Pseudocheirus occidentalis, Thomas, 1888

Russell A. Mittermeier & Don E. Wilson, 2015, Pseudocheiridae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 498-530 : 527

13.

Western Ring-tailed Possum

Pseudocheirus occidentalis

French: Possum ngwayir / German: \Westlicher Ringelschwanzbeutler / Spanish: Falangero de cola anillada occidental

Other common names: Ngwayir, Western Ringtail, Western Ringtail Possum

Taxonomy. Pseudocheirus occidentalis Thomas, 1888 ,

“ King George's Sound , [ Perth ], Western A[ustralia].”

This species has historically been considered a subspecies of P. peregrinus . Monotypic.

Distribution. SW Western Australia, restricted to coast from S of Bunbury to Waychinicup National Park (near Albany) and in suitable habitat inland, most notably at Perup Nature Reserve and surrounding state forest near Manjimup; recently found near the Harvey River and Collie (NE Bunbury).

Descriptive notes. Head-body 30-40 cm, tail 30-41 cm; weight 0.7-1.3 kg. Fur of the Western Ring-tailed Possum is short and a deep chocolate-brown to gray above and creamy white below. Fur on tail is very short and ¢.50-65% of distal end is creamy white.

Habitat. Coastal regions associated with forests of myrtle species such as peppermint tree ( Agonis flexuosa) and tuart ( Eucalyptus gomphocephala); farther inland in jarrah (E. marginata), wandoo (E. wandoo), and marri ( Corymbia calophylla) forest. There appears to be some degree of habitat partitioning or competition where the Western Ring-tailed Possum occurs with the Common Brush-tailed Possum (7richosurus vulpecula), but extent and effect of competition is not clear. The Western Ring-tailed Possum has also been recorded in stands of peppermint trees near the Harvey River and in jarrah/marri forest near Collie (north-east of Bunbury); however,its long-term persistence in these areas is not confirmed. It was formerly known from Casuarina woodlands in the Wheatbelt near Pingelly (south-east of Perth).

Food and Feeding. Leaves of peppermint tree appear to constitute 90-95% of the diet of Western Ring-tailed Possums. Where there are no peppermint trees, their diet consists mostly of marri and jarrah leaves.

Breeding. In coastal populations, breeding of Western Ring-tailed Possums occurs throughout most of the year, with peaks in April-June and October-December. Observations in jarrah forest revealed breeding activity in March-April, with a minor second peak in September—October. Peak in breeding during autumn and early winter may be to ensure that later stages of lactation and weaning, which impose greatest nutritional demands on females, occur in spring and summer when new leaves are abundant. The second peak in breeding in spring and summer appears to correspondence with the bimodal seasonal pattern of plant productivity that displays a second flush of leaf growth in autumn. Western Ring-tailed Possums typically give birth to a single young each year, but they can produce up to three young after 2—4 weeks of gestation. Young Western Ring-tailed Possums remain in the pouch, which contains four teats, for c¢.100 days. They are weaned at 6-8 months and disperse at 8-12 months. Young females generally remain in home ranges of their mothers. Young males disperse from their mothers’ home ranges when they are about seven months old at a weight of 600-700 g. Sexual maturity appears to occur at one year of age, and longevity is 4-6 years.

Activity patterns. Western Ring-tailed Possums are nocturnal and mostly arboreal, but they will travel on the ground when foraging or traveling if the canopy is not continuous. They are known to nest on or near the ground. Western Ring-tailed Possums construct dreys (nests) in tree hollows in midto upper tree canopies and sometimes lower to the ground, often using leaves and branches of peppermint trees. They may also construct dreys in protected sites such as dense understory vegetation or under sedges and reeds. Each individual uses 2-7 nest sites. During the day, Western Ringtailed Possums may be found sheltering in a variety of unprotected sites, under logs, or in rabbit burrows.

Movements, Home range and Social organization. Home ranges of several individual Western Ring-tailed Possums were estimated to be smaller than 1-2-5 ha, and density estimates were 0-1-4-5 ind/ha. Home ranges of females overlap those of their daughters; male home ranges only overlap a little with other females or other males. Mortality can be high at particular times of the year. For example, mortality rate in jarrah forests can be 84% in April-September, which are cooler and wetter months of the year. A seasonal decline in condition of Western Ring-tailed Possums has also been observed in the hottest months of the year in January-March.

Status and Conservation. Classified as Vulnerable on The IUCN Red List. The Western Ring-tailed Possum had a much wider distribution in 1970s, when it was found throughout much of the Wheatbelt in south-western Western Australia, but it was not necessarily continuously distributed. Remaining coastal populations of the Western Ring-tailed Possum are threatened by a variety of factors, including habitat loss from tree clearing and fragmentation of habitat as a result of urban development. Habitat modification and timber harvesting threaten inland populations. Other threats include predation by introduced Red Foxes (Vulpes vulpes), and where this predator has been controlled, predation by feral cats and native carpet pythons ( Morelia spilota); climate change, which is predicted to result in further declines in rainfall; road traffic; loss of peppermint trees from insect attack, dieback caused by a water mold that causes root rot, and myrtle rust; and increasingly frequent and severe fires, which, in addition to killing individuals, reduce food availability and shelter sites and open forests to greater predation by cats and foxes. Translocation programs of Western Ring-tailed Possums have been developed in an attempt to mitigate effects of habitat loss, but success of translocated populations has not been demonstrated at any of the release sites, and the primary release site (Leschenault Peninsula Conservation Park) has suffered a population decline. Conservation measures proposed for the Western Ring-tailed Possum include: implementing a monitoring program at sites selected to represent the range of habitats used by the Western Ring-tailed Possum to assess population changes and responses to Red Fox control and impacts of other management practices; identifying sites of high conservation value to the Western Ring-tailed Possum; conserving them on public lands; minimizing impacts of land development; educating the public, especially people living with or near populations of the Western Ring-tailed Possum; developing and implementing a suitable fire management plan; controlling populations of Red Foxes and feral cats; and retaining and planting peppermint trees.

Bibliography. Finlayson, Diment et al. (2010), Jones, How & Kitchener (1994a, 1994b), Jones, Meathrel & Calver (2004), Morris, Burbidge & Friend (2008), de Tores (2008a), de Tores, Hayward & Rosier (2004), de Tores, Rosier et al. (2008), Wayne et al. (2005).

Figures

13. Western Ring-tailed Possum (Pseudocheirus occidentalis), 14. Eastern Ring-tailed Possum (Pseudocheirus peregrinus), 15. Rock Ring-tailed Possum (Petropseudes dahl), 16. D’Albertis’s Ring-tailed Possum (Pseudochirops albertisii), 17. Green Ring-tailed Possum (Pseudochirops archeri), 18. Plush-coated Ring-tailed Possum (Pseudochirops corinnae), 19. Reclusive Ring-tailed Possum (Pseudochirops coronatus), 20. Coppery Ring-tailed Possum (Pseudochirops cupreus)

Distribution. SW Western Australia, restricted to coast from S of Bunbury to Waychinicup National Park (near Albany) and in suitable habitat inland, most notably at Perup Nature Reserve and surrounding state forest near Manjimup; recently found near the Harvey River and Collie (NE Bunbury).