Silently observing a darkened world from its lofty perch in the canopy of a eucalypt tree, the greater glider is the least vocal and most majestic of eastern Australia’s gliding possums. Only the soft rustling of leaves or bright white eyeshine reflected in the beam of a spotlight gives these shy creatures away. As their names suggest, they are the largest gliding marsupial in the world, reaching almost two kilograms in weight and with an impressive tail that can extend over half a metre.
Greater gliders have huge fluffy ears and impossibly long bushy tails. They vary in colour from a pale white morph to a dark brown/grey, with a spectrum of intermediate colour forms. Some individuals may have white flecks on their ears and around their nose. Their distinct colouration, small home ranges and preferences for particular trees are useful for identifying individuals in the field. Home ranges can be as small as one hectare where resources are plentiful, but may be as large as ten hectares in low productivity western areas. Territories are marked by secretions of their cloacal gland.
Like the koala, greater gliders feed on the leaves of species of Eucalyptus or Corymbia. Across their broad range in eastern Australia, many tree species are eaten, but local populations tend to feed on only two to three species. The largest trees in each area are typically preferred, as these old trees produce regular flushes of young leaf growth. Unlike their smaller gliding cousins, whose frenetic activity is fuelled by regular doses of nectar, pollen and sap, the low nutrient diet of the greater glider leads to a slow and languid lifestyle, more befitting their regal status.
Land clearing and fragmentation are two of the greatest threats facing greater gliders. The bushfires of 2019/20 placed additional pressure on populations already in decline, with around a third of all greater glider habitat in eastern Australia affected by the fires. As a result, they are now listed as endangered under both Queensland and national legislation. The greatest threat posed by vegetation destruction is the loss of hollow-bearing trees. As many as 20 different hollows may be used within a home range, and three to six hollow-bearing trees per hectare are required to meet their needs. Forest patches of at least 160 hectares are needed to support viable populations, and while the species is known to exist in urban patches much smaller than this, these small populations may be doomed to a slow extinction.
Their low rates of reproduction and their limited dispersal ability inhibits population recovery. While they can glide for distances of 100 m, they rarely come to the ground, so gaps larger than 100 m are an insurmountable barrier to movement. Greater gliders are also notoriously fussy when it comes to using nest boxes, but rear entry designs and moulded plastic hollows that mimic the thermal properties of natural tree hollows offer hope for the future. Friends of Nerang National Park have recently installed a mixture of 50 of these two designs, hoping to secure and expand the population of gliders in this 1600 hectare urban protected area. Actions such as these may provide a glimmer of optimism for the survival of these beautiful marsupials in the face of urban sprawl, continued land clearing, and increased risk of severe bushfires or prolonged heat waves in a changing climate.