that some workers concluded water content of leaves to drive tree selection by koalas at warmer times of year (Ellis et al 1995). Since riparian trees were found to have highest leaf moisture in central and north western Queensland (Ellis et al 1995, Munks et al 1996 it follows that conservation of these areas, which also house the densest aggregations of koalas in drier areas of Queensland (Munks et al 1996, Sullivan et al 20032004), should deliver the best outcome in terms of long term koala persistence.…”

The dietary preferences of koalas,Phascolarctos cinereus, in southwest Queensland

“…In subhumid central Queensland, annual records of water content in Eucalyptus foliage showed a trend that water concentrations were higher during summer, the rainy season (Ellis et al 1995). This study found that leaf moisture was significantly higher with the presence of surface water regardless of tree species.…”