A good possum is hard to find
Leadbeater’s Possum, Gymnobelideus leadbeateri
The story of Leadbeater's Possum is a remarkable one. The species was first described in 1867, but by the early 1900s it was thought to be extinct.
Miraculously it was rediscovered near Marysville in 1961 and became Victoria's state faunal emblem in 1971. Its current status is endangered under both Commonwealth and State legislation.
The possum is unique to Victoria and lives mainly in the Central Highlands. It's entire distribution is an area just 70 x 80 km. Almost half its habitat was burnt in the Black Saturday bushfires in 2009. As our climate changes and high intensity bushfires become more frequent, the Leadbeater's Possum will be at greater risk of extinction.
The possum's habitat also overlaps valuable timber production forests. The species' continued existence is dependent on careful management of these areas.
First found in Gippsland, Leadbeater’s Possum is now restricted to Mountain Ash or sub alpine woodland in Victoria’s Central Highlands. There is also a small population at Yellingbo, about 50 km east of Melbourne.
The average length of the possum is 32 cm, half of which is its distinctive club shaped tail with bushy tip. A dark (dorsal) stripe runs along it’s back. Adults weigh 100–170 g.
Leadbeater's Possum is a nocturnal marsupial which den in tree hollows and make an elaborate nest. They feed on plant saps, wattle gum, spiders and insects.
It lacks the gliding membranes of related species such as the Sugar Glider. The possums live in small family groups. Females are territorial and may produce two litters a year.
The major threat to Leadbeater's Possum at present is the lack of suitable forest habitat. In particular they require suitable tree hollows for nesting, and it takes a Mountain Ash (Eucalyptus regnans) – the tallest flowering plant on the planet – more than a century to develop hollows, and more than 200 years before they possess cavities suitable for a family of Leadbeater’s Possums to den in.
Such trees are in short supply due to past timber harvesting practices which has interrupted the replenishment of suitable hollows. The possum also requires dense middle storey of wattles for feeding and movement. Thus, the species has specific habitat requirements which render it vulnerable to habitat loss.
Our State Emblem under fire
In the past, wildfire has created and destroyed suitable habitat for Leadbeater's Possum.
The 1939 fires in the Central Highlands created valuable nesting environments. These fires killed centuryold mature trees, producing hollows in which the possum could nest. The presence of numerous 'stags' within the younger forest regenerating from the fires has created the ideal mixedaged forest structure for Leadbeater’s Possum.
However, the 2009 fires did not produce the same outcome as few trees were old enough to produce such 'stags'. Fires in younger forests stimulate the regeneration of dense habitat suitable for foraging possums, but also exacerbate the hollow shortages which threaten Leadbeater's Possum.
The Black Saturday Bushfires of February 2009 have had a severe impact on the availability of suitable habitat for the species. Fire in the Kilmore East Murrindindi complex, which burnt areas including Kinglake and Marysville, damaged 43 percent of the possum's known habitat, which was previously reserved for their protection.
The subalpine woodland on the Lake Mountain plateau, dominated by Snow Gum, is estimated to have supported between 100 and 300 Leadbeater's Possums prior to the Black Saturday fires. Prior to the February 2009 bushfire, Leadbeater's Possums had constructed large, dense nests of finely shredded bark in 28 of 30 boxes installed as survey tools by Parks Victoria and researchers.
The Black Saturday bushfires were particularly intense at Lake Mountain, severely burning 95% of the plateau. Following the fires, just two of the thirty nest boxes remained intact. Twentytwo were totally destroyed, and a further six were badly damaged. Many natural hollows were badly damaged or destroyed by the fires.
In the aftermath of the fires, Parks Victoria officers visited the location of each of the 30 nest boxes to determine the extent of damage and whether possums had survived. In one nest box, an entire, intact possum colony, containing a breeding pair and two offspring, were found to have survived. At two other localities, lone possums were found.
Parks Victoria and the Friends of Leadbeater's Possum have undertaken a number of steps to aid the recovery of the Leadbeater’s Possum population at Lake Mountain. All damaged and destroyed nest boxes have been replaced. New boxes have been installed at locations previously inhabited by colonies denning in natural hollows. Additional boxes have also been erected in the small patches of green unburnt habitat. In July 2009, this led to the discovery of a second colony of two Leadbeater’s Possums that survived the February fire.
A carefully rationed supplementary feeding program was established in June 2009. Supplementary feeding stations were established to assist the surviving possums through the winter months when food resources may be critically low. Friends of Leadbeater's Possum volunteers undertake twice weekly feed runs to support the handful or survivors.
Dan Harley, "Snow Possum: Project ALPS" in Wildlfe Australia Magazine, Winter 2007, p3235
David Lindenmayer, Wildlife and Woodchips, (University of New South Wales Press, 1996)