The greater gliders are three species of large gliding marsupials in the genus Petauroides, all of which are found in eastern Australia. Until 2020 they were considered to be one species, Petauroides volans. In 2020 morphological and genetic differences, obtained using diversity arrays technology, showed there were three species subsumed under this one name. The two new species were named Petauroides armillatus and Petauroides minor.
These species are not closely related to the Petaurus group of gliding marsupials but instead to the lemur-like ringtail possum, Hemibelideus lemuroides, with which it shares the subfamily Hemibelideinae.
The greater gliders are nocturnal and are solitary herbivores feeding almost exclusively on Eucalyptus leaves and buds. Like their relative, the lemur-like ringtail, the southern greater glider is found in two forms: a sooty brown form and a grey-to-white form. The central greater glider is instead silvery brown, while the northern greater glider is brownish-gray.
The greater gliders are found in eucalypt forests from Mossman, Queensland, to Daylesford, Victoria.
Taxonomy
Although the genus was formerly thought to be monotypic, there are now known to be three species in the genus:
Central greater glider (Petauroides armillatus) Northern greater glider (Petauroides minor) Southern greater glider (Petauroides volans)
The species are known to hybridize with one another near the edges of their ranges.
Anatomy and physiology
The three species differ in their size, with the northern greater glider only growing to the size of a small ringtail possum, while the southern greater glider grows to the size of a house cat. The central greater glider is intermediate between these two.
Greater gliders have a head and body long, with the females generally being larger than the males. Their body is covered with a shaggy coat of fur that increases their apparent size, and the tail is long and bushy, ranging from . The head is short with a pointed muzzle and their large ears are fringed and backed with long fur.
Each side of the body bears membranes stretching between the elbow and the ankle that give these animals the ability to perform controlled glides. This is in contrast to other gliding marsupials, such as the sugar glider, that have gliding membranes stretching from the wrists to the ankles.
The feet have strongly recurved claws to grip onto bark or other surfaces. There are five toes on each foot. The first toe on the hind foot and the first two toes on the fore foot are opposable.
The fur is soft and up to long. All three species have cream undersides and primarily differ in the coloration of their pelages. The northern greater glider has a brownish-gray coloration, the central greater glider has a dark silvery-brown coloration with dark brown face, legs, and tail, while the southern greater glider varies between a dark, almost black morph or a pale white and gray morph. Body mass varies from in the southern greater glider of Victoria to in the northern greater glider of north Queensland.
Physiology
Heat management in the greater gliders is performed by licking extremities and the ventral body surface, and direct evaporation is the main method of cooling. They can also use their gliding membranes to reduce heat loss by increasing the layer of insulation at the skin surface. The gliders are not well equipped to handle high ambient temperatures as they inefficiently use water for evaporation via salivation despite arboreal habitats often having limited water accessibility.
These gliders can digest low nutrient foliage, specifically eucalypt leaf matter, which contains a variety of phenolic and terpenoid compounds and a high concentration of lignified fibre. These animals can digest about 50–60% of the leaf during its passage through the gut. Their guts have a specialized caecum that contains a population of bacteria that ferment food residues that remain undigested in the small intestine. For a population in a eucalypt forest near Maryborough, Queensland, it has been calculated that their daily energy intake is about 1130 kJ, which is provided by about of dry matter daily.
Mature females will give birth to a single joey each year which is typically born in late autumn or early winter. The underdeveloped offspring will then spend the next four months within the pouch of the mother to suckle and develop, and will remain within the security of the pouch until nine months of age.