Biodiversity

Species Profile and Threats Database


For information to assist proponents in referral, environmental assessments and compliance issues, refer to the Policy Statements and Guidelines (where available), the Conservation Advice (where available) or the Listing Advice (where available).
 
In addition, proponents and land managers should refer to the Recovery Plan (where available) or the Conservation Advice (where available) for recovery, mitigation and conservation information.

EPBC Act Listing Status Listed as Vulnerable
Listing and Conservation Advices Commonwealth Conservation Advice for Pseudocheirus occidentalis (Western Ringtail Possum) (Threatened Species Scientific Committee (TSSC), 2013fu) [Conservation Advice].
 
Recovery Plan Decision Recovery Plan required, included on the Commenced List (1/11/2009).
 
Adopted/Made Recovery Plans
Other EPBC Act Plans Threat Abatement Plan for Predation by the European Red Fox (Department of the Environment, Water, Heritage and the Arts (DEWHA), 2008zzq) [Threat Abatement Plan].
 
Policy Statements and Guidelines Survey guidelines for Australia's threatened mammals. EPBC Act survey guidelines 6.5 (Department of Sustainability, Environment, Water, Population and Communities (DSEWPaC), 2011j) [Admin Guideline].
 
EPBC Act Policy Statement 3.10: Significant impact guidelines for the vulnerable western ringtail possum (Pseudocheirus occidentalis) in the southern Swan Coastal Plain, Western Australia (Department of the Environment, Water, Heritage and the Arts (DEWHA), 2009) [Admin Guideline].
 
Background Paper to the EPBC Act Policy Statement 3.10: Significant impact guidelines for the vulnerable western ringtail possum (Pseudocheirus occidentalis) in the southern Swan Coastal Plain, WA (Department of the Environment, Water, Heritage and the Arts (DEWHA), 2009ae) [Admin Guideline].
 
Information Sheets Western ringtail possum, Pseudocheirus occidentalis Threatened Species Day Fact Sheet (Department of the Environment and Water Resources (DEWR), 2007bc) [Information Sheet].
 
EPBC Act Policy Statement 3.10 - Figure 1 (Department of the Environment, Water, Heritage and the Arts (DEWHA), 2008adc) [Information Sheet].
 
Federal Register of
    Legislative Instruments
Declaration under s178, s181, and s183 of the Environment Protection and Biodiversity Conservation Act 1999 - List of threatened species, List of threatened ecological communities and List of threatening processes (Commonwealth of Australia, 2000) [Legislative Instrument].
 
State Government
    Documents and Websites
WA:Ringtail Possum (Pseudocheirus occidentalis) Recovery Plan (Department of Parks and Wildlife (DPaW), 2014a) [State Recovery Plan].
WA:Fauna Species Profiles - Western Ringtail Possum Pseudocheirus occidentalis (Thomas, 1888) (Western Australia Department of Environment and Conservation (WA DEC), 2010n) [Information Sheet].
State Listing Status
WA: Listed as Vulnerable (Wildlife Conservation Act 1950 (Western Australia): September 2013 list)
Non-statutory Listing Status
IUCN: Listed as Vulnerable (Global Status: IUCN Red List of Threatened Species: 2013.1 list)
Scientific name Pseudocheirus occidentalis [25911]
Family Petauridae:Diprotodonta:Mammalia:Chordata:Animalia
Species author  
Infraspecies author  
Reference  
Distribution map Species Distribution Map

This is an indicative distribution map of the present distribution of the species based on best available knowledge. See map caveat for more information.

Illustrations Google Images
http://www.margaret-river-online.com.au/mammals/ringtail.htm ;
http://raq1.swisp.net.au/users/ringtail/

Pseudocheirus occidentalis has occasionally been placed in synonymy to the Common Ringtail Possum (Pseudocheirus peregrinus) (e.g. Ride 1970), which occurs in eastern Australia. However, its distinctiveness is widely accepted, despite no published analyses of comparative morphology or molecular profiles (Woinarski et al. 2014). Unpublished morphological and karyotype evidence (McKay 1984; Murray et al. 1980) supports its specific status, but there is contradictory evidence from electrophoretic studies and albumin immunology (Baverstock et al. 1990).

The Western Ringtail Possum is a medium sized nocturnal marsupial, up to 1.3 kg in weight and approximately 40 cm in body length. Its fur is dark brown above with cream to grey fur underneath. Its ears are shorter and rounder in comparison with the larger Common Brushtail Possum (Trichosurus vulpecular). This species strong prehensile tail grows to 41 cm long and ends in a white tip (Van Dyck & Strahan 2008).

Current distribution

The Western Ringtail Possum has a patchy distribution in predominantly two areas: near Bunbury to Leeuwin-Naturalisete National Park (with a small translocated subpopulation near Dawesville); and near Albany (Jones pers. comm. cited in Woinarski et al. 2014). Woinarski and colleagues (2014) postulate that these two areas contain the only two subpopulations of the species. Much of the habitat remnants in this area occur on private land (Woinarski et al. 2014). There are records of the species in urban and peri-urban areas (Albany, Augusta, Busselton) (Jones et al. 1994b), especially in areas where mature stands of the Peppermint Tree (Agonis flexuosa) occurs (Harewood 2008 cited in Shedley & Williams 2014).

The largest inland subpopulation, in the Upper Warren region, had declined since 1998 (Shedley & Williams 2014) to near extirpation by the late 2000s, with a 95% decline in sightings from spotlight surveys (Wayne et al. 2012 cited in Woinarski et al. 2014). There are a few post-2000 inland records of the species between Yornup in the north to Northcliffe in the south, Carey forest block in the west and Lake Muir in the east (Jones pers. comm. cited in Woinarski et al. 2014).

