Tree hollow requirements of leadbeater’s possum and other possums and gliders in timber production ash forests of the victorian central highlands

This study models relationships between the density of tree-hollow dependent possums and gliders and the density of potential nest trees (PNT), in timber production ash forests of the Victorian Central Highlands, where PNT are defined as all living or dead trees with≥0-5 m diameter at breast height and ≥6m height. The total density of all possums and gliders was found to increase linearly with PNT density, in an approximately 1: 1 ratio, then to plateau at an average maximum density of 11-3 animals per 3 ha once PNT density exceeded 12 per 3 ha. Regression models predict that Leadbeater’s possum will be absent from the majority of sites with fewer than 4 • 2 PNT per 3 ha and will increase linearly in density to an average maximum of 7 • 8 animals per 3 ha (or 3 • 1 colonies per 3 ha) on sites with more than 10 PNT per 3 ha. The absence of Leadbeater’s possums from sites with fewer than 4-2 PNT per 3 ha was attributed to; competition for hollows by other species; use of more than one PNT by individual colonies; and unsuitability of hollows in up to two out of every three PNT. Regression models predict that current logging prescriptions in ash forests, that call for retention of a minimum of 15 trees for every 10 ha clearfelled, will result in elimination of Leadbeater’s possum from the majority of clearfelled coupes, and will reduce the total number of hollow-dependent possums and gliders to less than one-eighth of their average maximum density in unlogged forest. The current decline in the availability of tree hollows caused by logging, fire and natural decay, is considered to be the most significant threat to the present and future survival of Leadbeater’s possum. A range of forest management options are presented and discussed to ensure the continued availability of PNT for hollow- dependent arboreal mammals in timber production forests.