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).
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).
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).
Leadbeater's Possum is monogamous, and young of both sexes are almost always displaced from the nest prior to reaching full maturity (Massicot, 2001).
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).
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.
G. leadbeateri lives a nocturnal, sedentary life. Usually, groups of around 4-8 individuals inhabit a given nest. This group is consists of a monogamous pair of mature adults and their offspring. Typically, the group maintains a defended territory ranging from 2.5 to 7.5 acres in area. With his strict investment and attachment to one female, the male helps in defending the territory (Massicot, 2001).
Atypical of most mammal social hierarchies, Leadbeater's Possum societies are dominated by a female. In each group, only one adult female is present, and juvenile females are weaned well before they reach maturity. Observations of two adult females living in the same nest usually reflect an unstable group characterized by frequent fighting (Smith, 1984). Another interesting feature of this female-based society is that females are the aggressors, often engaging in displays of violence against other females and even their own daughters. As a result, young females leave the nest at a much younger age compared to the young males, which are tolerated to sometimes stay indefinitely (Smith, 1995). A direct consequence of this type of society is the extremely high male to female ratio of 3:1 (Massicot, 2001).
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).
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).
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).
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).
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).
Rodgers Eckhart (author), University of Michigan-Ann Arbor, Ondrej Podlaha (editor), University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly insects or spiders.
Having one mate at a time.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
Lindenmayer, D. 2000. Factors at multiple scales affecting distribution patterns and their implications for animal conservation-Leadbeater's Possum as a case study. Biodiversity and Conservation, 9: 15-35.
Lindenmayer, D., M. Taylor. 1995. "The Leadbeater's Possum Page" (On-line). Accessed October 6, 2001 at http://incres.anu.edu.au/possum/possum.html.
Massicot, P. 2001. "Animal Info - Leadbeater's Possum" (On-line). Accessed October 2, 2001 at http://www.animalinfo.org/species/gymnlead.htm.
Smith, A. 1995. Leadbeater's Possum. Pp. 224-226 in R Strahan, ed. Mammals of Australia. Washington D.C.: Smithsonian Institution Press.
Smith, A. 1984. Demographic Consequences of Reproduction, Dispersal and Social Interaction in a Population of Leadbeater's Possum. Pp. 359-373 in A Smith, I Hume, eds. Possums and Gliders. Australia: Surrey Beatty & Sons Pty Limited.