Overbrowsing, and decline of a population of the koala, Phascolarctos cinereus, in Victoria. I. Food preference and food tree defoliation

Abstract

Tree usage by koalas as a measure of foliage preference was analysed for 2 yr in an open forest near Walkerville, Victoria, containing 3 Eucalyptus species. At the start of the study, there was significant defoliation of E. ovata. The koalas showed a significant preference for this species, which became increasingly defoliated as the study progressed. The preference for E. ovata decreased in the second year of the study, probably as a result of a decline in available foliage. It also changed seasonally, with koalas showing a stronger preference for E. ovata in autumn and winter than in spring and summer. The preference for E. radiata and E. obliqua was greater in summer, when these species were producing abundant new growth. It is suggested that the koalas select foliage so as to maximize their intake of crude protein.