The southern Swan Coastal Plain (Bunbury to Dunsborough) is of particular importance for the Western Ringtail Possum as it: supports the largest and most dense subpopulation; provides the greatest potential for recruits to adjoining areas; supports dense and productive Peppermint Tree stands; and provides habitat where the Brushtail Possum (Trichosurus vulpecula) does not co-occur (DEWHA 2009; Shedley & Williams 2014). The subpopulation in this area are frequently associated with urban or semi-urban areas, but this may reflect greater survey effort in these parts (Shedley & Williams 2014).

Using post-1995, records the extent of occurrence of the Western Ringtail Possum is estimated to be 7155 km² and its area of occupancy is estimated to be 3700 km² (DEC 2007). More recently, Woinarski and colleagues (2014) provide an extent of occurence of 40 400 km² (with a decreasing trend) and an area of occupancy of <500 km² (with a declining trend).

On the recommendation of the interim recovery plan (Burbidge & de Torres 1997), subpopulations have been translocated to: Leschenault Peninsula Conservation Park; Yalgorup National Park (White Hill and Preston Beach); Crampton Nature Reserve; Lane Poole Reserve and Keats Forest Block (south-east of Dwellingup); Karakamia Sanctuary, Chidlow; and Locke Nature Reserve (as a pilot study) (DEC 2007). Only the releases to Yalgorup NP (some animals establishing at nearby Dawesville) and Karakamia Sanctuary (<50 mature individuals persisting) have been successful (Woinarski et al. 2014). Failure of reintroductions have been blamed on European Red Fox (Vulpes vulpes) and feral Cat (Felis catus) predation and poor-quality food resources (Woinarski et al. 2014).

Historic distribution

Historically, the Western Ringtail Possum occurred throughout much of south-west Western Australia (Maxwell et al. 1996). Early records indicate that species occurred from north of Perth to around Cranbrook and the Pallinup River in the south-east (Burbidge & de Tores 1997). Sub-fossils of the species have been found south-east of Geraldton and on the southern edge of the Nullarbor Plain (see Woinarski et al. 2014).

By 1980, the Western Ringtail Possum had been lost from 80% of its original range (Jones 2014 cited in Woinarski et al. 2014). At this time, it persisted in the coastal strip between Bunbury and Albany (extending inland in riparian habitat between the Collie and Blackwood Rivers), and in the Upper Warren region (Perup Nature Reserve, Greater Kingston National Park and adjacent state forest) (Burbidge & de Tores 1997; Wayne et al. 2006). This species was lost from all drainage systems between the Avon and Harvey river systems during the 20th century (Jones 2000). In inland areas, it was regularly recorded in Tutanning Nature Reserve near Pingelly in the 1970s (de Tores et al. 2005a cited in Shedley & Williams 2014) but is now mostly extinct from the majority of the northern and inland areas of its range (Shedley & Williams 2014). Wayne and colleagues (2006) indicate that high value habitat for the species has been selectively cleared for agriculture, owing to the area's fertile and productive nature. The species feeds and moves in the canopy, limiting their ability to disperse and recolonise habitat in fragmented landscapes (DEC 2007).

In 2012, there was no regular monitoring across the species range, but there has been limited opportunistic monitoring (Woinarski et al. 2014). A field survey of 61 sites during 1990–1992 located Western Ringtail Possums at 20 localities, scattered over a large area of south-west Western Australia from Collie River to Two Peoples Bay. Of these locations, 15 are in conservation areas and one is an urban location in Busselton. Other subpopulations associated with urban environments exist in East Augusta and Albany (Jones et al. 1994a). Earlier collecting localities are listed in Kitchener and Vicker (1981). During this 1990–1992 survey, total population numbers were not estimated. However, in localities where densities were calculated, or population size could be counted, estimates of local population size ranged from seven to 104 individuals. As these numbers are generally very low, and given the high level of predation by the European Red Fox (Jones et al. 1994b), such subpopulation cannot be considered secure.

Woinarski and colleagues (2014) suggest that the Western Ringtail Possum has an abundance of <8000 with a declining trend. A total population size of 2000-5000 has been estimated in the Bunbury to Dunsborough area (Shedley & Williams 2014). There has been an estimated decline in abundance of >80% in the 2000s (Woinarski et al. 2014). Declines have been observed in the Busselton, Albany, Upper Warren and Ludlow National Park areas (Woinarski et al. 2014).

Subpopulation density of the species vary, but most remnants contain few animals (Woinarski et al. 2014). Variation in density is due to variations in vegetation structure and composition, proximity to creeklines or wetlands, is likely to be associated with social groupings and is likely to vary within vegetation blocks (Shedley & Williams 2014). Some remnants have very high densities, with >10 individuals per hectare oberverd in a number of post-2007 surveys in the Busselton area (Shedley & Williams 2014). One study observed 39 per hectare over a four year period (equating to nine mature Peppermint Trees per possum), but 33% of trees were removed with a resulting 38% reduction in the number of mature possums present (Jones pers. comm. cited in Shedley & Williams 2014).

Wayne and colleagues (2006) found that the abundance of Western Ringtail Possums, on public land, was highest in Perup Nature Reserve. They state that most of the state forests in which Western Ringtail Possums survive have been incorporated into the reserve system (national parks, nature reserves and 'Fauna Habitat Zones'). In general, the nature reserves and national parks where this species has been found are managed for the conservation of flora and fauna, but not specifically for the management of the Western Ringtail Possum (DEC 2007). Forty hectares of Peppermint Tree forest is protected at Locke Estate (Jones et al. 1994).

