Predictions of the impacts of changes in population size and environmental variability on Leadbeater's possum, Gymnobelideus leadbeateri McCoy (Marsupialia: Petauridae) using population viability analysis: an application of the computer program VORTEX

Population Viability Analysis (PVA) uses computer modelling to simulate interacting deterministic and stochastic factors that act on small populations and assess their long-term vulnerability to extinction. The computer program VORTEX was used in a PVA of Leadbeater's possum, an endangered arboreal marsupial that is restricted to the montane ash forests of the central highlands of Victoria. An annual linear decline in the carrying capacity in all or parts of the habitat will lead to the extinction of G. leadbeateri in those areas. There is presently a decline in suitable habitat because of an annual loss of more than 3.5% of trees with hollows, which provide nest sites. The species could be lost from large areas within the next 50 years. PVA was also used to determine the viability of populations in areas, such as old-growth forest, where there is not likely to be a steady decline in habitat carrying capacity resulting from the loss of trees with hollows. This allowed an analysis of the cumulative impacts of small population size, environmental variation and genetic factors, which showed that, for a 100-yr projection, simulated populations of 200 animals or more remained demographically stable and experienced a less than 10% decline in predicted genetic variability. -from Authors