Petaurus gracilis (De Vis, 1883)

Russell A. Mittermeier & Don E. Wilson, 2015, Petauridae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 52-565 : 563-564

11.

Mahogany Glider

Petaurus gracilis

French: Possum a queue fine / German: Mahagoni-Gleithornchenbeutler / Spanish: Falangero planeador gracil

Other common names: Ebony Glider, Slendertailed Glider

Taxonomy. Belideus gracilis De Vis, 1883 ,

Cardwell region, Queensland, Australia.

Historically this species was considered to be a subspecies or synonym of P. nor folcensis. Following its rediscovery in 1989, after an absence of sightings since 1886, its taxonomy was reviewed, and it was recognized as a distinct species in 1993. Monotypic.

Distribution. Coastal region of NE Queensland from Hull River near Tully S

to Ollera Creek, ¢.40 km S of Ingham, NE Australia.

Descriptive notes. Head-body 22-27 cm, tail 30-39 cm; weight 337-500 g (males) and 310-454 ¢ (females). This glider is distinctive for its large size, long, relatively short-haired tail, and buff to mahogany-brown belly. It is easily distinguished from the smaller Squirrel Glider, which occurs nearby (but with no apparent range overlap), and from Sugar Glider (P. breviceps), which occurs within its distribution, by its much larger size and greater body weight.

Habitat. Found in open woodland composed of a diversity of myrtaceous and fabaceous trees, including Eucalyptus , Lophostemon , Melaleuca , Corymbia , Acacia , and Albizia . Trapping observations have revealed that its presence is correlated with that of Clarkson’s bloodwood ( Corymbia clarksoniana), poplar gum ( Eucalyptus platyphylla), and open habitat with a small middle-canopy and upper-canopy cover.

Food and Feeding. The diet consists primarily of nectar and pollen from trees such a Eucalyptus , Corymbia , and Melaleuca , and insects. Sap from Albizia procera, Acacia mangum, Acacia crassicarpa, and Acacia flavescens is also consumed, as are arils (seed-coverings) from the aforementioned acacias and from A. flavescens, and mistletoe fruit from Amyema and Dendrophthoe (both Loranthaceae ). This glider relies on the seasonal cycles of flowering and fruiting to provide different foods throughout year. One study revealed that pollen constituted at least 30% by volume of the contents in six of eight fecal and intestinal samples examined; the study revealed that Myrtaceae and Xanthorrhoea ( Xanthorrhoeaceae ) are the most frequently visited flowers, but significant occurrences of Banksia (Proteaceae) pollen suggest that it, too, may also be used.

Breeding. Has a distinct breeding season between April and September/October. Litter size ranges from one to two, with an average of 1-5 young. Uses tree hollows as dens for sleeping and rearing young. First breeding occurs at ¢.12-18 months and young are weaned after 4-5 months.

Activity patterns. Nocturnal. During the day this species dens in leaf-lined hollows of various tree species, including Eucalyptus platyphylla, E. tereticornis, Corymbia clarksoniana, C. intermedia, Melaleuca viridiflora, and M. dealbata; females have an average offive dens and males an average ofsix. Studies of Mahogany Gliders have revealed that the amount of time spent active each night throughout the year ranged from eight to 10-1 hours, and did not change significantly between the wet and dry seasons. During the night they normally have one continuous period of activity; they occasionally return to the dens during the night for an average of 85 minutes, mean entrance and exit times being 22:59 h and 00:25 h, respectively. Foraging (feeding and traveling) accounts for greatest amount of time, ranging from 40% of the time outside the den in January to 77% in September. Overall mean time spent in foraging was 61%, remainder of night being spent stationary (mean 24-3%), grooming (mean 11-:8%), in the den and then re-emerging (mean 2:5%), or vocalizing (mean 0-3%). Activity comprised mostly the behaviors associated with foraging, feeding (44:9%), climbing (13-2%), and gliding (3%). Throughout the night individuals traverse an average distance of 1506 m (range 590-3420 m), with no significant difference between males and females in either continuous or fragmented habitat. They do, however, travel longer distances during late dry season/wet season and shorter distances during early to middle dry season. Similarly, individuals travelled farther when there was a high availability of nectar and pollen than when there was less to feed upon.

Movements, Home range and Social organization. The average home range size within continuous habitat is ¢.20 ha, overlap between home ranges of den mates being typically 86%, compared with overlap of only 11% with non-paired individuals, suggesting that this species forms socially monogamous pairs. These gliders have an average density of 0-24 ind/ha in continuous habitat and 0-16 ind/ha in fragmented habitat. Within the home ranges each pair has 6-13 dens, all typically in live trees of the family Myrtaceae , of which Eucalyptus platyphylla, E. tereticornis, and Corymbia clarksoniana are the most often utilized. The height of the dens from the ground ranges from 6-6 m to 33-3 m. A majority of den entrances face either west or south; given that the poor weather comes from the east to north-east, a south-facing or west-facing entrance may reduce the risk of rain entering the den.

Status and Conservation. Classified as Endangered on The IUCN Red List. This species is considered at risk because more than 50% of its habitat has been cleared and there is high likelihood of further clearing. It has one of the smallest distributions of any mammal, occurring only in the narrow, highly fragmented band of vegetation in north-east Queensland from the Hull River south to Ollera Creek, an area with a total north-tosouth distance of only 122 km and a width ofjust 5-10 km. The surrounding areas are occupied by the Squirrel Glider, which is known to occur within 26 km to the south, west, and north-west; in extensive rainforest to the north, neither species appears to occur. Within Mahogany Glider’s naturally limited distribution only a small amount of habitatis protected within national parks. A population viability analysis has proposed that populations of 400-700 individuals (2000-3500 ha) showed a decreasing trend in population size over a 100year period, suggesting that they are likely eventually to become extinct. A population of 800 individuals (4000 ha) was thought necessary for the size to stabilize; as only ¢.50% of available habitat appears to be occupied, an area of up to 8000 ha may be required in order to maintain a population of 800 individuals. Habitat loss and degradation are probably the most serious threats to this species. Forests are being cleared for sugar cane, bananas, pineapples, improved pasture, pine trees, and aquaculture, dramatically reducing habitat quantity and quality. Altered fire regimes and intensive grazing threaten the structure and ecological integrity of remaining habitat fragments through rainforest expansion, sclerophyll thickening, and weed invasion. The widening of major roads can also cause major disruption of the species’ movements. Further, the gliding membranes of gliders can become entangled on barb-wire fences, resulting in fatalities. Conservation actions from the recovery plan for this species include: (1) the updating of habitat-mapping and identifying areas for protection, restoration, and management; (2) identifying, managing, and monitoring habitats threatened by encroaching rainforest; (3) developing strategies to conserve Mahogany Glider habitat on private lands; (4) implementing habitat-recovery burns at key sites and improving weed control; (5) reducing threats arising from transport and easement corridors; (6) promoting a “Mahogany Glider-friendly” fencing scheme; (7) determining the genetic structure of Mahogany Glider populations; and (8) increasing public awareness and involvement in the recovery of the species.

Bibliography. Asari et al. (2010), Burnett et al. (2008), Dettmann et al. (1995), Flannery (1994a), Jackson (1999, 2000b, 2000c, 2000d, 2000e, 2001, 2008, 2011), Jackson & Claridge (1999), Jackson & Johnson (2002), Jackson & Thorington (2012), Jackson et al. (2011), Van Dyck (1993).

Figures

Distribution. Coastal region of NE Queensland from Hull River near Tully S to Ollera Creek, ¢.40 km S of Ingham, NE Australia.