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
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, 2014) [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 weighing up to 1.3 kg and approximately 40 cm in body length. Its fur is dark brown above with cream to grey fur underneath. Its ears are short and rounded compared 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).

The Western Ringtail Possum has a patchy distribution from the Collie River to Two Peoples Bay in Western Australia, occurring most commonly in coastal or near coastal forest that includes Peppermint Tree (Agonis flexuosa) as a major component. The most inland population occurs at Perup and this is the only known population living in forest that does not contain Peppermint Tree. The species has been recorded as far north as an isolated reserve in Boddington (DEC 2007) and as far east as Eucla. This species is considered to have a fragmented distribution. In the town of Busselton, some urban or developed areas support viable populations. Other populations in urban or semi-urban areas occur at Augusta and Albany (Jones et al. 1994b). There are also unconfirmed reports around Augusta and at Molloy Island (DEC 2007).

Local extinction has been extensive in the inland and northern parts of the original range (as it was known in 1900). Local decline has been patchy and has occurred in most decades (1900–1989) in different parts of the original range. This species was lost from all drainage systems between the Avon and Harvey river systems during the 20th century (Jones 2000). Research by Wayne and colleagues (2006) indicates that high value habitat for the Western Ringtail Possum has been selectively cleared for agriculture, owing to the area's fertile and productive nature. Habitat loss is likely to be a major cause of the modern decline of this species. Western Ringtail Possums feed and move preferentially in the canopy, limiting their ability to disperse and recolonise areas across fragmented landscapes (DEC 2007).

Using post-1995 records the extent of occurrence of the Western Ringtail Possum in 2007 was estimated to be 7155 km². This was estimated by constructing minimum convex polygons around distinctly separate records in south-west Western Australia. In 2007, the area of occupancy for the Western Ringtail Possum was estimated to be 3700 km². The records used for analysis were obtained from the following sources (DEC 2007):

  • the Threatened and Priority Fauna Database (Western Australian Department of Environment and Conservation) which contains records from a variety of sources and includes sighting records, roadkills and museum specimens
  • the Western Australian Museum database
  • various Western Australia Department of Environment and Conservation District offices
  • consultation with private researchers
  • published records.

Western Ringtail Possums are known from the following locations in the south-west of Western Australia (DEC 2007):

Population Location
1 Inland areas between south of Harvey to Preston
2 A sparse population extending between south of Bunbury to Yalingup
3 Isolated records from Leeuwin-Naturaliste National Park
4 The southern forest area between Bridgetown to Northcliff
5 Isolated records between Walpole to east of Denmark
6 West Cape Howe to Mount Manypeaks
7 Isolated records from Porongurup National Park

In accordance with the (draft) interim recovery plan (Burbidge & De Torres 1997), populations have been translocated to the following locations:

  • Leschenault Peninsula Conservation Park
  • Yalgorup National Park (White Hill and Preston Beach)
  • Lane Poole Reserve and Keats Forest Block (within the northern Jarrah forest south-east of Dwellingup)
  • Karakamia Sanctuary, Chidlow
  • Locke Nature Reserve, as a pilot study in translocation.

Translocation is not always the preferred option as a management tool (de Tores et al. 2008). In addition, translocation success of Western Ringtail Possums at these locations is yet to be determined (de Tores et al. 2004; DEC 2007). However, tentative results suggest viable populations have been established at Yalgorup National Park and Lane Poole Nature Reserve (de Tores et al. 2008). The release study was in conjunction with a fox baiting control program and involved 142 possums caught and relocated from six development sites between July 1995 and September 2001. Western Ringtail Possums have also been translocated to Crampton Nature Reserve in the past (DEC 2007).

Western Ringtail Possums are held at the following locations, where they are kept by private carers or used for educational purposes (DEC 2007):

  • Kooikuna Fauna Cave, Mundaring
  • Fauna Rehabilitation Foundation, Malaga
  • Perth Zoo.

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 populations 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 populations could be counted, estimates of local populations ranged from seven to 104 individuals. As these numbers are generally very low, and given the high level of predation by foxes (Jones et al. 1994b), such populations cannot be considered secure.

Population numbers are unknown (there are no published estimates) and reaching a statistically accurate estimate is very difficult as the species occurs in fragmented and scattered subpopulations, and is difficult to trap (DEC 2007). Overall, the population trend for the species is declining (DEC 2007).

