Because of logging of its habitat and naturally occurring wildfire destruction, G. leadbeateri faces a grim future. Timber harvesting of the ash-type forests has, in recent years, been the major form of habitat destruction in Victoria. This process entails the removal of the large trees and then the subsequent burning and reseeding of the harvested site (Lindenmayer, 2000). Although these sites are eventually reseeded, the delicate nesting site is lost for many years. Wildfires have not been uncommon in highland Victoria, and these natural events have seriously plagued G. leadbeateri over the last 500 years (Lindenmayer and Taylor, 1995). One fire in 1939, in particular, burned nearly 70% of the region, in effect, decimating the Eucalypt tree populations on which Leadbeater's depends on for survival (Lindenmayer and Taylor, 1995).
A hollow or dead tree takes time to form. Estimates indicate that the largest Eucalypt trees require 150 years before can develop suitable nesting sites. With this long regeneration time complemented by the rapid destruction of the few remaining nesting sites, extinction of the species is perhaps inevitable and could conceivably occur in our lifetime (Lindenmayer and Taylor, 1995).
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: endangered
Young Leadbeater's Possums are very susceptible to attacks by owls. Like most marsupials, the young are protected by being kept in the mother's pouch for three months after they are born (Smith, 1995).
Known Predators:
Leadbeater's Possum is very similar in size and structure to the other sugar glider marsupials in the family Petauridae. It is typically gray-brown with a distinct dark stripe running the length of the back. The color on the underside is pale compared to the darker dorsal side. As typical of other Australian possums, a pouch used to harbor the live young is inconspicuous on the underside of the animal. Upon reaching maturity, Leadbeater's Possum has an average mass of about 135 grams. Although the average length is 300 mm upon reaching maturity, nearly half of this length is accounted for by a long tail (Lindenmayer and Taylor, 1995).
Leadbeater's Possum is the only member of its family without a gliding membrane, a fact that leads researchers to believe that G. leadbeateri is a primitive member of the group (Smith, 1984).
Range mass: 100 to 170 g.
Average length: 300 mm.
Other Physical Features: endothermic ; bilateral symmetry
Average basal metabolic rate: 0.574 W.
Average lifespan
Sex: male
Status: wild: 7.5 years.
Average lifespan
Sex: female
Status: captivity: 9.0 years.
Leadbeater's Possum lives in the highlands of Victoria between altitudes of 500 and 1500 meters (Massicot, 2001). The climate is cool and harsh and receives copious amounts of precipitation, some of which falls as snow during the winter. High annual precipitation amounts combine with cool temperatures to produce an open forest characterized by diverse species of tall, straight Eucalypt trees (Lindenmayer and Taylor, 1995). In particular, Leadbeater's Possum prefers to nest in the Mountain Ash. The steep terrain found in the highlands limits population size, as it has been estimated that only 6.7% of the forest is suitable nesting habitat (Massicot, 2001).
An important characteristic of the trees in which Leadbeater's nests in is that they must be dead or hollow. Typically, these "nesting trees" take over a hundred years to become suitable environments for the possum (Lindenmayer and Taylor, 1995).
Range elevation: 500 to 1500 m.
Habitat Regions: temperate
Terrestrial Biomes: forest ; mountains
Gymnobelideus leadbeateri, or Leadbeater's Possum, is strictly confined to a remote region in Victoria, Australia. It inhabits a range of only about 3500 square kilometers in the highlands of Victoria. Leadbeater's Possum is one of the most isolated marsupials in the wild (Massicot, 2001).
Biogeographic Regions: australian (Native )
The diet of G. leadbeateri consists of two main staples, both of which come from the plants and trees in the environment. Near the nesting site, many species of insects (beetles and crickets) and spiders can be found behind the bark of the three species of Eucalypt trees. Arthropods also can be obtained and utilized in the decaying logs and leaves that characterize the forest floor. Other important resources used by Leadbeater's are the exudates and saps that are produced by plants and some insects in the region. In fact, some estimates show that 80% of the daily energy intake comes directly from these sources (Smith, 1995).
