Gymnobelideus leadbeateri 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Diprotodontia Petauridae

Scientific Name: Gymnobelideus leadbeateri McCoy, 1867
Common Name(s):
English Leadbeater's Possum

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2abc+3bc+4abc ver 3.1
Year Published: 2016
Date Assessed: 2014-04-22
Assessor(s): Woinarski, J. & Burbidge, A.A.
Reviewer(s): Hawkins, C.
Contributor(s): Menkhorst, P., Harley, D., Lindenmayer, D. & Taylor, A.

Leadbeater’s Possum has a small population size that is declining rapidly because of reduction in habitat suitability (especially availability of suitable hollows), mostly due to fire and ongoing timber harvesting. It has a limited distribution and exists as a series of small, severely fragmented subpopulations. Significant declines in population size have occurred during the past decade in all forest types inhabited by the Leadbeater’s Possum. Of the available high quality habitat, 40-45% was burnt in the 2009 Black Saturday fires (D. Lindenmayer, D. Harley pers. comm. in Woinarski et al. 2014). Post-fire monitoring has shown that it is now absent from sites burnt in 2009, irrespective of burn severity, indicating that the population size has declined by >40% since 2009. Monitoring of known subpopulations and modelling indicates that the current rate of decline is >50% and suspected to be >80% over the last 18 years (= three generations), with this rate likely to increase over the next 18 years. This species is therefore listed as Critically Endangered.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Leadbeater’s Possum is endemic to Australia, where it is restricted to central Victoria. Most of its limited range is in the forests of the central highlands, bounded by Toolangi (in the west), Beenak (in the south), Mt Baw Baw (in the east) and Rubicon (in the north), in an elevational range from about 500 to 1,500 m a.s.l. (Harley 2004). An isolated subpopulation occurs at lower altitudes (c. 110 m a.s.l.) at Yellingbo, 16 km south-west of its main range (Harley et al. 2005; Hanson and Taylor 2008). Menkhorst (2008) considered its extent of occurrence was <5,000 km2, and that ‘it has a limited distribution (<3500 km2)’. The total ‘range’ occupied by the species was estimated as 3,526 km2 by Department of Sustainability and Environment (2010).

Based on a small number of known historical records, its former range extended c. 120 km further to the north-east (Mt Wills), and more extensively to the south, from the Western Port region to the Yarra Valley, with this latter (lowland) subpopulation (now represented only at Yellingbo) evolutionarily distinct from the more extensive highland subpopulations (Harley 2004; Hansen and Taylor 2008). Bilney et al. (2010) reported bones of this species commonly in subfossil material (regurgitated pellets from Sooty Owls Tyto tenebricosa) in Gippsland, indicating it was more abundant and widespread prior to European settlement.

The extent of occurrence has changed little over the last three generations, but the number of occupied sites has declined dramatically following extensive wildfire in 2009.
Countries occurrence:
Australia (Victoria)
Additional data:
Estimated area of occupancy (AOO) - km2:284-5000,3500Continuing decline in area of occupancy (AOO):Yes
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:1938-20000,10000
Continuing decline in extent of occurrence (EOO):YesExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:2-20,5Continuing decline in number of locations:Yes
Extreme fluctuations in the number of locations:NoLower elevation limit (metres):80
Upper elevation limit (metres):1500
Range Map:Click here to open the map viewer and explore range.

Population [top]


During the past decade, and especially because of wildfire in 2009, severe declines have occurred in all forest types that the possum inhabits.

The discrete subpopulation in the small Yellingbo area was estimated to contain 60 individuals in 2012 (Threatened Species Scientific Committee 2015). The total population size across the main range of Leadbeater’s Possum is less well resolved. Threatened Species Scientific Committee (2015) noted a range of estimates from 2000 to 11,250, and concluded that the number of mature breeding individuals was less than 10,000 and very likely to be less than 2500. The 2009 Black Saturday fire burnt 45% of high quality Leadbeater’s Possum habitat (D. Harley pers. comm. in Woinarski et al. (2014)). Post-fire surveys indicate that the species is absent from burnt sites, regardless of burn severity (D. Lindenmayer pers. comm. in Woinarski et al. (2014); P. Menkhorst pers. comm. in Woinarski et al. (2014)). Thus, the population size is likely to have been reduced by at least 45% since 2009. The severe impacts of the 2009 fire are highlighted by results from Lake Mountain, where a major subpopulation stronghold containing 200-300 individuals was reduced to just six individuals (i.e. >95% mortality) (D. Harley pers. comm.). The 2009 fires also reduced the availability of suitable tree hollows, particularly dead standing trees preferred by Leadbeater’s Possum.

Even prior to the 2009 fires, modelling predicted that subpopulations in montane ash forest would decline by about 90% over the 30 year period from 2008 due to loss of suitable den trees (Lindenmayer et al. 1990, 1997, 2012; Smith and Lindenmayer 1992; Menkhorst 2008).

Monitoring indicates that the Yellingbo subpopulation declined from 122 individuals in 2003 (D. Harley pers. comm. in Woinarski et al. (2014)) to just 60 individuals in 2012, representing a 46% decline over nine years (D. Harley pers. comm. in Woinarski et al. (2014)). There has been a 30% reduction in the occupied area of the reserve over this period, and it is estimated that less than 20 ha of high quality habitat is currently available (D. Harley pers. comm. in Woinarski et al. (2014)). Further declines are anticipated due to ongoing deterioration in habitat condition. Fire poses a major risk to this small, localized subpopulation.