Habitat parameters affecting the distribution of the Western Ringtail Possum are well known (e.g. DEWHA 2009; Jones & Hilcox 1995). The subpopulation on the Swan Coastal Plain are associated with stands of myrtaceous trees (usually Peppermint Tree (Agonis flexuosa)) growing near swamps, water courses or floodplains, and at topographic low points which provide cooler, often more fertile, conditions (Jones 2001 cited in DPaW 2014; de Tores et al. 2004). In an assessment of habitat suitability for the species on the southern Swan Coastal Plain, Shedley and Williams (2014) found that the main variables that are likely to define suitable habitat to be:

  • presence and dominance of myrtaceous foliage, in particular that of Peppermint Tree
  • foliage that is higher in nitrogen and moisture, and lower in certain phenolic compounds
  • presence of dense shade and drinking water to reduce the impacts of heat stress
  • presence of suitable tree hollows and other day time rest sites
  • dense vegetation structure that provides protection from introduced and native predators
  • areas with lower predation pressures or are baited to achieve this
  • high connectivity of tree canopies and habitat patches to allow safe movement of individuals
  • areas without high intensity fires, that have significant direct and indirect impacts on survival of individuals.

The subpopulation in the southern forests, near Manjimup occur mainly in Jarrah (Eucalyptus marginata) or Marri (Corymbia calophylla) dominated forests extending to Wandoo (Eucalyptus wandoo) forests to the north-east of Manjimup (DPaW 2014a). They also occur in Karri (Eucalyptus diversicolor) forest from Northcliffe to west of Manjimup (DEC 2012c cited in DPaW 2014a). In the Jarrah/Marri forests around Manjimup the highest relative abundance occurs in areas with limited anthropogenic disturbance (unlogged or lightly logged, and a low intensity and low frequency fire history), that are intensively fox-baited and have low indices of fragmentation (Wayne et al. 2005a, 2006).

On the South Coast, near Albany the Western Ringtail Possum is found in coastal heath, Jarrah/Marri woodland and forest, Peppermint Tree woodland, myrtaceous heaths and shrublands, Bullich (Eucalyptus megacarpa) dominated riparian zones and Karri forest (DPaW 2014a). In the vegetation associations mapped in the Albany urban area by Sandiford and Barrett (2010 cited in DPaW 2014a), most records were from coastal limestone heath vegetation unit 5b. Little is known of the relative abundance of the Western Ringtail Possum within and between vegetation types, including the vegetation types where they have been recorded in the broader Denmark to Mt Manypeaks area.

The Western Ringtail Possum is also found within plantations of Pine (Pinus spp.) and Blue Gum (Eucalyptus globulus) typically within remnant vegetation associated with drainage lines and watercourses through plantations. Dreys (constructed nests) have been constructed within these species (Williams pers. obs. cited in DPaW 2014a). Dreys and animals have also been sighted in exotic tree plantations, particularly along edges next to native forest, around Manjimup (Wayne pers. comm. 2013 cited in DPaW 2014a). It is suspected that these plantations may provide shelter but depending on the species, are unlikely to be a food source (Williams pers. comm. 2013 cited in DPaW 2014a).

At Locke Nature Reserve, temporal patterns of grazing and fire may have affected the growth and form of Peppermint Trees and understorey components. In particular, increased browse quality in ten-year-old regrowth may have encouraged a female-biased sex ratio and rapid expansion of the local population (Jones et al. 2004, 2007 both cited in Shedley & Williams 2014).

High Western Ringtail Possum population densities have been recorded in urban settings, particularly where mature peppermint trees have been retained which have large, dense and overlapping canopies (Harewood 2008). This habitat type appears to provide a variety of browse items, artificial watering which buffers vegetation against the impacts of a drying climate, alternative habitat connections (fences, powerlines) and alternative shelter/roosts in buildings. It is possible that the Western Ringtail Possum has benefited from this development and adapted to the urban setting (Shedley & Williams 2014).

The Western Ringtail Possum has a low breeding capacity, a relatively short lifespan and a high susceptibility to predation (DEC 2007). Individuals are naive, displaying minimal predator avoidance, and has a minimal immune response to infection (de Tores et al. 2008).

The generation length of the Western Ringtail Possum is two to three years (DEC 2007) and the oldest observed individual in Jarrah forest is four years (Wayne et al. 2005c). In Jarrah forest, seasonal declines in condition commence during the hottest months of the year (January–March), but mortality (84% of deaths) occurs primarily between April and September (Wayne et al. 2005c).

Reproduction

Females breed once a year, giving birth to one to three pouch young (normally one) (Jones 2000). In the southern Jarrah forest, most of the breeding activity of the Western Ringtail Possum occurs in March-April with a minor second peak in September-October (Wayne et al. 2005c). In coastal subpopulations, breeding occurs throughout most of the year (with peaks in April-June and October-December) (Jones et al. 1994b).

As breeding predominantly occurs in autumn, the later stages of lactation and weaning, which requires the highest nutritional demands, occur in spring and summer when new shoots are abundant (Jones et al. 1994a; Wayne et al. 2005c). South-west Western Australia observes a bi-modal seasonal pattern of plant productivity that can present a second growth leaf growth flush in autumn. This coincides with the weaning of offspring from the second breeding peak (Wayne et al. 2005c).

After two to four weeks of gestation, pouch young remain in the pouch for three to four months (Jones et al. 1994a). The young are weaned at six to eight months and disperse at 8-12 months (How 1978 cited in Wayne et al. 2005c). Breeding commences at 12 months of age (Ellis & Jones 1992; Wayne et al. 2005c). 

Wayne and colleagues (2005c) speculate that female sex ratio bias indicates an expanding population size in high quality habitat and that male bias may indicate marginal or declining resource conditions (Jones 2004 and Jones et al. 2004 cited in Wayne et al. 2005c).