Living in a temperate environment, food abundance varies seasonally. Typically, food is abundant in spring and summer, especially insects and plants, and all of the possum's energy requirements are usually met. During winter months, Leadbeater's has been observed eating a species of cricket that shelters itself by living behind the bark of the Mountain-Ash tree. This ability to find protein in the absence of many other food requirements may be what allows G. leadbeateri to reproduce in nearly all months of the year (Smith, 1995).
Animal Foods: insects; terrestrial non-insect arthropods
Plant Foods: sap or other plant fluids
Primary Diet: carnivore (Insectivore , Eats non-insect arthropods)
Leadbeater's Possum inhabits dead and decaying trees, many of which are filled with abundant insect populations. As a primary predator of tree-dwelling insects, the possum limits the insect influence in the ecosystem (Smith, 1995).
Perception Channels: tactile ; chemical
The gliding membrane, not found in G. leadbeateri, was perhaps a positive structural adaptation made by other members of Petauridae during the Pleistocene. The effects of this adaptation can be seen in the sugar glider Petaurus breviceps, which has flourished in modern times contrary to G. leadbeateri, which has been decimated (Massicot, 2000).
Leadbeater's Possum is monogamous, and young of both sexes are almost always displaced from the nest prior to reaching full maturity (Massicot, 2001).
Mating System: monogamous
Similar to most marsupials in Australia, G. leadbeateri has a very short gestation period. In fact, never has a gestation period ever been observed to be longer than 20 days (Smith, 1984). The young are born extremely altricial, and they are quickly placed into the pouch for protection and milk.
An interesting characteristic of Leadbeater's Possum is that it is polyoestrus; the loss of a litter stimulates the immediate production of another litter (Smith, 1984).
Although classified as a seasonal breeder, Leadbeater's Possums have been observed giving birth in every month except for January and February (Smith, 1984). The ability to breed in every winter month seems to be a direct indicator that the energy requirement necessary for pregnancy can be met even under restricted conditions (Smith, 1995).
Breeding season: April-June ; October-December
Range number of offspring: 1 to 2.
Range gestation period: 15 to 20 days.
Range weaning age: 10 to 15 months.
Average age at sexual or reproductive maturity (female): 2 years.
Average age at sexual or reproductive maturity (male): 2 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual
Average number of offspring: 1.5.
Average age at sexual or reproductive maturity (male)
Sex: male: 464 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 475 days.
Immediately after being born, young Leadbeater's Possums are transferred to the mother's pouch. Here, the poorly developed young stay an average of 85 days. At about three months, the defenseless young venture out of the nest for the first time to forage (Smith, 1995). Weaning takes place between 10 to 15 months after being born, with females leaving earlier than males. Leadbeater's Possum is fully mature by age two (Massicot, 2001). Because young are extremely altricial, mothers cover most aspects of parental care in their pouches. Here, the mother can provide the rich milk needed for rapid development as well as protection from outside dangers.
Parental Investment: altricial
Leadbeater's possum (Gymnobelideus leadbeateri) is a critically endangered possum largely restricted to small pockets of alpine ash, mountain ash, and snow gum forests in the Central Highlands of Victoria,[3] Australia, north-east of Melbourne.[4] It is primitive, relict, and non-gliding, and, as the only species in the petaurid genus Gymnobelideus, represents an ancestral form. Formerly, Leadbeater's possums were moderately common within the very small areas they inhabited; their requirement for year-round food supplies and tree-holes to take refuge in during the day restricts them to mixed-age wet sclerophyll forest with a dense mid-story of Acacia. The species was named in 1867 after John Leadbeater, the then taxidermist at the Museum Victoria.[5] They also go by the common name of fairy possum.[6] On 2 March 1971, the State of Victoria made the Leadbeater's possum its faunal emblem.[7][8]
Leadbeater's possum is thought to have evolved about 20 million years ago.[9] It was not discovered until 1867 and was originally known only through five specimens, the last one collected in 1909.[10][11] From that time on, the fear that it might be extinct gradually grew into near-certainty after the swamps and wetlands in Australia around Bass River in south-west Gippsland were drained for farming in the early 1900s.[12]
