Roads and water availability influence the occurrence of koalas (Phascolarctos cinereus) in secondary habitat: a multiscale approach

Abstract

Given the high proportion of Earth’s ecosystems already anthropogenically modified, especially through clearing, it is critical we determine whether species can persist outside of their primary habitat as a means of ensuring population persistence in the remaining landscape. The koala (Phascolarctos cinereus) has been heavily impacted by habitat loss through clearing, and recently upgraded to endangered across its eastern distribution. It is timely to understand what variables may influence the occurrence of koalas in secondary habitat, which can then guide conservation efforts. We surveyed 959 sites with detection dogs to determine the occurrence of koalas through the presence of scats. Using GLMMs, we accounted for environmental and anthropogenic variables that may influence koala occurrence, meanwhile focusing on the use of secondary eucalyptus forests at multiple spatial scales (250, 500, 1500 m radii). Overall koala occurrence was negatively associated with secondary eucalyptus forests compared to primary forests, while there was no effect of total forest area present at any scale. However, we found interactive effects between secondary forest and (1) distance from the closest major road at the smallest landscape scale (250 m radii) and (2) water area at the larger landscape scales (500 m, 1500 m radii). This suggests that occurrence of koalas in secondary forests are predicted to increase when the distance to major roads, and the water area, increase. While protecting primary eucalyptus forests should always be a prioritisation for the conservation of koalas, our results emphasize the important role that secondary eucalyptus forests can play in conservation, as long as these are carefully considered in the landscape context to maximise restoration investments.