The yellow-bellied glider, also known as the fluffy glider in Far North Queensland, is a member of the Petauridae family. It is the largest of the four Petaurus gliders that occur in Australia.
The yellow-bellied glider lives in family groups and is the most vocal of all gliders. It is an extremely accomplished glider and can readily be found at trees which it taps for sap.
Two genetically distinct populations are recognised in Queensland:
- the subspecies Petaurus australis reginae as far north as Mackay
- an isolated population in Far North Queensland referred to as Petaurus australis (Wet Tropics, or northern subspecies).
Yellow-bellied gliders are greyish brown in body colour with a distinct black stripe down their back from the forehead to tail.
The gliding membrane has a black margin and there is a black stripe down the outer side of the limbs to the paws. Belly colour is lighter and can vary from creamy white, the predominant colour in the most northerly population in Queensland, to yellowish-orange, particularly in older animals in more southerly populations. Hence its common name. Ears are black and naked.
- Head-body length, males 26-30 averaging 28 cm, females 24-31 averaging 27 cm
- Tail length, males 39-46 averaging 27 cm, females 38-47 averaging 43 cm
- Weight, males 470-725 averaging 595 grams, females 435-660 averaging 520 grams
- Animals in the northern Wet Tropics population are smaller than their southern cousins, on average males are 100 grams lighter and females 50 grams.
The gliding membrane (patagium) stretches from the fifth finger of the hand to the ankle, giving it a relatively large patagium to body ratio. It has a gliding trajectory of about 30 degrees to the horizontal and shows considerable manoeuvrability as it is capable of making 180 degree turns in mid-air.
Glides over 100 m are known, 90 to 100 metres are not exceptional and 40 to 60-metre swoops are common. Gliding enables the glider to cover great distances rapidly. In one four hour period a glider travelled two kilometres and they regularly move up to 500 m from their den tree to feed.
Most readily found by watching trees at night with fresh feeding incisions, often triangular or v-shaped, oozing sap on the trunks of trees or by listening for their loud calls that can be heard from up to 500 metres away.
Ecology and behaviour
- In south-eastern Queensland, the glider’s habitat is dry sclerophyll open forest containing smooth-barked eucalypts that shred their bark in strips, has a moderate rainfall (650-1200 mm). In the south-east, the glider shows a clear preference for forest types dominated by gum-barked and winter flowering eucalypt species, which provide continuous exudate and invertebrate foraging opportunities. The glider tends to avoid wet sclerophyll forests and rainforest.
- The Wet Tropics population is confined to a narrow band, 300 km long but no more than 5 km wide and usually less than 1 km wide with numerous gaps, of tall to very tall eucalypt open forest containing rose gum (Eucalyptus grandis) and red stringybark (Eucalyptus resinifera) above 600 m in altitude.
Births occur throughout the year in Queensland, with a peak in winter months. Females give birth to a single young annually with only one know record of twins. Young remain in the pouch for up to 100 days, are then transferred to a den where they remain for about 50 days before beginning independent foraging. Individuals commence breeding when between 18 months and two years old.
The yellow-bellied glider is an insect, pollen and exudate feeder. They derive their protein from insects and pollen, and energy from nectar, honeydew, manna and tree sap.
- A favourite hunting place for insects, particularly large crickets, is under the shredding bark of gum trees.
- Pollen is mainly obtained from eucalypts, turpentine and banksia trees and the contents of the hard-shelled pollen grains digested.
- Honeydew is secreted from sap-sucking bugs and is licked from branches by the gliders.
- They also forage on the leaves of eucalypts for manna and lerps.
- They obtain clear sweet tasting sap of eucalypts by making V-shaped incisions with their lower incisors into the trunk bark of a number of different species.
- Sap is a resource available year-round, whereas nectar and insects are seasonal and at times scarce. Trees tapped for sap are several.
- In south-eastern Queensland 12 species of eucalypt are known, eight gums, three stringybarks and one bloodwood plus one acacia for its gum. Up to three species at any one locality may be tapped for sap, but usually, only one is used.
- The red stringybark Eucalyptus resinifera is the only tree known to be tapped for its sap by the Wet Tropics population over its whole range.