By the time of the 1939 Black Friday fires, the species was thought to have been extinct.[8][13] Then, on 3 April 1961, a member of the species was rediscovered by naturalist Eric Wilkinson in the forests near Cambarville, and the first specimen in more than 50 years was captured later in the month.[13][14][10]
In 1961, a colony was discovered near Marysville.[15] Extensive searches since then have found the existing population in the highlands. However, the availability of suitable habitat is critical: forest must be neither too old nor too young, with conservation efforts for Leadbeater's possum involving protection of remaining old-growth stands, and maintenance of younger stands that are allowed to attain hollow-bearing age.[4]
The combination of 40-year-old regrowth (for food) and large dead trees left still standing after the fires (for shelter and nesting) allowed the Leadbeater's possum population to expand to an estimated peak of about 7500 in the early 1980s.[16] From its peak in the 1980s, the Leadbeater's possum population was expected to further decline rapidly, by as much as 90%,[2] due to a habitat bottleneck. The population has dropped sharply since 1996.[12] Particularly, the February 2009 Black Saturday bushfires destroyed 43% of Leadbeater's possums' habitat in the Central Highlands, halving the wild population to 1,500.[8] A study in 2014 concluded there is a 92% chance the Leadbeater's ecosystem in the Victoria central highlands will collapse within 50 years.[17]
Leadbeater's possums are rarely seen as they are nocturnal, fast-moving, and occupy the upper storey of some of the tallest forest trees in the world.[2] They have an average body length of 33 cm (13 inches) with the tail included.[18] They live in small family colonies of up to 12 individuals,[11] including one monogamous breeding pair. Mating occurs only once a year, with a maximum of two joeys being born to each pair.[18] All members sleep together in a nest made out of shredded bark in a tree hollow, anywhere from 6 to 30 metres above ground level and roughly in the centre of a territory of 3 hectares, which they defend actively. The society of Leadbeater's possums is matriarchal: each group is dominated by only one female Leadbeater's possum that is active in expelling outsiders.[11] Other juvenile females are weaned off before they reach sexual maturity.[19] In addition, female Leadbeater's possums are more aggressive in nature, often engaging in frequent fights with other females, including their own daughters. Due to the constant attacks, young females are forced to leave much earlier than their male brothers, which results in the extremely high male to female ratio of 3:1.[19]
Solitary Leadbeater's possums have difficulty surviving: when young males disperse at about 15 months of age, they tend either to join another colony as a supernumerary member, or to gather together into bachelor groups while they wait to find a mate.
At dusk, Leadbeater's possums emerge from the nest and spread out to forage in the sub-canopy, often making substantial leaps from tree to tree (they require continuous understory to travel). Their diet is omnivorous: feeding on a range of wattle saps and exudates, lerps, and a high proportion of arthropods which they find under the loose bark of eucalypts, including spiders, crickets, termites and beetles. Plant exudates make up 80% of their energy intake, but the protein provided by the arthropods is essential for successful breeding.[16]
Births are usually timed for the beginning of winter (May and June) or late spring (October and November). Most litters are of one or two young, which stay in the pouch for 80 to 90 days, and first emerge from the nest following this. Young, newly independent Leadbeater's possums are very vulnerable to owls.
As of 2013, Leadbeater's possums are found in three habitat types: lowland swamp gum, of Yellingbo Nature Conservation Reserve; montane ash forest, wet sclerophyll forest dominated by mountain ash, shining gum and alpine ash with a dense mid-story of acacia species; sub-alpine woodlands of Mount Baw Baw, Lake Mountain and Mount Bullfight.
Leadbeater's possums and their forest habitat have been the subject of the largest longitudinal study of any species in the world—conducted by David Lindenmayer, a professor at the Australian National University, and his research assistants since 1983. Hundreds of peer reviewed scientific papers, journal articles and books have resulted from the years of data collection by the ANU team. Their findings show that the availability of suitable habitat is critical: forest must be neither too old nor too young, with conservation efforts for Leadbeater's possums involving protection of remaining old-growth stands, and maintenance of younger stands that are allowed to attain hollow-bearing age.[4] Clearfell logging and salvage logging (after bushfires) have been proven by the researchers to have been the greatest threat to the possums' conservation in the wild over the last three decades of the 20th century.
