Overbrowsing, and decline of a population of the koala, Phascolarctos cinereus, in Victoria. III. Population dynamics

Abstract

The demography of a population of koalas at Walkerville, Victoria, which was severely defoliating its preferred food trees was monitored for 3 yr from Aug. 1977. Population density declined from 3.0 animals/ha in winter 1978 to 0.7/ha in winter 1980. Population density also fluctuated seasonally, with a max. in autumn/winter and a min. in spring. Fertility rate was low compared with that of other populations and declined over the period of the study. This was due to depressed fertility among the younger females and substantial infertility among the older females. Mortality was heaviest in the winter, and the majority of carcasses found were of old females. A sharp decline in population density, caused by the dispersal of many of the residents, occurred in winter 1980 when the defoliation of the preferred food species, Eucalyptus ovata, was most advanced.