Animal Info - Leadbeater's Possum

Gymnobelideus leadbeateri

Status: Endangered


Contents

1. Profile (Picture)
2. Tidbits
3. Status and Trends (IUCN Status, Countries Where Currently Found, Population Estimates, History of Distribution, Threats and Reasons for Decline)
4. Data on Biology and Ecology (Weight, Habitat, Age to Maturity, Birth Season, Birth Rate, Early Development, Dispersal, Diet, Social Organization, Age and Gender Distribution, Mortality and Survival, Density and Range, Minimum Viable Population)
5. References


Profile

Pictures: Leadbeater's Possum #1 (16 Kb JPEG) (Unique Austral. Anim.); Leadbeater's Possum #2 (30 Kb JPEG) (Unique Austral. Anim.); Leadbeater's Possum #3 (73 Kb JPEG) (Mus. Vict.); Leadbeater's Possum #4 (97 Kb JPEG) (Terrambiente)

Leadbeater's possum is a small marsupial weighing 120 - 160 g (4.3 - 5.8 oz). It is arboreal and nocturnal, and constructs a nest of loosely matted bark in a hollow tree. Leadbeater's possum requires a forest containing large living or dead mountain ash trees with hollows in which to nest and an understory containing wattle acacia which supplies gum to supplement its main diet of insects. Its society is based on a matriarchal system. Individual females occupy large nests in hollow trees and actively defend a surrounding territory from other unrelated females. The family group may contain several generations of offspring as well as unrelated males. Mating is monogamous and male partners assist females in defense of territories against unrelated females.

Leadbeater's possum probably had a wide former range in the state of Victoria, Australia, but it was rare by the time it was discovered by Western science in 1867. Until recently, it was regarded as extinct, after disastrous fires throughout its range in 1939. However, in 1961 a small colony was rediscovered near Marysville, Victoria. As of 1996 it was confined to an area of about 3500 sq km (1350 sq mi) near the western limit of Victoria's Central Highlands.

Climate and flora changes since the Pleistocene led to competition with the glider Petaurus breviceps and the glider appears to have been more successful than Leadbeater's possum. The main concern for the species' survival now are habitat fragmentation and the decline of suitable hollow-bearing trees due to natural attrition, fire and the activities of timber harvesting.


Tidbits

*** Leadbeater's possum is the official animal of Victoria State, Australia.

*** By cutting notches in the bark of a tree with its teeth, it causes the tree to exude gum, which it eats.

*** The mountain ash tree required by Leadbeater's possum is the world's tallest hardwood (up to 100 m (330')) and is Australia's most valued timber producing tree.

*** The fact that it is the adult female, and not the male, that shows the most aggression socially is uncharacteristic of mammals.


Status and Trends

IUCN Status:

  • 1960's: Insufficiently Known
  • 1970's - 1994: Endangered
  • 1996 - 2004: Endangered (Criteria: A2c, E) (Population Trend: Decreasing) (IUCN 2004)

Countries Where Leadbeater's Possum Is Currently Found:

2004: Occurs in Australia (Victoria). (IUCN 2004)

Population Estimates:

[Note: Figures given are for wild populations only.]

History of Distribution:

Leadbeater's possum probably had a wide former range in the state of Victoria, Australia, but it was rare by the time it was discovered by Western science in 1867. Its previous range also included areas south and northeast of its present distribution. In addition, fossils from New South Wales have been discovered. Until recently, it was regarded as extinct, after disastrous fires throughout its range in 1939. However, in 1961 a small colony was rediscovered in the Cumberland Valley area near Marysville, Victoria. By 1990 it had been found at more than 50 localities scattered over 1000 sq km (385 sq mi) of forest from Mt. Torbreck to Mt. Baw Baw in southeast Victoria.

As of 1996 it was confined to an area of about 3500 sq km (1350 sq mi) near the western limit of Victoria's Central Highlands, including the upper reaches of the La Trobe, Thomson, Bunyip, Yarra and Goulburn River systems at altitudes between 500 and 1500 m (1600 - 4900').  There is also a small, isolated population near Yellingbo. (Maxwell et al. 1996)

Distribution Map #1 (4 Kb GIF) (Maxwell et al. 1996)
Distribution Map #2 (7 Kb JPEG) (Unique Austral. Anim.)

