With so many weird and wonderful marsupials to hog the limelight, Australia's greater gliders have been largely overlooked, to the point we have only now learned there are three species, not one. However, this makes one of them even more endangered than previously thought.
Tree-dwelling animals learned the advantages of gliding to escape predators or reach food as far back as the Jurassic. Quite distinct families of mammals have evolved skin flaps to extend their range, but Dr Kara Youngentob of the Australian National University told IFLScience this can obscure their major differences.
Greater gliders inhabit an immense area of Australia that also extends to the wet tropics. Consequently, even after losing much of their habitat to last summer's bushfires, they are only classified as threatened. However, marsupial expert Stephen Jackson long ago noted differences in the size, fur color, and energy expenditure of gliders by region, and suspected they actually represented three species, with each being far more restricted and therefore vulnerable.
Youngentob is part of a team that has confirmed Jackson's theory by testing the genomes of gliders from Victoria to North Queensland. In Scientific Reports, they give the existing name Petauroides volans to the southern greater glider, now quite likely very endangered after so much of its territory burned. The names P. minor and P. armillatus have been given to two Queensland species.
"There has been speculation for a while that there was more than one species of greater glider, but now we have proof from the DNA. It changes the whole way we think about them,” said James Cook University PhD student Denise McGregor in a statement.
Petauroides minor (top left), P. armillatus (bottom left) P. volans (right). Even to the uninitiated, some of the differences between the species are visible. Steven Kuiter
Greater gliders feed exclusively on eucalyptus leaves. Although normally abundant, these are very low in energy, causing koala's famous sleepiness. Youngentob said greater gliders are similarly lethargic. Although sometimes thought of as larger cousins of the equally adorable sugar gliders, Youngentob told IFLScience each evolved gliding independently. Sugar gliders' high-energy diet make them “intense little forest gremlins”, and Youngentob said she has “literally seen them running laps” around greater gliders.
Indeed, all three greater glider species are so reluctant to waste energy that Youngentob said they are sometimes captured for study by shooting out the branch they are sitting on, at which point they glide to the ground. “Sometimes it takes a few shots, which are really loud,” Youngentob said, “And they're just sitting there and looking at you as if to say, 'What are you doing?'”
Variation in their extraordinary tails was one of the features that alerted Jackson to the species divisions. Youngentob told IFLScience their tails are not used to grip branches but to act as a counterweight while sitting and as a rudder while gliding. In the mating season, gliders frequently like to sit together with their tails wrapped around each other, a fact that might go some way towards achieving Youngentob's goal of building public pressure to save them. “They've played second fiddle to koalas for too long,” she said.