The diet of the Western Ringtail Possum consists almost entirely of myrtaceous leaves (Smith 1983 cited in Jones & Hillcox 1995), the major component (79-100%) of which is foliage from the Peppermint Tree. Where Peppermint Tree is absent, the diet consists mostly of Marri and Jarrah leaves (Jones et al. 1994b), and also occurred in Wandoo and Sheoak sites in the wheatbelt. Although arboreal, the species is known to descend to the ground when foraging (de Tores & Rosier 1997).

In the Bunbury to Dunsborough region, has been observed feeding on new shoots, flowers, leaves and/or fruiting bodies from a range of flora including Western Australian Christmas Tree (Nuytsia floribunda), Golden-wreath Wattle (Acacia saligna), Native Wistaria (Hardenbergia comptoniana), Western Sheoak (Allocasuarina fraseriana), Tuart, Flooded Gum (Eucalyptus rudis), Melaleuca viminea, M. cuticularis, M. rhaphiophylla, Kunzea glabrescens and Western Woody Pear (Xylomelum occidentale) (Harewood pers. comm., Webb et al. unpub. data, Clarke 2011 all cited in Shedley & Williams 2014). At other sites, it has been observed feeding on Karri (E. diversicolor), Bullich (E. megacarpa), Yarri (E. patens) and Pine (Pinus radiata) (Gilfillan 2008, Harewood pers. comm. both cited in Shedley & Williams 2014). In the Bunbury to Dunsborough region, highest relative abundance of Western Ringtail Possum in wetlands without Peppermint Tree was confined to areas where browsing was confined to Melaleuca viminea, M. cuticularis and M. rhaphiophylla (Molloy unpub. data cited in Shedley & Williams 2014) and outside of this region, Kunzea glabrescens is the main food source (Shedley & Williams 2014).

Like most possums, the Western Ringtail Possum is active at night and tends to shelter during the day. Shelter sites vary from rests sites with no apparant protection, dreys (constructed nests), or sites that offer natural protection (tree hollows (particularly in large eucalypts), dense understorey, forest debris, under logs, hollow logs, under sedges and reeds, grass trees canopies or down rabbit burrows) (de Tores & Rosier 1997; Wayne 2005). Jones and colleagues (1994b) found that dreys were only common in near-coastal Peppermint Tree forest and tree hollows as rest sites were more common in inland areas. Although arboreal, the species is known to descend to the ground for foraging or when the overstorey is discontinuous (de Tores & Rosier 1997).

The home range of the Western Ringtail Possum is usually less than 5 ha (Jones 2000). As a result of nutrient limitations, larger home ranges are observed in the Jarrah forest subpopulation compared to near the coastal subpopulation around Busselton (Wayne et al. 2005c). In one study, home ranges of radio-collared individuals varied from 0.07 to 1.0 ha for females and roughly double that for males. Female home ranges overlap mainly in mother-daughter pairs and male home ranges have only a little overlap with either females or other males. Dispersal is most likely limited, with most animals remaining close to their natal range (Jones et al. 1994b). Western Ringtail Possums may use as many as six shelter/refuge trees in their home range (Ninox Wildlife Consulting 1999b).

The Western Ringtail Possum can be distinguished from the Common Brushtail Possum (Trichosurus vulpecula) by its smaller rounded ears and thin prehensile tail, which is as long as its body (Van Dyck & Strahan 2008).

In Jarrah forest, Wayne and colleagues (2005a) found repeated spotlighting provides similar or better detection rates than extensive trapping and requires substantially less effort. Spotlighting, however, requires repitition and careful analysis to be useful (de Tores et al. 2004; Wayne et al. 2005b). Spotlighting results may be affected by skill differences between observers, seasonal/weather conditions and survey speed (when surveys are conducted in vehicles) (de Tores & Rosier 1997; Wayne et al. 2005b). Detection may be inversely related to the amount of rain recorded on the day of the survey (Wayne et al. 2005b). At low population density, the species may remain undetected from spotlighting and faecal pellet surveys (de Tores & Rosier 1997).

Scat scoring, which has been correlated to spotlighting counts, is a significantly better and more cost-effective monitoring method (Wayne et al. 2005a; Jones pers. comm. cited in Woinarski et al. 2014). However, in areas of dense understorey or heavy litter the method is not effective, and such methods may only be useful in open bushland with consistent site conditions (de Tores & Elscot 2010). In larger habitat patches, the most reliable estimate of abundance and density is determined using line-transect distance sampling (de Tores & Elscot 2010).

Dreys (constructed nests) are made from fine to medium-sized material collected from overstorey and understorey vegetation. Dreys vary from flimsy or platform-like constructions providing minimal shelter, to elaborate constructions providing substantial protection (de Tores & Rosier 1997). It is not always possible to identify whether Western Ringtail Possums or other animals are using the dreys (Ninox Wildlife Consulting 1999a). The absence of dreys does not mean that the species is absent and in the lower Collie River valley dreys are rare and at Perup possums were only recorded in tree hollows (Jones et al. 1994a).

Western Ringtail Possums are rarely caught in traps and conventional trapping techniques are inappropriate for detecting their presence (de Tores & Rosier 1997). Nevertheless, arboreal traps are superior to ground traps. A study using arboreal cage traps caught 9.3 times as many Western Ringtail Possums as ground traps. An advantage of arboreal traps is that non-target terrestrial species are not caught unnecessarily and more traps are left available to catch possums (Wayne et al. 2005a). Bait type did not significantly affect capture rates of Western Ringtail Possums in a study that compared the use of universal bait over Eucalyptus oil baits (Wayne et al. 2005a). Baiting success may vary as a result of seasonal differences in nutritional demands and dietary differences in food types, quality and quantity.

