In 1939, massive wildfires tore through much of Victoria, including the majority of the Central Highlands. At the time, Leadbeater’s Possum was thought to be extinct, with the last recorded animal seen in 1909 in NE Victoria. Then in 1961, 22 years after the fires, it was rediscovered in the forests above Marysville, near Tommys Bend. Since then, the possum has become one of Victoria’s faunal emblems, and the focus of much conservation research.
For over thirty years, Australian National University researchers have undertaken stagwatching for Leadbeater’s Possum and other fauna at 175 permanent monitoring sites. Following the Black Saturday fires, Leadbeater’s Possum had not been recorded on any site which was burnt, until now.
Seven years ago, in February 2009, wildfires again ravaged the Central Highlands, however this time, intensive research had been underway for 25 years by the Australian National University. Following the 2009 fires, we surveyed all of our 175 long term monitoring sites and did not find Leadbeater’s Possums on any site that had been burnt, even by low severity fire.
We knew from areas burnt by the 1939 and 1983 fires that Leadbeater’s Possum eventually returns after fire, provided large old trees are present within that regrowth. However, one of the key unknown questions relating to Leadbeater’s Possum was how long after the fires would it be until the possum began returning to burnt areas?
In January 2016, after seven years of surveying for Leadbeater’s Possum in burnt forests around the Central Highlands without success, that question was finally answered. With suitable synchronicity, this ‘new rediscovery’ was also at Tommys Bend.
“The survey had been fairly uneventful, a clear night with barely a puff of wind. A Mountain Brushtail Possum emerged from the one remaining stag tree that persisted after the fires and lumbered off through the forest. I heard a bit of scratching on the ground, possibly an antechinus or native Bush Rat and that appeared to be it. I was about to pack away my binoculars and pull out my torch, when I heard a familiar rustle. A small creature was making its way from tree to tree, through the 10m high regrowth canopies. As the noise got closer, I started to pick up eye shine with my night vision binoculars. Still closer it came, until a small possum with a club shaped tail was sitting, clinging to a thin trunk only 4m away – a Leadbeater’s Possum! It sat there checking me out – a strange visitor to its forest - for well over 10 minutes, sometimes changing the angle of view with small agile leaps from one trunk to another. Being so close, and knowing the importance of this moment, I snapped a couple of photos using my phone – not the best photos, but good enough to confirm what I had seen.”
- Dave Blair
One of the photos I took with my phone at the end of the stagwatch. The possum was only a few metres away from me, but its defining club shaped tail is clearly visible. Photo: Dave Blair.
The possum travelled into our site from beyond the back boundary. It was using the young regrowth on our site as part of its foraging range, but it had not denned there. Prior to the fires, this site had five possible possum den trees, now due to the fires, it has just one. Unfortunately, these old trees are in decline right across the landscape, as are the possums that use them.
The Ash forests of the central highlands of Victoria are covered with complex layers of fire history. This map shows that although the majority of the area around the monitoring site was severely burnt in the 2009 Black Saturday fires, there are areas of older forest and lower severity burns close to the monitoring site.
Why is this finding important?
After hundreds of nights surveying since the 2009 fires (including by other institutions and government bodies), this is the first record of a Leadbeater’s Possum on a burnt site. This discovery fills an important knowledge gap of what the earliest stage is when Leadbeater’s Possum might begin to reuse young forest regrowing from fire.
But it’s just one observation and does not mean all seven year old regrowth is suitable habitat, shown by all our other burnt research sites surveyed this year which did not have Leadbeater’s Possums present. Indeed there are many forest areas that have regrown after fire that have remained unsuitable for the possum for over 70 years.
Following the 2009 fires, many of the large hollow bearing trees either collapsed as this one has done, or were totally burnt out up the middle. Either way, they are no longer functional denning sites for any of the possums or gliders.
The fact we found Leadbeater’s Possum on this particular site is no coincidence. To understand why, we need to look at the habitat elements of the surrounding landscape that 30 years of research has taught us are critical for Leadbeater’s Possum to persist.
The forest behind our site (the direction the possum came from) has many large old trees that had been protected from logging over the years by the Leadbeater’s Possum reserve system. During the fire in 2009, this area of older forest burned at lower severity than much of the surrounding younger forest and as a result, some of the large old trees survived while others died but remain standing as large dead stag trees. Less than a kilometer from this patch was a large patch of green forest – unburnt by the fires because it was a wet rainforest gully, again with old eucalypts. It is likely the possum I saw (or its parents) had survived the fire in that refuge.
When is young regrowth suitable for Leadbeater’s Possum?
Can you spot the Leadbeater’s Possum ‘keyhole’ hollow entrance? Leadbeater’s Possums prefer large dead trees for their den sites. Typically, they enlarge cracks in the side of the trunk, accessing the rotten middle of the tree which maintains moderate temperatures through the hot summers and the cold winters.
The limiting habitat requirement for Leadbeater’s Possum in mountain ash forest is hollow bearing trees. Post-fire regrowth forest can be suitable for the species when there are old trees (usually 120+ years old) within the forest that burns. However, without these ‘keystone’ habitat structures, the forest is very unlikely to support Leadbeater’s Possum. Unfortunately, the availability of such trees has declined rapidly over the last 20+ years, and continues to do so, leaving most young regrowth as unsuitable habitat.
Only 1% of the Central Highlands ash forests are now in an old growth stage. Unlike the 1939 fire which burnt many large old trees across the landscape leaving high densities of suitable dead habitat trees, most of the forest now is too young to provide similar denning resources should another fire occur soon.
It is always exciting making new discoveries, and it pays off years of hard work doing hundreds of surveys. While it is great to know Leadbeater’s Possums have survived in this area, the struggle to create areas of old growth trees that will sustain the species into the long term future continues. At the very least, this record shows every old tree is precious and their presence in this landscape is vital to the survival of the Leadbeater’s Possum.
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