Modelling mammalian extinction and forecasting recovery: koalas at Iluka (NSW, Australia)
Daniel Lunney1,*, Lisa O’Neill1, Alison Matthews1, William B. Sherwin2
1NSW National Parks and Wildlife Service, PO Box 1967, Hurstville NSW 2220, Australia
2School of Biological Sciences, University of New South Wales, NSW 2052, Australia
This study investigated the recent demise of a koala population at Iluka in eastern Australia and demonstrates the potential role of population viability analysis (PVA) in the recovery and management of similar small populations. Information about the Iluka population was reconstructed from various sources, including community knowledge, wildlife carer data, and from a radiotracking program. Modelling scenarios were constructed to identify which factors may be critical to the survival of the Iluka population and which management options could provide the most effective means of its recovery. The model suggested that even substantial improvements in mortality and fertility alone do not prevent the modelled population declining towards extinction. Rebuilding of the koala population is likely to require guaranteed regular immigration of animals of both sexes in conjunction with considerable improvements in population mortality and fertility. This highlights the importance of the metapopulation for recruitment, an outcome that was not expected prior to modelling. These modelling outcomes suggest that the management of small, local populations of koalas will need a concerted management effort focusing on multiple causes of population change. Local management actions, such as reducing road deaths and managing habitat and fire, must be accompanied by knowledge of the larger geographical population.