Habitat segregation, competition and selective deforestation: effects on the conservation status of two similarPetaurusgliders

Two very similar arboreal marsupials occur in subtropical eastern Australia: the sugar glider Petaurus breviceps, and the squirrel glider P. norfolcensis. Both are dependent on forest and do not occur once tree cover has been removed. Maps of the pre-European and recent extent of rainforest in south east Queensland were compiled from a range of sources and compared with past (1820-1974) and recent (1975-1996) site records of the two glider species, also drawn from a range of sources. P. breviceps occurred commonly in rainforest and related vegetation types in both historical and recent times, while P. norfolcensis occurred mainly in drier forest types. Interspecific competition is a likely cause of these broad habitat differences between the two glider species, with squirrel gliders being competitively superior, but exhibiting a narrower range of preferred habitats. Rainforest has been cleared from large areas, especially in the lowlands, and this would have reduced sugar glider numbers. However, the species is still present in small rainforest patches, such as riparian strips within drier lowland forests, and appears secure in upland rainforest reserves. The squirrel glider, a nationally more threatened species, would have been less affected by historical deforestation but now faces contemporary clearing of lowland eucalypt associations. It may experience a rapid decline within the urbanising south-east Queensland lowlands unless substantially more remnant vegetation is protected than seems likely under current vegetation management legislation.