To maintain population size a female Western Ringtail Possum needs a minimum of two successful reproductive seasons and 100% offspring survival to maturity, anything that negates this may threaten the viability of the species (Wayne et al. 2005c). Woinarski and colleagues (2014) provide the following threat assessment:

Threat Consequence rating Extent  
Climate change and extreme weather events Currently severe-catastrophic, potentially catastrophic Entire The Western Ringtail Possum is sensitive to heat and drought-induced stress (Jones et al. 1994b). Acute population size declines have been observed associated with the drying climate of south-west Australia, which is increasing the prevalence of heat waves and drought (Woinarski et al. 2014). Winter rainfall in the area has declined by about 20% since the 1980s and this trend is likely to continue (McFarlane 2005; Cleugh et al. 2011, Indian Ocean Climate Initiative 2012 both cited in Woinarski et al. 2014).

Predation, declines in extent of local and regional habitat and declines in quality of habitat increase the impact of dry conditions on the Western Ringtail Possum. Drought affects food quality (Jones pers. comm. cited in Woinarski et al. 2014) and drought decreases the condition of the subpopulation in Jarrah forest (Wayne et al. 2005c). The distance of local populations to water sources and whether water sources are perennial may indicate a local populations' risk to threats associated with dry conditions (de Tores et al. 2004).
Predation by the European Red Fox (Vulpes vulpes) and the Cat (Felis catus) Severe-catastrophic Entire The Western Ringtail Possum is predator naive and highly susceptible to infection (which could result from interaction with predators) (de Tores et al. 2008). Change in forest structure through logging or clearing have resulted in the Western Ringtail Possum travelling and resting more frequently on the ground (Wayne et al. 2006), which makes them more susceptible to predation (Burbidge & de Tores 1997; Jones et al. 1994b). Subsequently, the species is now largely restricted to areas with dense canopy where they do not need to come to the ground and where they can survive in the absence of European Red Fox or Cat control (Woinarski et al. 2014).

Successful European Red Fox baiting programs may switch other predators (Cat, pythons (Morelia spp.) and Chuditch (Dasyurus geoffroii)) from preying on rabbits to preying on the Western Ringtail Possum (also known as mesopredator release) (de Tores et al. 2008). Mesopredator release has been quantified at Leschenault National Park where Cat and python numbers have heightened following European Red Fox control (de Tores et al. 2008).
Inappropriate fire regimes Severe Entire Western Ringtail Possum abundance is negatively associated with greater fire intensity (Wayne et al. 2006). Fire in fragmented coastal Peppermint Tree forest can eliminate subpopulations (Woinarski et al. 2014). Fire can remove dense canopy making the species more likely to be predated and limiting food availability (Wayne et al. 2006; Woinarski et al. 2014). Individuals may starve during the three to four months that it takes for sufficient new growth to provide a replacement food source after large-scale, intense fire. Low intensity patch burning practiced by Nuyngar peoples in Jarrah forest would favour heterogeneity in vegetation structure and fuel age, thus providing habitat refuge, as well as limiting the opportunity for large scale fire events (Wardell-Johnson et al 2004).
Habitat loss and fragmentation Severe Large Clearing and fragmentation of inland and coastal habitat has significantly impacted the Western Ringtail Possum throughout its range. In the south-west, clearing for agriculture has been concentrated on land adjacent to waterways. These are areas that typically support the highest density populations (e.g. areas with the Peppermint Tree and/or a cooler microclimate) and clearing of these areas has the greatest impact on the species (Jones et al. 1994a; de Tores et al. 2008; Wayne et al. 2006).

Fragmentation of coastal Peppermint Tree forest associated with urban, semi-urban, tourist and sand mining development is an ongoing threat, particularly in the Bunbury, Busselton and Albany areas. The ongoing requirement for housing and for industry in the greater Busselton area will continue to result in habitat loss and population displacement (Burbidge & de Tores 1997; de Tores et al. 2004; DEC 2007; Jones et al. 1994; Jones & Hillcox 1995). Most coastal Peppermint Tree forest occurs outside of managed reserves.
Tree decline and insect outbreaks Moderate-severe Minor-moderate Coastal Peppermint Tree decline, gum leaf skeletoniser and Phytophthora dieback in Jarrah, Tuart decline and other tree declines have resulted in extensive but localised reductions in food and habitat quality (Jones pers. comm. cited in Woinarski et al 2014). If Myrtle Rust (Puccinia psidii s.l.) is introduced, it will significantly impact Western Ringtail Possum subpopulations as the Peppermint Tree is highly susceptible to the pathogen (Woinarski et al 2014).
Logging Moderate Minor Timber harvesting and burning operations can result in habitat loss, habitat fragmentation, loss of nest trees and refuges, loss of canopy and population displacement. Western Ringtail Possums are more abundant in unlogged forest or where logging has been least intense (Wayne et al. 2006). Many of the known populations are outside areas available for logging and are within the reserve system (de Tores et al. 2004). Logging leads to local mortality including via increased feral cat predation (Morris et al. 2000; Wayne et al. 2000). In one logged forest block north-east of Manjimup, 12 of the 17 radio collared Western Ringtail Possums were dead within 20 months of logging (Burrows et al. 1993, 2002).

Felling in Jarrah forests have increased debris and ground fuel, which has resulted in more severe fire events over greater areas. Perup forest, which is situated at the less productive margin of the Jarrah forest, was not logged until late in the 20th century and avoided such catastrophic fire events (Wardell-Johnson et al. 2004; Wayne et al. 2006).

European Red Fox predation

Radio-tracking of translocated individuals has shown a high mortality due to European Red Fox predation (de Tores et al. 2004). Despite significant European Red Fox control programs, such as Operation Foxglove and the Western Shield fox baiting programs, the species is still the major cause of mortality (Burbidge & de Tores 1997; de Tores et al. 2004; Jones et al. 1994b). The local population at Collie River, Harvey River, Bunbury, Busselton and within Jarrah/Marri forest near Manjimup are at high risk of predation (de Tores et al. 2004).

