The effects of lactation on the feeding behaviour and activity patterns of free-ranging female koalas (Phascolarctos cinereus Goldfuss)
M. Logan and G. D. Sanson
Department of Biological Sciences, Monash University, PO Box 18, Clayton, Vic. 3800, Australia.
The free-ranging feeding behaviour and activity patterns of three lactating and two non-lactating female koalas (Phascolarctos cinereus) were investigated using acoustically sensitive radio-telemetry. Lactating females were found to consume more leaf material, masticate more per leaf and at a greater rate, and perform more ingestive and merycism mastications per 24 h than non-lactating females. Results suggest that female koalas are 'income breeders' that compensate for the higher energetic demands of lactation by increasing intake and, to a lesser degree, investing more in each mouthful so as to produce a shift in digesta particle size distribution in favour of more finer particles. Compared with non-lactating females, lactating female koalas were also found to spend more time moving within trees, feeding per 24 h and per bout, and less time resting and sleeping per 24 h, although the proportion of active time spent feeding was similar (-80%). This implies that female koalas adopt a 'time minimizing' strategy whereby activity budgets respond to current requirements. Lactation-compensation mechanisms are compared with those reported for koalas with high tooth wear, and the capacity of aging female koalas to compensate for lactation are discussed.