The entire Central Highlands population distribution is confined to a 70 by 80 kilometre area. With 43% of its known Central Highlands habitat[20] destroyed in the bushfires of February 2009 – large areas of forest around Toolangi, Marysville, Narbethong, Cambarville and Healesville – the species' status is currently in doubt.[21] Consequently, in December 2012, David Lindenmayer and Zoos Victoria's threatened species biologist, Dan Harley, submitted an application to the federal government for a revision of the species status, providing evidence that it should be relisted as critically endangered. The then minister for the environment, Tony Burke, agreed with the nomination and forwarded the application to the scientific committee of the EPBC Act requesting urgent consideration. On 22 April 2015, it was decided to relist the species as critically endangered.[22]
The only remaining population outside the Central Highlands is located at Yellingbo Nature Conservation Reserve. Harley has estimated this population to be fewer than 50.[23]
As the species is endangered and occupies a restricted range,[24] logging continues to pose a critical threat to the Leadbeater's possum. The logging in 1993 of "much of the possum's habitat, known as zone one" a five hectare reserve east of Powelltown, followed a "mapping error".[25] Author Peter Preuss stated that the possum's population faltered in 1997 with current habitat (limited to a 50-square-kilometre area) under threat from logging. He emphasised the need to relaunch a breeding program.[26]
Despite a joint federal and state government plan to save it, since the 1980s, the Leadbeater's possum population halved to around 2000 even before the Black Saturday fires. Many more were killed early in 2007 when the government-backed enterprise company, VicForests, bulldozed large firebreaks through Leadbeater's monitoring stations following the Christmas fires – firebreaks and clear-felling also prevent breeding with nearby colonies.[12]
David Lindenmayer (Australian National University) has argued that the need for nest boxes indicates that logging practices are not ecologically sustainable for conserving hollow-dependent species like the Leadbeater's possum.[27] Studies have shown that clear-felling operations, such as the logging run in state forest between the Yarra Ranges National Park and Mount Bullfight Conservation Reserve in February 2006, led to the deaths of most possums in the area—"Adult animals have a strong affinity with their home range and are reluctant to move".[28]
Salvage logging since the fires has posed a further risk to this extremely diminished population[29] with clear-felling also approved by VicForests in the few remaining unburnt areas, such as the Kalatha Creek area of Toolangi State Forest in 2010, a move opposed by the Yarra Ranges Shire Council.[30][31]
In 2012 MyEnvironment challenged VicForests' operations in three planned coupes in the Toolangi forest in the supreme court. The basis of their claim being that "VicForests did not undertake adequate pre-logging surveys prior to logging in an area that we claim meets Leadbeater's habitat and therefore should not have been logged."[32] The proposed logging is to supply (taxpayer subsidised) pulp to manufacture 'Reflex' copy paper—a product of Australian Paper owned by the Japanese company, Nippon Paper Group.[33] During the case, film was recorded of a Leadbeater's possum in the contested coupe area. The case was lost by MyEnvironment due to inconsistencies in the wording of the Leadbeater's Possum Action Statement (10 years out of date) and the forestry prescriptions adhered to by VicForests. The group immediately appealed the decision by the presiding judge Justice Osborne, and the supreme court accepted there was a sound basis for an appeal to the original determination. A supreme court appeal was heard on 24 June 2013 before three judges and MyEnvironment was represented in court by Julian Burnside QC. The appeal was lost.