Monitoring at Perup Nature Reserve, which has been baited for the European Red Fox since the 1970s, revealed Western Ringtail Possum population size increases during the 1980s (Wayne et al. 2006). This population, however, had declined to near extirpation by the late 2000s (Wayne et al. 2012 cited in Woinarski et al. 2014). Another study (de Tores et al. 2004) notes that there are no Western Shield monitoring sites where the Western Ringtail Possum has shown a response to European Red Fox control. The presence of Gastrolobium spp. at Perup Nature Reserve, a species which contains high levels of fluoroacetate (1080), which is toxic to introduced species, may explain the persistence of diverse marsupial populations at the site during the 1990s (Wardell-Johnson et al. 2004).

Cat predation

There are instances of Western Ringtail Possum translocation failing because of Cat predation (Woinarski et al. 2014). Common Ringtail Possums are highly represented in feral Cat diets in eastern Australia (Dickman 1996) and are a major predator of the Western Ringtail Possum (Woinarski et al. 2014). Cat predation also exposes the the species to toxoplasmosis infection (de Tores et al. 2008). In 1909, declines in Western Australian marsupials began before the arrival of the European Red Fox and were attributed the "constant raids of dogs and domestic cats" (Wardell-Johnson et al. 2004). 

Road kills

In one study, it was shown that more Western Ringtail Possum road kills occurred on stretches of road with forest on one side and rural land on the other, with fewer killed where vegetation was present on both sides of the road (Trimming et al. 2009).

Competition with the Common Brushtail Possum

Interspecies competition has been observed between the Western Ringtail Possum and the Common Brushtail Possum (Trichosurus vulpecula) (Jones et al. 1994b), with the latter known to evict the former from hollows in some instances (Jones 2000). There are instances of translocations of the Common Brushtail Possum from areas to minimise pressure on Western Ringtail Possums (Jones 2000), however, habitat partitioning is known to occur and the threat of competition for refuges was unlikely in the Jarrah forest (Jones 2000; Jones & Hillcox 1995; de Tores et al. 2004).

Actions undertaken

European Red Fox control is undertaken within State forest and conservation reserves where the species occurs (Woinarski et al. 2014). Fire management near urban and semi-urban coastal development has proved difficult and controversial, and regular fuel reduction is likely to reduce the quality of habitat (Woinarski et al. 2014). In urban environments at risk to development, the species is protected in situ through retention of sufficient habitat trees rather than translocating animals away from disturbance (Woinarski et al. 2014). A full list of actions undertaken are available in Department of Parks and Wildlife (2014).

Management stratagies, at least in local settings, can be used to overcome drought impacts (Shedley & Williams 2014). At one site during drought, mature Peppermint Trees were thinned and replanted, fertilised and watered, the number of young Western Ringtail Possums recovered to pre-thinning levels, despite an overall reduction of adults (Jones cited in Shedley & Williams 2014).

Priority recovery actions

Woinarski and colleagues (2014) identify the following high priority research activities:

  • maintain and enhance European Red Fox and Cat control in conservation estate
  • control feral Cats at key subpopulations
  • develop a better approach to minimising severe impacts of urban development
  • mange fire regimes to benefit this species
  • implement forestry guidelines that ensure maintenance of viable subpopulations
  • monitor at selected sites so conservation status can be assessed on an ongoing basis
  • assist landowners to conserve the Western Ringtail Possum on their land.

Woinarski and colleagues (2014) identify the following high priority research activities:

  • collate and analyse existing data to better assess change in extent of occurrence, area of occupancy, population size and trends
  • undertake stratified sampling to assess size of subpopulations
  • develop broad-scale, targeted feral Cat eradication technology

The southern Swan Coastal Plain region is an important area for Western Ringtail Possum, and as such, particular care should be taken when planning development in this region. Proposed actions should be designed to retain and improve habitat areas and corridors; retain and protect Peppermint Trees with a diameter at breast height of greater than 10 cm; recreate habitat areas and corridors; plant and nurture new Peppermint Trees to replace damaged or removed trees, or to enhance existing habitat; and where fences are required, construct to a height of at least 210 cm to reduce the risk of dog attack (DEWHA 2009). Translocation does not reduce the impact of an action and is therefore not a mitigation measure (DEWHA 2009). The Significant impact guidelines for the vulnerable western ringtail possum in the southern Swan Coastal Plain (DEWHA 2009) should help state and local planning authorities, Commonwealth assessment officers and residents considering development in this region to take into account:

  • the significance of the Bunbury to Dunsborough coastal plain area to the conservation of the Western Ringtail Possum
  • the extensive and continued clearing pressure that operates in this zone
  • the high number of EPBC referrals and "controlled action" developments for a range of federally listed threatened species and communities which have occurred since 2000.

Actions occurring within habitat critical to survival that result in any of the following may have a significant impact on the Western Ringtail Possum (DPaW 2014):

  • clearing/loss of habitat
  • decrease in canopy continuity and canopy condition in habitat
  • decrease in food availability
  • decrease in refuge site availability
  • increased likelihood of predation beyond natural levels
  • increased likelihood of competition with other fauna beyond natural levels
  • reduced ability to disperse.

Amendement No. 146 of the Shire of Busselton District Town Planning Scheme No. 20 seeks to regulate the clearing of existing individual or groups of Peppermint Tree habitat not protected under existing legislation, offer incentives to encourage retention of existing habitat and provide a system for offset plantings where clearing is approved (Shire of Busselton 2012 cited in Shedley & Williams 2014).

