|Scientific Name:||Gymnobelideus leadbeateri McCoy, 1867|
|Red List Category & Criteria:||Critically Endangered A2abc+3bc+4abc ver 3.1|
|Assessor(s):||Woinarski, J. & Burbidge, A.A.|
|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:|
|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.
|Range Map:||Click here to open the map viewer and explore range.|
During the past decade, and especially because of wildfire in 2009, severe declines have occurred in all forest types that the possum inhabits.
|Current Population Trend:||Decreasing|
|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).
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Generation Length (years):||6|
|Movement patterns:||Not a Migrant|
|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).|
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 22 February 2018.|
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