NUTRIENTS, ANTINUTRIENTS AND LEAF SELECTION BY CAPTIVE KOALAS (PHASCOLARCTOS-CINEREUS)

The preferences of koalas for Eucalyptus foliage, as ranked by keepers at 13 wildlife parks and zoos in New South Wales, were compared with the content of a number of nutrients and antinutrients (allelochemical s) in samples of the leaves offered to koalas in each park. Statistica l analyses indicated that no single factor separated the four preferen ce groups used, but that koalas selected foliage that contained at lea st a minimal or threshold level of water (approximately 55%) (P=0.028) and essential oils (approximately 2% of dry matter) (P=0.044). The es sential oils of the two most preferred groups had a higher proportion of volatile monoterpenes (the most aromatic oil fraction) (P<0.001) an d a lower proportion of sesquiterpenes (P<0.001) than those of the two least preferred groups. The two most preferred groups also had a high er (P=0.008) ratio of nitrogen (N) to neutral-detergent fibre (NDF), a nd the most preferred group had the lowest (P=0.033) content of conden sed tannins (CT) and the highest (P=0.010) ratio of N to CT. Thus, the ratios of N to NDF and CT are likely to be important predictors of ko ala acceptance of Eucalyptus foliage, and probably its nutritive value . It also appears that koalas may use eucalypt oils as a positive feed ing cue, and that they prefer oils with a relatively high proportion o f volatile monoterpenes.