Major studies on the Western Ringtail Possum have been undertaken on the following topics:

  • Distribution, habitat and ecology (Jones et al. 1994a, 1994b; Shedley & Williams 2014; Wayne 2005; Wayne et al. 2005c, 2006)
  • Biology of captive population (Elis & Jones 1992)
  • Local surveys (de Tores & Rosier 1997), compilation of local surveys (Shedley & Williams 2014)
  • Survey methods (de Tores & Elscot 2010; Wayne et al. 2005a, 2005b)
  • Recovery studies (de Tores et al. 2004)
  • Translocation monitoring (Millen 1997).

Management documents relevant to the Western Ringtail Possum are available at the start of the profile. Another management document relevant to the species includes the management strategy for the Harvey River population (Ninox Wildlife Consulting 1999a, 1999b).

The following table lists known and perceived threats to this species. Threats are based on the International Union for Conservation of Nature and Natural Resources (IUCN) threat classification version 1.1.

Threat Class Threatening Species References
Ecosystem/Community Stresses:Ecosystem Degradation:Decline in habitat quality Pseudocheirus occidentalis in Species Profile and Threats (SPRAT) database (Department of the Environment and Heritage, 2006vc) [Internet].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or predation Vulpes vulpes (Red Fox, Fox) Pseudocheirus occidentalis in Species Profile and Threats (SPRAT) database (Department of the Environment and Heritage, 2006vc) [Internet].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or predation Felis catus (Cat, House Cat, Domestic Cat) Pseudocheirus occidentalis in Species Profile and Threats (SPRAT) database (Department of the Environment and Heritage, 2006vc) [Internet].
Invasive and Other Problematic Species and Genes:Invasive Non-Native/Alien Species:Competition and/or predation Canis lupus familiaris (Domestic Dog) Pseudocheirus occidentalis in Species Profile and Threats (SPRAT) database (Department of the Environment and Heritage, 2006vc) [Internet].
Species Stresses:Indirect Species Effects:Low numbers of individuals Pseudocheirus occidentalis in Species Profile and Threats (SPRAT) database (Department of the Environment and Heritage, 2006vc) [Internet].

Baverstock, P.R., M. Krieg, J. Birrell & G.M. Mckay (1990). Albumin immunologic relationships of Australian marsupials. II. The Pseudocheiridae. Australian Journal of Zoology. 38:519-526.

Burbidge, A.A. & de Tores (1997). Western Ringtail Possum (Pseudocheirus occidentalis) Interim Recovery Plan 1997-1999. Perth: unpublished draft report prepared for the Department of Conservation and Land Management.

Burrows, N., B. Ward & R. Cranfeld (2002). Short term impacts of logging on understorey vegetation in a Jarrah forest. Australian Forestry. 65:47-58.

Burrows, N., G. Friend, K. Morris, G. Stoneman, G. Wardell-Johnson & M. Williams (1993). A proposed integrated study of the effects of timber harvesting on the Jarrah forest ecosystem. Perth: Department of Conservation and Land Management.

de Tores P.J. & S. Elscot (2010). Estimating the population size of a threatened arboreal marsupial: use of distance sampling to dispense with ad hoc survey techniques. Wildlife Research. 37:512-23.

de Tores, P. & S.R. Rosier (1997). Harvey Basin allocation plan: Western Ringtail Possum survey. Perth: Unpublished report prepared for the Waters and Rivers Commission.

de Tores, P., M.W. Hayward & S.R. Rosier (2004). The Western Ringtail Possum, Pseudocheirus occidentalis and the Quokka, Setonix brachyurus, case studies: Western Shield review - February 2003. Conservation Science Western Australia. 5:235-257.

de Tores, P., S. Rosier, J. Jackson, J. Clarke & L. Aravidis (2008). Working to conserve the western ringtail possum. Landscope. 25(4):54-61.

Department of Environment and Conservation (Western Australia) (DEC) (2007). Records held in DEC's Threatened Fauna Database and rare fauna files. Perth: Department of Environment and Conservation.

Department of Parks and Wildlife (DPaW) (2014a). Ringtail Possum (Pseudocheirus occidentalis) Recovery Plan. [Online]. Wildlife Management Program No. 58. Department of Parks and Wildlife, Perth, WA. Available from: http://www.dpaw.wa.gov.au/plants-and-animals/threatened-species-and-communities/197-approved-recovery-plans.

Department of Sustainability, Environment, Water, Population and Communities (DSEWPaC) (2011j). Survey guidelines for Australia's threatened mammals. EPBC Act survey guidelines 6.5. [Online]. EPBC Act policy statement: Canberra, ACT: DSEWPAC. Available from: http://www.environment.gov.au/epbc/publications/threatened-mammals.html.

Department of the Environment, Water, Heritage and the Arts (DEWHA) (2009). EPBC Act Policy Statement 3.10: Significant impact guidelines for the vulnerable western ringtail possum (Pseudocheirus occidentalis) in the southern Swan Coastal Plain, Western Australia. [Online]. Canberra, ACT: DEWHA. Available from: http://www.environment.gov.au/epbc/publications/western-ringtail-possum.html.

Elis, M. & B. Jones (1992). Observations of captive and wild Western Ringtail Possums Pseudocheiruus occidentalis. Western Australian Naturalist. 19:1-10.

Jones, B. (2000). A Western Ringtail Possum study for the Stirling-Harvey redevelopment scheme: an unpublished report on the conservation status and future management requirements of the possum population in the Harvey River valley. Perth: Water Corporation.

Jones, B. & S. Hillcox (1995). A survey of the possums Trichosurus vulpecula and Pseudocheirus occidentalis and their habitats in forest at Ludlow, Western Australia. Western Australian Naturalist. 20:139-150.

Jones, B.A., R.A. How & D.J. Kitchener (1994a). A field study of Pseudocheirus occidentalis (Marsupialia : Petauridae). I. distribution and habitat. Wildlife Research. 21:175-187.

