49.
Leadbeater's Possum
(Gymnobelideus leadbeateri)
EN
Overview
Leadbeater’s possum is a small arboreal marsupial that was not sighted for 50 years and believed to be extinct prior to its rediscovery in 1961. The possum is the only marsupial endemic to Victoria, and has been adopted as one of the state's two faunal emblems. The species’ entire distribution in the wild is restricted to a 70 x 80 km area. Populations are predicted to undergo substantial declines owing to a lack of mature trees with hollows that provide diurnal den sites for possum colonies. As a consequence, the species is listed as ‘Endangered’.
Urgent Conservation Actions
All areas of optimum and potentially optimum habitats need protection and a reserve system should be established across the species' range.
Distribution
Australia (Victoria).
Media from ARKive
ARKive video - Leadbeater's possum - overview
ARKive image - Leadbeater's possum
ARKive video - Leadbeater's possums feeding
ARKive image - Leadbeater's possum showing dark stripe along back
ARKive video - Leadbeater's possum moving through canopy
ARKive image - Leadbeater's possum on branch
ARKive image - Leadbeater's possum
ARKive video - Leadbeater's possums in nest hole
ARKive image - Pair of Leadbeater's possums climbing down tree trunk
ARKive image - Leadbeater's possum on trunk of tree
Evolutionary Distinctiveness
Order: Diprotodontia
Family: Petauridae
The family Petauridae is known from fossils dating back to the Micene (7-26 million years ago) in Australia. The family comprises 11 species: four striped possums (genus Dactylopsila) and seven wrist-winged gliders (Gymnobelideus and Petaurus). Leadbeater’s possum is thought to be a more primitive member of the glider group as it has no gliding membrane. It is the only living member of its genus.
Description
Size: 
Head and body length: 150-170 mm
Tail length: 150-180 mm
Weight: 110-165 g
Leadbeater’s possum is similar in appearance to the other marsupial gliders in the family Petauridae. Its short, dense fur is greyish brown above and paler below, with a distinctive dark stripe running along the centre of the back, from the forehead to the base of the tail. The species has dark markings around its large eyes and ears, and an inconspicuous pouch. It is distinguishable from the related sugar glider (Petaurus breviceps) by the absence of a gliding membrane and a club-shaped tail, broader near the tip than at the base. Leadbeater’s possum has enlarged (spatulate) toe pads with claws that area reduced in size relative to other members of the Family Petauridae.
Ecology
The species is nocturnal, arboreal and sedentary. Its diet comprises sugary plant and insect exudates, such as saps, gum and honeydew, which are a good source of carbohydrates. The possums feed on invertebrates for protein (e.g. spiders, tree crickets, beetles). The availability of tree crickets, which live beneath the bark of Mountain Ash eucalypts, throughout the colder winter months is thought to permit winter breeding.

Unlike most mammal species, the social structure of Leadbeater’s possum denning groups (colonies) is matriarchal (female dominated). Females defend a territory of 1-3 hectares from other mature females, including their own daughters. The species lives in colonies of 2-10 individuals, consisting of a monogamous breeding pair, their offspring and unrelated adult males. These groups spend the day huddled together within a nest of shredded bark that is constructed within tree hollows. Den trees may be living or dead. Breeding has been observed throughout the year. As with other marsupials, the gestation period is very short, lasting no longer than 20 days. The poorly developed offspring are immediately transferred to the pouch where they receive milk and protection for a further 85 days. Litter size is 1-2. Females are polyoestrous, which means that the loss of one litter immediately stimulates the production of another in the same breeding season. Females typically produce two litters per year. At one site, 35–40% of the young that leave their mothers’s pouch survive to an age where they may disperse (i.e. around 10 months), and approximately 20% survive to an age where they are likely to breed (i.e. > 2 years). Both sexes disperse. At one site in lowland swamp forest, average dispersal distances for males and females were 495 m and 407 m, respectively. Most individuals disperse from their natal territory prior to breeding. Sexual maturity is reached prior to 2 years, although few females breed until they are older than this (owing to limited opportunities within established colonies where there is only a single resident breeding female).. The maximum lifespan of the species in the wild is approximately 9 years.
Habitat
Found in three distinct forest types: tall, wet eucalypt forest dominated by Mountain Ash (Eucalyptus regnans), Alpine Ash (Eucalyptus delegatensis) or Shining Gum (Eucalyptus nitens) (400–1200 m asl); sub-alpine woodland dominated by Snow Gum (Eucalyptus pauciflora) (1400–1500 m asl); and lowland swamp forest dominated by Mountain Swamp Gum (Eucalyptus camphora) (110 m asl).The species needs nest sites in living or dead old-growth trees and forages on eucalypts and wattles. Key features of the possum’s preferred habitat include numerous tree hollows, smooth-barked eucalypts and dense vegetation structure.

