Mahogany Glider
Mahogany glider
Petaurus gracilis
The mahogany glider is the second largest of six gliders occurring in Queensland. It is listed as Endangered under the Queensland Nature Conservation Act 1992 and the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.
The mahogany glider is nocturnal, elusive and silent for much of the time. It was described in 1883 from a skin by Charles de Vis, a noted naturalist and amateur geologist who became an early curator of the Queensland Museum. Little more was known about the mahogany glider for over a hundred years and doubts were raised at to whether it actually existed. However, some clever detective work by scientists resulted in the exciting rediscovery of the mahogany glider in 1989 at Barrett's Lagoon near Tully in north Queensland.
The mahogany glider. Photo: DERM
What do mahogany gliders look like?
The mahogany glider receives its name from its buff- coloured belly. The top of the head is pale and bears a dark stripe. Fully grown mahogany gliders are around 600mm long from head to tail-tip and weigh 300-450g.
The mahogany glider, in common with other gliders, has a fold of skin which stretches between the front and rear legs. This acts as a parachute enabling individuals to glide for distances averaging 30m and sometimes longer. The long tail is used for stabilisation especially when coming in to land on tree trunks.
Mahogany gliders are much larger than their closest relative, the squirrel glider, with which they may be confused in the wild
Where do mahogany gliders live?
Mahogany gliders are restricted to the coastal southern Wet Tropics region of northern Queensland. They live in a narrow and highly fragmented band of lowland sclerophyll forest extending around 140 km from Toomulla north of Townsville to Tully and up to 40km inland. Most recorded sightings have been at altitudes below 120m. The main canopy and sub-canopy trees are eucalypts, bloodwoods and paperbarks and less commonly swamp mahogany and turpentine with an open mid-stratum of smaller trees and shrubs (eg. wattles, forest siris, golden parrot tree, black she-oak, pandanus) and a grassy ground stratum in which grass trees may be present. The mahogany glider requires a relatively open forest structure for efficient gliding and tends to avoid dense vegetation such as rainforest.
Mahogany glider habitat. Photo: J. Kemp (DERM)
What does the mahogany glider eat?
The mahogany glider forages alone at night feeding on nectar, pollen and sap of over twenty different species of trees and shrubs. It also eats honeydew (a sweet sticky substance excreted by insects such as aphids), insects such as lerps and the arils of wattles (an aril is a protein-rich stringy structure which connect seeds to the pod). Nectar and pollen feeding gliders are known to provide an important ecosystem function as pollinators of tree species such as some eucalyptus and banksia.
How does the mahogany glider breed?
Mahogany gliders use hollows in large eucalypts and bloodwoods as dens for sleeping and rearing their young. They den either alone or in pairs and can use up to 10 dens in a single season. Dens are lined with a thick mat of leaves.
Mahogany gliders appear to be socially monogamous. Individuals may den with their mate and actively mark and defend their home ranges by chasing out other individuals. Territories are around 20ha in size.
Mahogany gliders first breed at around 12–18 months and wean their young after 4–5 months. They generally raise only one litter per breeding season. The average litter size is 1.55 young, usually born between April and October. After weaning, juveniles of both sexes appear to disperse from the parental home range.
What are the threats to the mahogany glider?
Fragmentation and isolation of populations and decline in habitat quality are major ongoing threats to the mahogany glider. Other causes of mortality include entanglement in barbed wire fencing, road kills and possibly predation by cats. The rufous owl and masked owl are natural predators.
Past clearing for agriculture, grazing, forestry and human settlement has reduced the total area of remaining mahogany glider habitat to around 110,000ha, less than 20 percent of the total area considered to be present at time of European settlement. The present population has been estimated to comprise about 1,500 individuals. Lack of suitable habitat in which young animals can disperse may be a constraint on further expansion of the population.
The mahogany glider, being highly mobile, requires more or less continuous vegetation cover to range freely. Infrastructure corridors such as major roads, railway lines and powerlines present barriers to movement along with clearing and settlement patterns in the landscape. A population viability analysis suggests that a minimum of 8,000ha of vegetation containing around 800 individuals is required for a localised population to remain viable. Presently, a number of large discrete patches of habitat survive.
Habitat fragmentation along the Bruce Highway that prevents mahogany glider dispersal. Photo: DERM
Decline in habitat quality has been occurring through a combination of al tered fire regimes (too much or too little), weed invasion and intensive grazing. Loss of habitat has been occurring in situations where sclerophyll forest is developing a rainforest understorey in the absence of fire. This trend is difficult to reverse using conventional management practices and has the potential to contribute to local extinction of mahogany gliders.
The recovery of the mahogany glider
The mahogany glider is a high profile species. Its conservation and recovery involves a broad range of people and works at all levels, from voluntary community actions to habitat protection provided by legislation and statutory mechanisms.
A recovery plan has been prepared for the mahogany glider under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. The recovery plan contains a comprehensive list of recommendations that guide investment in recovery actions for the species. Recent examples of recovery actions include an updated habitat map and erection of launching poles to enable mahogany gliders to cross the Bruce Highway at Easter Creek neat Ingham. Launching poles and a rope bridge fauna crossing have been installed at Corduroy Creek in a collaborative project involving state and local government, landholders, road builders, Traditional Owners and the Tully Branch of the Wildlife Protection Society of Queensland.
Around 45 percent of surviving mahogany glider habitat is contained within lands managed by the Department of Environment and Resource Management (DERM). Remnant vegetation that is mahogany glider habitat on other land tenures is protected from further loss through the Vegetation Management Act (1999) and through the Far North Queensland Regional Plan 2009-2031 that is a statutory plan under the Integrated Planning Act (1997).
The distribution of mahogany glider habitat. Image: DERM
The recently introduced Queensland Government Environmental Offsets Policy allows for any habitat loss associated with major projects to be offset through regrowth or tree planting. Offsets are potentially useful in expanding the size of remnant patches and for connecting remnants. The Far North Queensland Regional Plan 2009-2031 identifies “strategic rehabilitation areas”, critical landscape linkages that are presently cleared or heavily fragmented. The objective of identifying strategic rehabilitation areas is to guide where landholders and stakeholders can direct habitat restoration. Plantings in strategically important landscape linkages have already been undertaken using trees and shrubs grown through a nursery program at local primary schools.
Artificial den boxes have been installed at selected sites of fragmented habitat on freehold property and DERM estate within the Cardwell area with the support of landholders. These are known to be used by mahogany gliders when animals are dispersing. With barbed wire fences causing mahogany glider death and injuries landholders are being encouraged to replace the top strand of barbed wire with plain wire. An average of two injured mahogany gliders require rehabilitation and care each year.
Last updated: 03 September 2009