Threats and Reasons for Decline:

Climate and flora changes since the Pleistocene led to competition with the glider Petaurus breviceps and the glider appears to have been more successful than Leadbeater's possum. The main concern for the species' survival now are habitat fragmentation and the decline of suitable hollow-bearing trees due to natural attrition, fire and the activities of timber harvesting.


Data on Biology and Ecology

Weight:

Leadbeater's possum weighs 120 - 160 g (4.3 - 5.8 oz).

Habitat:

Moist tall open forest dominated by montane ash (mountain ash, alpine ash, shining gum) containing large living or dead mountain ash with hollows in which to nest and an understory containing silver or mountain hickory wattle acacia which supplies gum to supplement the Leadbeater's possum's main diet of invertebrates. The central highlands of Victoria contain approximately 1700 sq km (660 sq mi) of montane ash forest, although suitable habitat within this area is generally uncommon and is predicted to constitute only 6.7% of this area (114 sq km/44 sq mi).

Age to Maturity:

2 years.

Birth Season:

Leadbeater's possum appears to breed in all months except January and February. The most common birth months are May, June, October and November.

Birth Rate:

Litters of 1-2 are common.

Values of parameters that were input to population viability modeling (Lindenmayer & Possingham 1996):

Annual probability of 0 female young per female: 0.45
Annual probability of 1 female young per female: 0.30
Annual probability of 2 female young per female: 0.18
Annual probability of 3 female young per female: 0.06
Annual probability of 4 female young per female: 0.01

Early Development:

Young are weaned at about 3 months.

Dispersal:

Adult females enforce the dispersal of their offspring when they are approximately 12 months old (10 months for female young; 15 months for male young).

Diet:

The Leadbeater's possum's diet consists mainly of insects that live on foliage and under bark, supplemented by plant exudates and sweet secretions produced by sap-sucking insects.

Social Organization:

The Leadbeater's possum's society is based on a matriarchal mating system where individual females occupy nests in large hollow mountain ash trees and actively defend a surrounding 1 - 3 hectare (2.5 - 7.5 acre) exclusive territory from other females. Mating is strictly monogamous and male partners assist females in defense of territories. Additional adult males, as well as one or more generations of offspring, may be tolerated in family groups by the breeding pairs. However, additional adult females are not tolerated, and an associated higher female mortality results in a high male:female ratio. The fact that it is the adult female, and not the males, that show most aggression socially is uncharacteristic of most mammals. The members of the colony engage in mutual grooming and seem to recognize each other by smell.

Age and Gender Distribution:

The male:female ratio is 3:1.

Mortality and Survival:

Values of parameters that were input to population viability modeling (Lindenmayer & Possingham 1996):

Annual probability of death:

Newborn: 0.0
Juvenile: 0.3
Adult: 0.3

Density and Range:

Within its distribution, Leadbeater's possum is usually found in a density of 1.5 - 3 individuals/hectare (0.6 - 1.2 individuals/acre). (Flannery 1990) Females defend an exclusive territory of 1 - 3 hectares (2.5 - 7.5 acres). Surveys have shown approximately one reproductively active female per 6 hectares (15 acres) of old-growth forest. (Lindenmayer & Possingham 1996)

Values of parameters that were input to population viability modeling (Lindenmayer & Possingham 1996):

Minimum home range size of females in highest quality habitat: 1 hectare (2.5 acres)
Minimum home range size of breeding females in old growth: 3.3 hectares (8.3 acres)
Maximum population density of females: 2 individuals/hectare (5 individuals/acre)

Minimum Viable Population:

Minimum Viable Population Density: 300 individuals/sq km (780 individuals/sq mi). (Silva & Downing 1994)


References

Burbidge & McKenzie 1989, Burton & Pearson 1987, Clark et al. 1991, Curry-Lindahl 1972, Flannery 1990, IUCN 1966, IUCN 1994, IUCN 1996, IUCN 2000, IUCN 2003a, IUCN 2004, Kennedy 1992, Lindenmayer et al. 1993, Lindenmayer & Possingham 1996, Maxwell et al. 1996, Mus. Vict., Nowak & Paradiso 1983, Oryx 1991, Terrambiente, Unique Austral. Anim.


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Last modified: January 5, 2005;

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