Optimum habitat consists of regenerating or uneven-aged forest that contains younger trees for foraging and mature trees with hollows for nesting. Trees with hollows suitable for denning are more than 100 years old. A dense middlestorey or canopy is required for the animals to move through the forest, jumping from tree to tree. In favourable habitat, the distance between the den sites of neighbouring possum colonies is usually 100–200 m.
Distribution
Endemic to Australia, Leadbeater’s possum has a patchy distribution restricted to a 70 x 80 km area in the Victorian Central Highlands at altitudes of 400-1,500 m above sea level. There is also a small, isolated population inhabiting lowland swamp forest at Yellingbo, approximately 50 km east of Melbourne, Victoria.

Extinct in the lowland forest of south-west Gippsland and possibly montane areas of north-east Victoria.
Population Estimate

Following the 2009 bushfires in Victoria, Leadbeater's possum lost 42% of their habitat and estimates of their population in the wild is now under 1,000 individuals. The population numbers in the Yellingbo Reserve have dropped by 40% over the past 8 years and there is a possibility of them now being brought into captivity again for protection against a potential fire or other stochastic event. The last individual held in captivity died in 2006.

Population Trend

Decreasing.

Status
Classified as Endangered (EN B1ab(iii)) on the 2010 IUCN Red List of Threatened Species.
Threats

The species is at risk from habitat fragmentation and the decline of suitable tree hollows due to timber harvesting and naturally occurring wildfires. Timber harvesting entails the removal of large trees and the subsequent burning and reseeding of the harvested site. Regrowth from wildfires, such as the devastating 1939 ‘Black Friday’ fires, has provided abundant feeding and nesting habitat for the species during the past 40 years. However, the fire-killed hollow trees are now rapidly decaying and falling over, and the younger regenerating trees will not become suitable nest sites for another 150 years. Loss of nests sites has led to a decline in possum populations, and the fragmentation of areas of suitable habitat is leading to small non-viable populations.

 

The most recent threat to their survival now is the logging of their Central Highlands Mountain Ash habitat by VicForests, with the latest 2011 Timber Release Plan Amendments recently being released showing incredibly threatening logging in known Leadbeater's possum habitat and through areas being used for research by Australian National University.

Conservation Underway

Approximately one-third of the known distribution of the species comprises protected areas. Management strategies have been implemented to protect the current habitat and provide for the development of new habitat in the future. The strategies should ensure that timber production is managed more effectively in retaining sufficient hollow-bearing trees. A permanent reserve system for the species is being developed, although this process has experienced lengthy delays. Research has been conducted on the biology, ecology and habitat requirements of the species, which has enabled a Recovery Plan to be produced. Experiments with the provision of nest boxes have been extremely successful in some areas and disappointing in others.

 

It seems that to prevent extinction of this relatively rare creature involves the re-establishment and protection of native forests with enough old trees to support the possum’s habitat needs. The Friends of Leadbeater’s Possum undertake volunteer works with rangers in Victoria’s national and state forests to put up nestboxes in the possums’ habitat to provide homes if there is a shortage of hollows in old trees, and the public are being encouraged to 'adopt' one of these nest boxes. As of february 2011, over 190 Leadbeater’s Possum (LBP) nestboxes with 99 installed in LBP habitat and regularly monitored. They have placed nestboxes at the sites of the most severely damaged forests, such as Mount Bullfight and Lake Mountain, as well as undertaking yearly revegetation works at Yellingbo National Park.

Conservation Proposed

Habitat protection is the main management action required. The recovery plan recommends that all areas of optimum and potentially optimum habitats are protected and that a reserve system is established across the range of the species. The establishment of the latter has experienced lengthy delays and is yet to be finalised. Further research and monitoring of the species throughout its known range is also needed to ensure that the recovery programme is effective. The current Leadbeater’s Possum Recovery Plan is out of date and due for revision. The establishment of an active recovery team will be an important step in efforts to conserve the possums.

Links
References

Australasian Marsupial & Monotreme Specialist Group. 1996. Gymnobelideus leadbeateri. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. Downloaded on 09 August 2006.

Macfarlane, M., Lowe, K. and Smith, J. 1995. Flora and Fauna Guarantee Action Statement No. 62. Leadbeater’s Possum Gymnobelideus leadbeateri. Flora and Fauna Branch, Department of Conservation and Natural Resources, East Melbourne.

Macfarlane, M., Smith, J. and Lowe, K. 1997. Leadbeater’s Possum (Gymnobelideus leadbeateri) Recovery Plan. Department of Natural Resources and Environment Victoria: Australia.

Maxwell, S., Burbidge, A. A., Morris, K. and the IUCN/SSC Australasian Marsupial and Monotreme Specialist Group (eds.). 1996. The 1996 Action Plan for Australian Marsupials and Monotremes. Wildlife Australia, Endangered Species Programme.

Menkhorst, P. 2008. Gymnobelideus leadbeateri. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4.www.iucnredlist.org. Downloaded on 14 November 2010.

Menkhorst, P. 1996. Mammals of Victoria: Distribution, Ecology and Conservation. Oxford University Press, Melbourne.

Nowak, R.M. 1999. Walker's Mammals of the World. Sixth edition. The Johns Hopkins University Press, Baltimore and London.

Strahan, R. 1995. The Mammals of Australia. Reed Books, Sydney.

Distribution map based on data provided by the IUCN Global Mammal Assessment

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