Family Groups and Home Range
The yellow-bellied glider lives in family groups with up to six individuals in a group. The group typically consists of an adult male and female with a number of subadult offspring. The adult male and female may maintain a consistent monogamous pair over a number of years and the probability of the male fathering the young in his groups has been shown genetically to be 80 per cent in a South Australian population. Nevertheless, group composition can vary considerably to include multiple male, multiple female and even single-sex adult groups.
Group home ranges overlap little and intruders are attacked, sometimes resulting in severe injuries, even death. Group home ranges can vary in area from 25 to 120 hectares, with estimated densities of gliders from 0.05 to 1.6 per hectare. Home range and density will depend largely on the resources available to the gliders.
The gliders use their wide range of calls to communicate amongst themselves and as territorial calls to repel intruders. Their calls include loud shrieks, moans, whirring moans, gurgling, purring, chirruping, panting and clicking. They also have a number of scent glands, on the forehead (males only), sternum and cloacally which they use to rub on each other and on branches.
The glider occurs down the east coast of mainland Australia from the Mount Windsor Tableland, west of Mossman in Far North Queensland, to the Victorian South Australian border. In south-east Queensland, the glider is widely dispersed, but with a highly localised distribution, with possible disjunct populations in the Mackay and Carnarvon areas.
The most northerly population in Queensland occurs along the western edge of the Wet Tropics bioregion and is isolated by a gap of about 400 kilometres from the next population to the south on the Clarke Ranges inland from Mackay. The Wet Tropics population is divided into three distinct subpopulations.
- Habitat loss and fragmentation due to timber-harvesting, agriculture and dwellings are the main threats to this species. Due to past forest management, there is a current dearth of available live hollow-bearing trees within yellow-bellied glider habitats of south-east Queensland. Remaining dead trees are therefore an important resource, but these are at risk of collapse due to regular prescribed burning regimes and windthrow.
- In Queensland broad-scale land clearing has been stopped due to vegetation management legislation. However, degradation to existing habitat (e.g., through fire, timber removal) within the habitat of isolated populations, but also between non-isolated populations, is a huge threat to the species (essentially inducing a fragmentation effect) throughout its range, due to its wide-ranging and extensive habitat requirements.
- Rainforest encroachment of glider habitat in North Queensland is estimated to have ‘captured’ 70 per cent of tall open forest dominated by rose gum and 50 per cent dominated by mixed species of eucalypts over a period of 50 years. Gliders may continue to use rainforest containing emergent eucalypts, but eventually, the rainforest will totally replace the glider’s habitat.
- Barbed wire fences are a localised threat.
- Introduced predators, cat and fox, are a threat of unknown magnitude.
- The disjunct nature of the glider populations makes them susceptible to local extinctions mainly as a result of habitat degradation and climate change.
- Wet Tropics population – Vulnerable (Nature Conservation Act 1992)
- SE Queensland populations – Least Concern (Nature Conservation Act 1992)
- Wet Tropics population – Vulnerable (Environment Protection and Biodiversity Conservation Act 1999)
- IUCN: Least Concern (2008 Red List)
- Habitat management is of prime importance. In Far North Queensland proactive management of habitat through planned fire strategies is paramount. Fire is required to prevent rainforest capture of the glider’s habitat, but without overly causing the loss of large rose gum den trees. In southern Queensland, where much of the glider’s habitat is in spotted gum forest types which have high commercial timber values, management needs to mitigate the effects of logging which reduces the average size of trees with a resulting decrease in nectar and insect food resources for the glider.
- Where possible, populations that have become disjunct through habitat clearing need to be reconnected by the planting of tree corridors.
- Limit the danger and fragmentation of habitat caused by the use of barbed wire fences and wide linear clearings for roads, power lines and fire breaks.
- Use of nest boxes as a management tool for re-establishing populations of hole-denning of other glider species in areas where holes are scarce either because of their reduction through past management practices, or in newly planted habitat. While other species of Petaurus gliders are known to use nest boxes, the effectiveness of nest boxes for yellow-bellied gliders is yet to be established.
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