Thought to be extinct after disastrous fires in 1939, Leadbeater’s possum (Gymnobelideus leadbeateri) was only rediscovered in 1961 in Marysville near Melbourne, Australia (6). Similar to other marsupial gliders, the Leadbeater’s possum has a long bushy tail, large ears and eyes, and thick soft fur (4). It is grey-brown with a dark stripe running the length of the back, and a paler underside (3). There are dark patches at the base of the ears, as well as above and below the eyes (4). It is thought to be a more primitive member of the glider group as it has no gliding membrane (3). This marsupial has an inconspicuous pouch (5).
Unusually for mammals, Leadbeater’s possum has a female-dominated society. Pairs are monogamous, but the female vigorously defends her 0.01 – 0.03 km² territory against other mature females, including her own daughters (5). Within each territory a single nest is made of loosely matted bark inside a hollow mountain ash tree (6). The nest can contain up to eight individuals, consisting of the reproducing pair, their offspring and unrelated sexually mature males. Nest mates share in mutual grooming and recognise one another through smell (6). The dominant female mates throughout the year giving birth in any month except January and February (5) to one or two offspring (6). Pregnancy lasts no longer than 20 days, and following birth, the underdeveloped offspring crawl to the pouch for protection and milk. They remain there for 85 days until developed enough to venture out of the nest to forage. Weaning takes place at 10 months for female offspring and 15 months for male offspring. Full maturity is reached at around age two, but many females will not survive to this age as they are not welcome in the home ranges of other mature females. Males out-number females three-to-one as a result (5).
This nocturnalmarsupial has a fairly sedentary lifestyle. It eats insects and spiders from behind the bark of three species of eucalyptus (5), as well as cutting notches into the bark of Acacia with its teeth causing the tree to release gum, which it eats (6). As Leadbeater’s possum lives in a temperate area, food availability is seasonal and the diet is cricket-based during the winter (5). The young may be preyed upon by owls (5), but survivors can live to at least 7.5 years (2).
Found only in Australia, Leadbeater’s possum has a limited distribution of about 3,500 km² near the western end of Victoria’s Central Highland at altitudes of between 500 and 1,500 m above sea level. A small isolated population has also been found near Yellingbo, east of Melbourne, Victoria (1).
This species has very specific habitat requirements as it needs regenerating or uneven-aged ash forests that contain both eucalypt species and old hollow mountain ash trees. It does not thrive in old ash forests (1).
Leadbeater’s possum is heavily dependent on old mountain ash trees for nesting sites, and these trees are threatened by timber operations and wildfire (1). Deforestation is followed by burning and reseeding, but these young trees will not make suitable nest sites for another 150 years (5).
Already endangered, this species cannot fully recover for 50 – 100 years as the old trees that are crucial to its lifestyle are currently too young. Populations in sub-optimum older-aged and mixed-aged forest are less dense than populations in optimal habitat, but older forests are thought to be less at risk from wildfires (3). Therefore, a management plan is in place that involves protecting both optimum and sub-optimum habitat with a nature reserve system as well as an alternative logging system that preserves high quality habitat (3). Experiments with the introduction of nest boxes have been partially successful, with 13 out of 96 nest boxes now occupied by Leadbeater’s possum (7).
A diverse group of mammals characterised by their reproduction. The embryo is born 11-35 days after conception. The tiny newborn crawls into the marsupium (pouch) and attaches to a teat where it stays for a variable amount of time. They also differ from placental mammals in their dentition.
Michael, D.R., Rawlins, D., Crane, M., Incoll, R.D., Cunningham, R.B., MacGregor, C.I. and Lindenmayer, D.B. (2003) The use of nest boxes by arboreal marsupials in the forests of the Central Highlands of Victoria. Wildlife Research, 30(3): 259 - 264.
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