Pale-coloured Southern Greater Glider on one of the study transects in May 2023

A recent survey in the Greater Blue Mountains has found significantly increased populations and good post-fire recovery of the Southern Greater Glider in the vicinity of Wombeyan Karst Conservation Reserve. With the 2019-2020 Black Summer bushfires resulting in an estimated 60% decline in the species in the region, these results are encouraging.

The survey provides key insights into the post-fire recovery of gliders and other arboreal mammals impacted by the bushfires and the extreme drought and heatwaves of 2019 that led to the fires.

In Autumn, as part of an annual post-fire monitoring program, ecologists Dr Peter Smith and Dr Judy Smith were engaged by Kanangra-Boyd to Wyangala (K2W) Link Inc to survey the Wombeyan and Jenolan Karst Conservation Reserves to assess the post-fire recovery of tree-dwelling mammals. Funding for the repeat survey was provided by the Great Eastern Ranges and WWF-Australia as part of a broader bushfire recovery effort in the state.

As part of the monitoring, the ecologists counted gliders along seven 500 metre transects through tall eucalypt forests using spotlights to detect the animals. The counts were repeated over three nights per transect.

Plateau forests support threatened species

The Smiths have recorded seven species of arboreal mammals on these transects over the years, including three threatened species (Southern Greater Glider, Yellow-bellied Glider and Spotted-tailed Quoll) and four non-threatened species (Feathertail Glider, Krefft’s Glider, Common Brushtail Possum and Common Ringtail Possum). All except the Common Ringtail Possum have been found again since the fires.

“The survival and recovery of Southern Greater Gliders in the less badly burnt forests has been much better than expected and is very encouraging. They have been able to survive in sites where there was at least some live eucalypt foliage for them to feed on in the immediate aftermath of the fires. They have recovered rapidly because of the good rainfall and plant growth in the years since the fires,” the Smiths said.

“The tall forests in the eastern parts of the K2W Link support unusually high numbers of Southern Greater Gliders and are a critically important refuge for the species in this region.”

These tall, moist, fertile, seldom-burnt plateau forests in and around the south-western corner of the Greater Blue Mountains World Heritage Area are a favoured habitat of the Southern Greater Glider. They have provided an important refuge for Southern Greater Gliders during and after the extreme drought and fires of 2019-2020 and served as a climate change refuge before 2019 for this heat-sensitive species, which has been retreating from warmer, lower elevations in the Blue Mountains since the 1990s.

“The first post-fire breeding season in 2020 was unsuccessful,” the Smiths said. “However, there was an increase in the Southern Greater Glider population following the 2021 breeding season and there has now been a further increase following the 2022 breeding season.”

Recovery of the Southern Greater Glider following the Black Summer bushfires at Wombeyan and Jenolan

Trends in the sightings of Southern Greater Gliders

The increase has been greatest in the transects that were unburnt or only lightly burnt, which are also the tallest forests and best glider habitat sampled, supporting higher glider densities than the other transects. The numbers of Southern Greater Gliders recorded on these transects in Autumn 2023 were 89% higher than the first post-fire counts in 2020 and 64% higher than the numbers recorded in pre-fire, pre-drought surveys in 2016. This is attributed to the remarkable increase in the wet La Nina conditions since the fires, which have promoted abundant regrowth of soft young eucalypt foliage for the gliders to feed on.

Southern Greater Gliders have also increased on the moderately burnt transects, but not to the same extent. In Autumn 2023, the numbers were 63% higher than the first post-fire counts in 2020 and 26% higher than in pre-fire, pre-drought counts in 2016-18.

However, the ecologists found no sign of recovery in the severely burnt transects, where Southern Greater Gliders are thought to have been eliminated by the fires and have not reappeared since.

“The severely burnt transects are a different story and the species is likely to be absent from these transects for years to come, as seen in Sydney’s Royal National Park following the 1994 bushfires, where Southern Greater Gliders were wiped out and did not recolonise until 18 years later.

“The lack of recovery in severely burnt forests is worrying,” the Smiths said.

The Smiths warn that “survival of the species in the long term will depend on whether the Black Summer fires were an exceptional event that will not recur for many decades or whether they are the start of a permanent change in the fire regime to more frequent, more extensive, more severe wildfires as a result of climate change.

“Such a drastic change in the fire regime would have catastrophic effects on many fauna and flora species.”