Continuous monitoring of feeding by koalas highlights diurnal differences in tree preferences
Karen J. MarshA,C, Ben D. MooreB, Ian R. WallisA and William J. FoleyA
ADivision of Evolution, Ecology and Genetics, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia.
BHawkesbury Institute for the Environment, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia.
Context It is difﬁcult to measure feeding rates for most wild nocturnal mammalian herbivores. Thus, although koalas are a popular species to study, we have a poor understanding of their activity patterns and feeding ecology. Researchers often assume that the trees that koalas occupy during the day indicate feeding preferences, but they may better reﬂect preferred resting sites.
Aims We recorded the activities of koalas, with an emphasis on their feeding, particularly when they fed, the trees that they fed from, the number of meals they consumed and the variability in these measurements.
Methods We continuously monitored eight koalas by audio-and radio-telemetry for 14 consecutive 24-h periods each. We followed two koalas at a time and recorded the trees they visited, when,where and how long they fed, and the size and nutritional composition of the trees in the landscape.
Key results Individual koalas varied in how many trees they visited, how many meals they ate and how long they spent feeding during each 24-h period. They preferred Eucalyptus globulus trees during the day, but fed mainly at night, with a preference for E. viminalis. The trees that koalas visited during the day were larger than those that they visited at night. Conclusions. The trees that koalas occupied during the day were poor indicators of their diet preferences, whereas the daily feeding activities of individual koalas varied widely.
Implications Predicting a koala’s diet from the trees it occupies during the day is fraught with error. Although the trees that koalas rest in are important in the species ecology for reasons other than feeding, we should refrain from using them to predict an animal’s diet. Because feeding activity is difﬁcult to measure, it is probably best done in directly by analysing leaf-cuticle fragments or waxes in faeces. The substantial day-to-day variation in koala activities also indicates that behavioural and physiological studies of koalas require long monitoring periods – a week or longer.