The following table includes estimated population sizes for the Western Ringtail Possum within the seven broad geographic locations in which it is known (DEC 2007):

Population Location Estimated Population Size Land tenure
1 Peppermint Park Present in low numbers Private property
1 Harvey River Basin Population considered to be at risk, estimate range 7–104 Water Corporation Estate/Nature Reserve/State Forest
2 Leschenault Peninsula Conservation Park Population considered to be at risk Conservation Park
  Ludlow Forest region, Capel 274 Western Ringtail Possums sighted in 1995 State Forest
2 Abba River region Busselton Population considered to be at risk Various
2 Locke Estate Stable Nature Reserve
2 Bussel Highway 70–90 individuals spotted in a stand of 700 Peppermint Trees Freehold
Near 3 East Augusta   National Park
Near 3 Ellensbrook   Various
4 Lower Collie River region Population considered to be at risk Unknown
4 Perup Forest Block, Manjimup High density population detected from ad hoc spotlighting State Forest
4 Kingston Block, Manjimup Population considered to be at risk State Forest
4 Greater Kingston area Population considered to be at risk State Forest
5 William Bay National Park Unknown National Park
5 Wilsons Inlet Present Various
6 West Cape Howe National Park Known to be present National Park
6 Gull Rock National Park Present National Park
6 Waychinicup - Mt Manypeaks, Normans Inlet Regularly sighted National Park
6 Angove Water Reserve Regularly sighted. Evidence of recolonisation of an area burnt in 2000 Water reserve
6 Albany area Present Various
6 Two Peoples Bay Nature Reserve Present Nature Reserve
7 Porongorup National Park Present National Park

To date the following population trends have been observed (DEC 2007):

Population Status
1 Declining
2 Declining
3 Stable
4 Stable-Declining
5 Declining
6 Stable-Declining
7 Status unknown since 2007 wildfires

The generation length of Western Ringtail Possum is two to three years (DEC 2007). Given the low breeding capacity, relatively short lifespan and susceptibility to predation of this species, all known populations are considered essential for the species recovery and long-term survival (DEC 2007).

The southern Swan Coastal Plain (population 2) is of particular importance for the Western Ringtail Possum, as it: supports the largest and most dense population; provides the greatest potential for recruits to adjoining areas; supports dense and productive Peppermnt Tree stands; and provides habitat where the Brushtail Possum (Trichosurus vulpecula) does not co-occur, and therefore does not compete for resources (DEWHA 2009).

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).

The Western Ringtail Possum is usually associated with stands of myrtaceous trees growing near swamps, water courses or floodplains (Jones 2000). The main determinant of suitable habitat is the presence of Peppermint Tree (Agonis flexuosa), either as the dominant tree (e.g. coastal forest (Busselton) or riverine stands (Harvey River)) or as an understorey component of eucalypt forest or woodland (e.g. Tuart (Eucalyptus gomphocephala) forest, Jarrah (Eucalyptus marginata) forest or Jarrah-Marri (Corymbia calophylla) forest (near Collie)) (Jones et al. 1994a; de Tores et al. 2004). The species has only been recorded at one site, near Perup, where no Peppermint Trees were present (Jones et al. 1994a). At this site, the Heart-leaf Poison Bush (Gastolobium bilobum) is a common understorey species.

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).

Habitat parameters affecting the distribution of the Western Ringtail Possum are well known (e.g. DEWHA 2009; Jones & Hilcox 1995). Topographic low points provide cooler conditions that are favoured by this species (de Tores et al. 2004). In an assessment of habitat suitability for the species, 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 (Agonis flexuosa)
  • 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 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 populations, 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. 1994). The young are weaned at six to eight months and disperse at 8-12 months (How 1978 cited in Wayne et al. 2005c). Both captive populations and wild populations in the Jarrah forest are documented as breeding at 12 months (Ellis & Jones 1992; Wayne et al. 2005c). 

Wayne and colleagues (2005c) speculate that female sex ratio bias indicates expanding population 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 this species is absent, the diet consists mostly of Marri and Jarrah leaves (Jones et al. 1994b). Although arboreal, the species is known to descend to the ground when foraging (de Tores & Rosier 1997).

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 to 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 some 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 Jarrah forest populations compared to near coastal populations 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 is nocturnal and not usually seen during the day. Its presence can be determined by searching for faecal pellets and dreys, by spotlighting at night and by cage trapping (DEC 2007).

For spotlighting and faecal pellet survey techniques, de Tores and Rosier (1997) note that detection is enhanced by increased population density. At low population density the species may remain undetected.

Spotlighting at night, either with handheld torches or with vehicle headlights, is the most non-invasive technique, as it does not require capturing the animal, so disturbance is limited. In the Jarrah forests, Wayne and colleagues (2005a) found repeated spotlighting provides similar or better detection rates than extensive trapping and requires substantially less effort. Spotlighting is best conducted early in the evening. Wayne and colleagues (2005b) highlight that despite extensive experience there may be skill differences between observers which will affect spotlight detection results and that spotlight detection rates are also likely to be sensitive to the survey speed (where this is conducted in vehicles). Spotlighting can be improved by selecting optimal procedural and environmental conditions that influence detection rates, such as season and weather (Wayne et al. 2005b). The same study found that the number of Western Ringtail Possums seen whilst spotlighting was inversely related to the amount of rain recorded on the day of the survey.

