What Koalas Can Tell Us About Their Home Range Selection
The Hastings-Macleay Koala Recovery Partnership are currently undertaking a radio-tracking study on 15 koalas to determine habitat usage and home ranges of koalas on the coastal floodplain. The preference of koalas for certain feed trees within a local environment has long been recognised. This has led to an understanding that koala habitat can be defined by this factor alone with NSW legislation currently identifying koala habitat as areas of land on which >15% of the trees present are koala feed trees (see State Environmental Planning Policy No. 44 Koala Habitat Protection). Increasingly, koala researchers are recognising that ‘mesic refuge areas’ (cool, shady places such as along drainage lines) are also important for koalas. Because such shelter areas may be dominated by rainforest trees or paperbarks, as opposed to recognised koala food trees, they are often not formally classified as koala habitat. Similarly, some areas of koala’s home ranges may be important for connectivity between feeding areas, or for socialisation reasons. Whilst these areas may also not support >15% koala food trees they are still important for the proper functioning of a koala’s home range. Finally, on the coastal floodplain, the rich, moist soils ensure that adequate leaf nutrition is available for a hungry koala, meaning that koalas are able to extract enough of their dietary requirements from a relatively fewer number of standing feed trees. In some cases where the percentage of koala feed tree is <15%, such areas are not captured as koala habitat under many legislative controls- even though they are an important part of a koala’s home range. Finally, it is important to understand if koalas ‘partition’ their habitat in the different seasons of the year. Understanding whether this occurs on the coastal floodplain is important as surveys for development purposes could otherwise lead to the assumption that koalas are not present (and hence the area is not koala habitat), when in fact, they are just not present at that time of the year. The radio-tracking study aims to combine the knowledge about koala’s home ranges with detailed vegetation surveys, to provide empirical evidence around these issues to inform policy and planning.
The study works in close collaboration with the Port Macquarie Koala Hospital. All koalas captured are given health screenings (while under anaesthesia) at the Koala Hospital. The study therefore also gives an understanding of koala health in areas more remote from human development
Data from the study has revealed that even on the fertile soils of the coastal floodplain, some koalas have surprisingly large home ranges with male koalas occupying over 100 ha. The data will be compiled in 2019 and then published. Watch this space for further updates!