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:1100-11000, 2500Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:10Continuing decline in subpopulations:Yes
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:

Leadbeater's Possum is a nocturnal, arboreal species that spends its day in tree hollows. Its diet mainly consists of exudates from trees and to a lesser extent arthropods (Smith 1984).

Optimum habitat for Leadbeater's Possum is a regenerating or uneven-aged Ash forest with a dense understorey of Acacia trees and an ample supply of old hollow trees. The species’ occurrence and population size is strongly linked to nest hollow availability (e.g. Lindenmayer et al. 1991, 2013).

Leadbeater’s Possums do not occur on burned sites until required conditions have returned (Lindenmayer et al. pers. comm., 2014a in Threatened Species Scientific Committee 2015).

The occurrence and quality of habitat is primarily determined by patterns of successional change and stand development resulting from disturbance, such as past wildfires and timber harvesting operations. Regrowth from the 1939 wildfires, combined with fire-killed remnants of mature forest, has provided abundant feeding and nesting habitat during the last 30 years.

Older aged and mixed aged forest containing live hollow-bearing trees also support populations of Leadbeater's Possum, although not in the same high densities that can be found in suitable regrowth forests. The role, however, of these suboptimal forests in the medium-term will be critical for conservation of the species. These forests are not subject to a rapid decline in habitat suitability that is predicted to occur in current high value habitat regrowth forests. Older aged forest and mixed aged forest with hollow-bearing trees and a low occurrence of wattles are defined as potentially optimum habitat because of their potential to become optimum in the short term (<30 years), as a result of natural or deliberate disturbance.

In surveys to identify current strongholds after the 2009 fires, sites most likely to be occupied by Leadbeater’s Possum were generally characterised by lush, unburnt vegetation in gullies in areas that had relatively low summer temperatures and high summer rainfall (Lumsden et al. 2013).

Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):6
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): This species is heavily dependent on old trees, and fire-killed remnants that are rapidly decaying and falling over. Recruitment of suitable hollows, used for shelter and breeding, is very slow. The long-term viability of habitat in mature and mixed aged forests is threatened by wildfires and some timber harvesting practices. The species and its remnant habitat also are closely tied to a narrow set of climatic conditions that could be severely affected by global warming (Lindenmayer et al. 1991).

Conservation Actions [top]

Conservation Actions: The Leadbeater's Possum occurs in a number of protected areas (including a 30,500 ha fragmented Leadbeater's Possum permanent reserve system) and is listed as a threatened species both nationally and within Victoria. A recovery plan for the species was prepared (Macfarlane et al. 1997), as well as several conservation strategies (e.g., Smith 1982; Smith et al. 1985; Macfarlane and Seebeck 1991; Lindenmayer et al. 1991; Lindenmayer and Possingham 1994). A Victorian government Action Statement, which described key management responses, was established and implemented in 2014 (Department of Environment and Primary Industries 2014). A national recovery plan is scheduled to be developed and implemented in 2016. Populations of this species have been monitored over the last several years conducted by numerous volunteers and public awareness of the plight of this species is high (Smith and Harley 2008). Research into the effects of fire and ways to improve timber harvesting techniques are important.

The species’ dependence on tree hollows that resulted from burnt remnant trees from the 1939 fires led to dire predictions about its population trend over the next 30 years as these trees continued to collapse, with similar concerns following the 2009 fires. The use of nest boxes as a management tool has received some attention as one way to possibly ameliorate the imminent cavity shortage. Research in the central highlands suggests that nest boxes receive a low rate of occupancy and would be ineffective as a large-scale solution to the problem (Lindenmayer et al. 2003). However, nest box occupancy rates are much higher at Yellingbo (Beyer and Goldingay 2006; Harley 2006). 

Population viability analysis by Lumsden et al. (2013) found that the current reserve system alone to be insufficient to ensure the long-term conservation of the species, resulting in recommendations for additional management actions such as protection of known colonies in state forest, protection of additional areas of suitable habitat, habitat enhancements and alternative silvicultural practices (Lumsden et al. 2013; Threatened Species Scientific Committee 2015). 

Large-scale clear-cutting and even-aged stand management is detrimental to the species, and there have been efforts to adopt harvest practices that are compatible with the conservation of the species. The preservation of more large trees with hollows and a dense habitat structure with an understorey of Acacias is essential (Smith and Lindenmayer 1992; Smith and Harley 2008). Recent management recommendations for timber harvesting have increasingly responded to some of the Leadbeater's Possum's needs. These include detailed recommendations for post fire timber salvage that protects patches of tall trees (Lindenmayer and Ough 2006), and maintenance of timber stands above threshold densities of large old trees.

The Threatened Species Scientific Committee (2015) concluded that the most effective way to prevent further decline and rebuild the population of Leadbeater’s Possum would be to cease timber harvesting within montane ash forests of the Central Highlands.

Citation: Woinarski, J. & Burbidge, A.A. 2016. Gymnobelideus leadbeateri. The IUCN Red List of Threatened Species 2016: e.T9564A21959976. . Downloaded on 23 September 2018.
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