DNA in droppings adds acacia and casuarina to the endangered greater glider's diet

Greater gliders feed at night in the tree canopy ^[10]. Until this study, working out their diet meant sorting plant fragments by eye from stomach contents or droppings, or noting which trees the animals were seen feeding in ^[8]. "The methods used previously weren't particularly accurate," said Dominique Potvin, an associate professor at the University of the Sunshine Coast and an author of the paper ^[9][11]. Sequencing the plant DNA in droppings identifies species without anyone having to recognise a chewed leaf. It also needs no sighting of the animal. The team did not have to build an assay from scratch. It used a recently developed genetic tool originally designed for koalas ^[6].

The 17 species come from 24 samples ^[4][5]. That figure is a tally of everything detected across the whole set. The phys.org account does not say how many samples contained each plant, or how many individual gliders the 24 came from. A plant found once, in one dropping, counts toward the 17 the same way a eucalypt found in every sample would.

The comparison is with earlier records. Greater gliders have generally been thought to feed only on eucalyptus foliage, and the sequencing added acacia, casuarina, angophora and corymbia species ^[1]. "Some of the plant types we found in their diet had never been documented before and were quite unexpected," Potvin said ^[2]. She stated the main result plainly: "Foremost, greater gliders are not quite the fussy eaters we thought and are open to a wider variety of nutritional sources" ^[3].

On habitat, Potvin said the findings "could potentially change vegetation strategies" ^[14]. "The information we've gathered will allow us to recommend what trees need to be prioritized in glider habitats, a vital part of saving a species in decline," she said ^[13]. I think the result is enough to add these genera to the trees surveyed in glider habitat now. It does not yet show that habitat chosen around eucalyptus leaves out something gliders need. DNA in a dropping shows that a plant was swallowed. It does not show how much was eaten, whether the mouthful was deliberate, or whether a glider would do worse without that plant.

Potvin also raised geography. "Another thing we found was that gliders from different areas might be eating different things, which warrants further investigation," she said ^[12]. If that holds, a single food-tree list for the region would fit some local populations poorly. The 24 samples were drawn from across southeast Queensland ^[4], so each area contributes only a fraction of them.