Jones, B.A., R.A. How & D.J. Kitchener (1994b). A field study of Pseudocheirus occidentalis (Marsupialia: Petauridae). II. population studies. Wildlife Research. 21:189-201.

Kitchener, D.J. & E. Vicker (1981). Catalogue of Modern Mammals in the Western Australian Museum 1895 to 1981. Page(s) 184. WA Museum: Perth.

Maxwell, S., A.A. Burbidge & K. Morris (1996). The 1996 Action Plan for Australian Marsupials and Monotremes. [Online]. Wildlife Australia, Environment Australia. Available from: http://www.environment.gov.au/resource/action-plan-australian-marsupials-and-monotremes.

McFarlane, D.J. (2005). Context report on south west water resources for Expert Panel examining Kimberley water supply options: Client report to Western Australian Government. Canberra: CSIRO - Water for a Healthy Country National Research Flagship.

McKay, G.M. (1984). Cytogenetic relationships of possums and gliders. In: Smith, P.A. & I.D. Hume, eds. Possums and Gliders. Page(s) 9-16. Sydney: Australian Mammal Society and Surrey Beatty & Sons Pty Ltd.

Millen, N. (1997). Translocation of the Western Ringtail Possum (Pseudocheirus occidentalis) to the Northern Jarrah Forest of south-west Western Australia: analysis of habitat use; home range; and survivorship. Hons. Thesis. Curtin University of Technology.

Murray, J.D., G.B. Sharman, G.M. Mckay & J.H. Calaby (1980). Karyotypes, constitutive heterochromatin and taxonomy of ringtail opossums of the genus Pseudocheirus (Marsupialia: Petauridae). Cytogenetics and Cell Genetics. 27:73-81.

Ninox Wildlife Consulting (1999a). Stirling-Harvey Redevelopment Scheme: Part 1: Stirling-Harvey pipeline and interim management strategy for the Western Ringtail Possum. Perth: unpublished report for the Water Corporation.

Ninox Wildlife Consulting (1999b). Stirling-Harvey Redevelopment Scheme: Part 2: Harvey Reservoir fauna management plan and management strategy for Western Ringtail Possum. Perth: unpublished report for the Water Corporation.

Ride, W.D.L. (1970). Native Mammals of Australia. Melbourne: Oxford University Press.

Shedley, E. & K. Williams (2014). An assessment of habitat for western ringtail possum (Pseudocheirus occidentalis) on the southern Swan Coastal Plain. Unpublished report for the Department of Parks and Wildlife, Bunbury, Western Australia.

Trimming, E.M., B.K. Chambers, D. Grillo, P.J. de Tores & R. Bencini (2009). Road Kills of the Western Ringtail Possum (Psedocheirus occidentalis) Occur at Specific Hotspots. In: Semi-Centenary and 55th Meeting in Perth July 5-9, 2009 Scientific Program.

Van Dyck, S. & R. Strahan (2008). The Mammals of Australia, Third Edition. Page(s) 880. Sydney: Reed New Holland.

Wardell-Johnson, G., M. Calver, D. Saunders, S. Conroy, B. & B. Jones (2004). Why the integration of demographic and site-based studies of disturbance is essential for the conservation of jarrah forest fauna. In: Lunney, D., ed. Conservation of Australia's forest fauna, 2nd edition. Page(s) 394-417. Mosman: Royal Zoological Society of New South Wales.

Wayne, A. (2005). The ecology of the koomal (Trichosurus vulpecula hypoleucus) and the ngwayir (Pseudocheirus occidentalis) in the Jarrah forests of south-western Australia. Ph.D. Thesis. Canberra: Centre for Resource and Environmental Studies, Australian National University.

Wayne, A., C. Ward, J. Rooney & I. Wheeler (2000). The immediate impacts of timber harvesting and associated activities on the ngwayir (Pseudocheirus occidentalis) in the jarrah forest of Kingston State Forest Block: Progress report. Manjimup: Department of Conservation and Land Management.

Wayne, A.F., A. Cowling, C.G. Ward, J.F. Rooney, C.V. Vellios, D.B. Lindenmayer & C.F. Donnelly (2005a). A comparison of survey methods for arboreal possums in Jarrah forest, Western Australia. WIldlife Research. 32:701-714.

Wayne, A.F., A. Cowling, D.B. Lindenmayer, C.G. Ward, C.V. Vellios & C.F. Donnelly (2006). The abundance of a threatened arboreal marsupial in relation to anthropogenic disturbances at local and landscape scales in Mediterranean-type forests in southwestern Australia. Biological Conservation. 127:463-476.

Wayne, A.F., A. Cowling, J.F. Rooney, Ward.C.G., Wheeler, B.I., D.B. Lindenmayer & C.F. Donnelly (2005b). Factors affecting the detection of possums by spotlighting in Western Australia. Wildlife Research. 32:689-700.

Wayne, A.F., C.G. Ward, J.F. Rooney, C.V. Vellios & D.B. Lindenmayer (2005c). The life history of Pseudocheirus occidentalis (Pseudocheiridae) in the Jarrah forests of south western Australia. Australian Journal of Zoology. 53:265-278.

Woinarski, J., A. Burbidge & P. Harrison (2014). The Action Plan for Australian Mammals 2012. CSIRO Publishing, Victoria, Australia.

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This database is designed to provide statutory, biological and ecological information on species and ecological communities, migratory species, marine species, and species and species products subject to international trade and commercial use protected under the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act). It has been compiled from a range of sources including listing advice, recovery plans, published literature and individual experts. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. Individuals and organisations should consider all the available information, including that available from other sources, in deciding whether there is a need to make a referral or apply for a permit or exemption under the EPBC Act.

Citation: Department of the Environment (2014). Pseudocheirus occidentalis in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Wed, 17 Sep 2014 06:04:59 +1000.