Populations of large hollow-bearing trees, including those typically selected for occupancy by arboreal marsupials, are in rapid decline in mountain ash forests. This decline, coupled with the prolonged period until current cohorts of existing younger trees eventually reach an age (and therefore diameter) that are suitable for occupancy by arboreal marsupials, underscores the critical need to protect all existing hollow-bearing trees from practices that can otherwise destroy them, including industrial clearfelling operations. Better protection is important not only in the small remaining areas of old growth. Mountain Ash forest but also in regrowth forest where such trees are scarce and have high marginal value as nesting sites, as reflected by high rates of per tree occupancy rates in stands of this age