Tree species preferences of koalas (Phascolarctos cinereus) in the Campbelltown area south-west of Sydney, New South Wales

Abstract

Tree species preferences of a koala population inhabiting a small area of forest and woodland in the Campbelltown area, south-west of Sydney, were investigated over a two-year period. In total, 2499 trees from 45 independent field sites were assessed, with tree species preferences determined on the basis of a comparative analysis of proportional data relating to the presence/absence of koala faecal pellets. The results established that grey gum (Eucalyptus punctata) and blue-leaved stringybark (E. agglomerata) were most preferred by koalas in the study area, but only when growing on shale-based substrates. The preferential utilisation of E. punctata and E. agglomerata on substrates derived from shales, compared with that recorded for the same species on sandstones, suggests that their use by koalas was influenced by differences in nutrient status between substrates. Regression analyses further identified a trend for use of at least one of the preferred species (E. punctata) to be more commonly associated with larger trees. Results are discussed in terms of their relevance to issues of resource availability and the need to reconsider, by way of a hierarchical approach, the use of food trees by koalas generally. The presence of E. punctata and E. agglomerata and their occurrence in conjunction with shale-based substrates are considered to be important limiting factors affecting the present-day distribution and abundance of koalas in the Campbelltown area.