The presence of Western Ringtail Possums can also be determined by searching for their distinctive faecal pellets and their dreys. Dreys (constructed nests) are made from fine to medium-sized material collected from overstorey and understorey vegetation. Dreys vary in their degree of construction, and range from flimsy and 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. In the lower Collie River valley, dreys are rare and the use of tree hollows is more common. 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). Although they are not easily caught in traps, 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.

Clearing and fragmentation of habitat

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 concentrated on land adjacent to waterways. These are areas 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 and tourist 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 forests occurs are outside of managed reserves.

European red fox (Vulpes vulpes) predation

European Red Fox predation is one of the main threats to the Western Ringtail Possum (de Tores et al. 2004; Wayne 2005; Jones et al. 1994b), especially as it is predator naive and highly susceptible to infection (de Tores et al. 2008). Populations at high risk have been identified at Collie River, Harvey River, Bunbury, Busselton and within Jarrah/Marri forest near Manjimup (de Tores et al. 2004). Despite significant fox control programs, Operation Foxglove and Western Shield fox baiting programs, foxes are still the major cause of mortality (BSD consultant 2003; Burbidge & de Tores 1997; de Tores et al. 2004; Jones et al. 1994b).

Change in forest structure through logging or clearing have also 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 by both cats and foxes (Burbidge & de Tores 1997; Jones et al. 1994b).

Monitoring at Perup Nature Reserve, which has been baited for foxes since the 1970s, had Western Ringtail Possum population increases during the 1980s (Wayne et al. 2006). The presence of Gastrolobium spp. at the site, which contains high levels of fluoroacetate (1080), which is toxic to introduced species, may also explain the persistence of diverse marsupial populations at Perup Nature Reserve (Wardell-Johnson et al. 2004). However, 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 fox control. 

Cat (Felis catus) predation

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). Cat predation also exposes the Western Ringtail Possum to toxoplasmosis infection (de Tores et al. 2008). Successful fox baiting programs may switch cats, pythons 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 fox control (de Tores et al. 2008).

Timber harvesting

Timber harvesting and burning operations can also threaten the Western Ringtail Possum: such actions result in loss of habitat, habitat fragmentation, loss of nest trees and refuges, loss of canopy and population displacement. This has been an issue within the Manjimup populations in particular and in Dardanup Shire (DEC 2007; de Tores et al. 2004; Wayne et al. 2000). However, many of the known Western Ringtail Possum populations are outside areas available for logging and are within the reserve system (de Tores et al. 2004) and so are not currently at risk; nor will they be in the future.

To understand the impacts of logging within the Jarrah forests, an experimental study was conducted in Kingston Block, 25 km north-east of Manjimup (Burrows et al. 1993). The results indicated a severe decline in Western Ringtail Possums, with 12 of the 17 radio collared Western Ringtail Possums all dead within 20 months of logging (Burrows et al. 2002). These results were consistent with a later study by Wayne and colleagues (2006), who found that the abundance of Western Ringtail Possums was greater in predominantly unlogged forests, and in forests which were logged in the 1960s when logging practices were historically less intense.

As felling operations in Jarrah forests have increased, this has led to increased debris and ground fuel, which has in turn resulted in more severe fires over greater areas. This observation is supported by Wayne and colleagues (2006) research into the Perup forest, which is situated at the less productive margin of the Jarrah forest, and was not logged until late in the 20th century (Wardell-Johnson et al. 2004). By this reasoning, Perup suffered less from the impacts of fire which has been an important factor in it retaining its diverse marsupial assemblage (Wardell-Johnson et al. 2004).

Altered fire regimes
Fires and their intensity, extent, frequency and seasonality differed prior to European settlement and this is well documented (Wardell-Johnson et al. 2004). The three ways in which fire can have a negative impact on Western Ringtail Possums (Wayne et al. 2006) are:

  • by reducing the availability of food resources
  • through the loss of shelter sites
  • by directly or indirectly killing individuals.

In a historical context, the low intensity patch burning practiced by Nuyngar peoples in Jarrah forest "would have tended to 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). This is important because if an intense fire is extensive, Western Ringtail Possums may starve during the three to four months that it takes for sufficient new growth to provide a replacement food source.

