The conservation of arboreal marsupials in the montane ash forests of the Central Highlands of Victoria, south-east Australia: II. The loss of trees with hollows and its implications for the conservation of leadbeater's possum Gymnobelideus leadbeateri McCoy (marsupialia: petauridae)

Leadbeater's possum, Gymnobelideus leadbeateri McCoy, a rare and endangered arboreal marsupial inhabiting the montane ash forests of the Central Highlands of Victoria, is dependent on hollows in mature and dead trees. The number of trees with hollows that had collapsed between 1983 and 1988 was assessed at 32 sites located in ash-type forests in the Central Highlands of Victoria, south-eastern Australia. The extent of decay amongst standing trees with hollows was also determined. A simple stochastic model of the decline and collapse of these trees was calculated from the data. The model was applied to data on trees with hollows collected from 497 other sites within the study region to predict their future abundance and availability over the next 75 years. Almost 18% of the total measured population of trees had collapsed in the 5-year interval between assessments. A subjective categorization of the form of the trees was the best predictor of the susceptibility to collapse. More senescent trees were those most vulnerable to collapse and they also exhibited the highest rates of decay. Stochastic models based on transition probabilities of trees with hollows predict that very few of the sites surveyed will support such trees in 50 years time and imply a severe future shortage of trees containing suitable nest hollows for wildlife until at least the end of the next century. Silvicultural practices which result in ash-type forests being clear-felled on a short-term (80-120 year) rotation will further accelerate and exacerbate the anticipated shortage. The implications of these effects for wildlife, particularly G. leadbeateri, are discussed.