Previously feral cats had only been considered a peripheral threat to Leadbeater's possums, but recent research has found video evidence of cats preying on possums leaving nesting boxes, and of possum remains in stomach contents of trapped feral cats. It is now considered that cats may be a more significant threat to possum populations, particularly in areas already disturbed by logging or bushfires.[34]
On 27 June 2013 the Napthine led State government passed legislative changes to allow VicForests access to Victoria's forests for the next 25 years and to be self monitoring (this follows the success of other recent cases preventing logging of remaining possum habitat). According to The Wilderness Society, "the Victorian government ... [is] virtually signing the death warrant of the remaining 500 or so Leadbeater's possums."[35] These changes to the Sustainable Forests (Timber) Act 2004 will have implications not only for the Leadbeater's possum but to the biodiversity, carbon storage and water catchments of the forests.[36][37]
On 22 April 2015, Greg Hunt, the Minister for the Environment, announced that the Leadbeater's possum would be listed as a "critically endangered" species under the EPBC Act.[22]
The forestry industry and Barnaby Joyce advocate for the Leadbeater's possum to be taken off the critically endangered list.[38] Following uproar from the logging industry & the National Party it was soon placed under re-assessment. On the eve of an ABC 4 Corner episode on "Extinction" (24 June 2019) the then Environment Minister, Sussan Ley announced that it would be re-listed as "critically endangered".
Of its ash forest habitat, about 30% is protected, while the rest is allocated to logging.
In addition there is a small isolated, genetically distinct, population protected within the Yellingbo Nature Conservation Reserve.[2] This lowland habitat consist primarily of Sedge-rich Eucalyptus camphora Swamp.
In 2013 it was proposed to create the "Great Forest National Park" to protect the mountain ash forest habitat.[39] The park would protect the area between Kinglake, Baw Baw and Eildon national parks, which is also important for Melbourne's drinking water and as a carbon sink.[40]
Since 2004, the Friends of Leadbeater's Possum community group has been active in raising the animal's profile and lobbying for its conservation.
Through a joint community/government program, "Project Possum" has installed approximately 200 plastic nest boxes in the wild. Many of these nest boxes were paid for by a community fundraising campaign. The nest boxes are primarily used to assist with ongoing population monitoring and supplement the declining forest habitat. Project Possum has targeted two forest types: montane ash forest (i.e. Mt Ritchie, Dowey Spur, Ben Cairn) and sub-alpine woodland (i.e. Mount Baw Baw, Lake Mountain, and Mount Bullfight). The nest boxes are routinely checked for habitation every one or two years. Nest boxes located in the sub-alpine woodland tend to have a high uptake, while those located in montane ash forest have very limited uptake. An additional 50 nest boxes are due for installation in 2015–16.
Des Hackett is credited as the first person to successfully breed the Leadbeater's possum in captivity. In May 2006, the last Australian specimen at the time, held at Healesville Sanctuary, died. In January 2010, Kasia, at the time the last captive Leadbeater's possum worldwide, died at Toronto Zoo.[41] The predation in early 2012 by a feral cat of the few Lake Mountain Leadbeater's possums remaining after the 2009 bushfire led to three remaining individuals being taken into captivity for their own protection.[42] One animal has since died.[43] There are no plans to release the remaining two animals despite a further two colonies of Leadbeater's possums having recently been located at Lake Mountain in remnant gully vegetation. These two Lake Mountain animals are now on public display in the Nocturnal House as ambassadors for the species. Healesville Sanctuary's captive breeding program for Leadbeater's possums recommenced in May 2012 and now comprises 6 individuals from the genetically distinct Yellingbo population. As of May 2015, they are housed as pairs in large enclosures off display, but are yet to breed.
On 14 September 2017, National Geographic reported that the Leadbeater's possum was the 7,000th animal photographed for The Photo Ark by Joel Sartore.[44] The project's goal is to photographing all species living in zoos and wildlife sanctuaries around the globe in order to inspire action to save wildlife.[45]
Leadbeater's possum (Gymnobelideus leadbeateri) is a critically endangered possum largely restricted to small pockets of alpine ash, mountain ash, and snow gum forests in the Central Highlands of Victoria, Australia, north-east of Melbourne. It is primitive, relict, and non-gliding, and, as the only species in the petaurid genus Gymnobelideus, represents an ancestral form. Formerly, Leadbeater's possums were moderately common within the very small areas they inhabited; their requirement for year-round food supplies and tree-holes to take refuge in during the day restricts them to mixed-age wet sclerophyll forest with a dense mid-story of Acacia. The species was named in 1867 after John Leadbeater, the then taxidermist at the Museum Victoria. They also go by the common name of fairy possum. On 2 March 1971, the State of Victoria made the Leadbeater's possum its faunal emblem.