Road kills
Road traffic is a current threat to Western Ringtail Possum populations, and may contribute to the decline in abundance of the species near roads. There are occasional reports of Western Ringtail Possums through the collection of roadkills. In the database used for this work, 12% of reports post-1995 were road kills, which could have resulted from populations in isolated and thin remnant roadside vegetation. The core of large reserves would be least affected (DEC 2007). In one study, it was shown that more 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 (Trimmin et al. 2009).

Effects of drought
Depending upon the distance of the population to water sources, and whether the water source is perennial or not (de Tores et al. 2004), Western Ringtail Possums may succumb to the effects of localised or generalised drought. Sensitivity to heat and drought-induced stress has been observed in Western Ringtail Possums (Jones et al., 1994b). Wayne and colleagues (2005c) note that hot summer droughts may contribute to the stress and poorer condition of Western Ringtail Possums in the Jarrah forest.

Disease
Shortridge (1909 cited in Wardell-Johnson et al. 2004) ascribed the early disappearance of native animals to epidemics, among other causes. There are anecdotal records of spectacular declines in native mammal species attributed to disease from the 1880s until 1920 (Abbott 2001). It is possible that, with the introduction of European animals such as sheep, horses, rats, mice, cats and dogs, fleas and ticks have appeared which spread disease such as toxoplasma, to which native animals are susceptible (Abbott 2001). This species is particularly poor at mounting immune response to infection, a problem that has heightened with greater risk of disease due to human disturbance and exposure to exotic species and pathogens (de Tores et al. 2008).

Competition with Brushtail Possums
Interspecies competition has been observed between Western Ringtail Possums and Common Brushtail Possums (Trichosurus vulpecula) (Jones et al. 1994b). Brushtails that are intent on using a particular hollow can evict Western Ringtail Possums (Jones 2000), thus creating population pressure. There are instances of translocations of Brushtail Possums from areas of co-habitation with Ringtails to minimise population pressure on Western Ringtail Possums (Jones 2000). However, de Tores and colleagues (2004) examined habitat use of Western Ringtail Possums and Common Brushtails and, like similar studies (Jones 2000; Jones & Hillcox 1995), found habitat partitioning to occur. They concluded that the threat of competition for refuges was unlikely in the Jarrah forests.

Climate change
South-west Western Australia is one of the most water challenged parts of the country, experiencing Australia's highest rates of climate change and dryland salinity amid rapid population growth and associated development. Between 1975 and 1996 rainfall decreased by 14% and runoff into Perth dams decreased by 48%. Since 1997, rainfall decline has been 21% and runoff has been 64% less than the long term average. In the four years since 2001, rainfall was 36% less and runoff 88% less (McFarlane 2005). Predicted climate change will probably result in elevated threat probabilities. Modelling of potential impacts on specific Australian taxa using bioclimatic analysis programs such as BIOCLIM consistently predicts contraction and/or fragmentation of species' current ranges (Arnold 1988; Brereton et al. 1995). Species which have very specific habitat requirements and a poor ability to migrate have lost large areas of habitat because of clearing etc; animals with a small genetic base are all listed as being at certain risk due to climate change. Brereton and colleagues (1995) list the Western Ringtail Possum among those animals.

Reproduction
Both Jones and colleagues (1994b) and Wayne and colleagues (2005c) highlight the survival implications of anything less than 100% survivorship of offspring to maturity, given an annual fecundity rate of one young per mature female and a relatively short life span. To maintain population size a female needs a minimum of two successful reproductive seasons and 100% offspring survival to maturity. Anything that negates this may threaten the viability of the population (Wayne et al. 2005c).

Priority recovery actions
A number of recovery actions are suggested for the recovery of the Western Ringtail Possum (DEWR 2007bc; Maxwell et al. 1996; Wayne 2005):

  • strategically implement fox and cat control
  • determine suitable management regimes and implement clear conservation objectives
  • retain current population distribution and abundance
  • increase abundance (and range) by reintroduction to suitable large conservation reserves
  • maintain diversity and minimise disturbance to habitat (landscape)
  • recreate, retain and improve habitat characteristics, including corridors
  • retain and plant Peppertmint Trees
  • restrain domestic animals in residential areas
  • where fencing is required, ensure that it is 210 cm to reduce the risk of dog attack
  • investigate strategies for reducing roadkill.

Policy statement for the southern Swan Coastal Plain
The Australian government, in consultation with the Western Australia Deparment of Environment and Conservation, has developed a policy statement for the Western Ringtail Possum in the southern Swan Coastal Plain region (DEWHA 2009). The purpose of this policy is to assist in determining whether proposed actions on the southern Swan Coastal Plain are likely to have a significant impact on the species. The document identifies and maps important areas (core habitat, supporting habitat and primary corridors) that form key habitat for the conservation of the Western Ringtail Possum within the southern Swan Coastal Plain region. The key aims of this policy statement are to:

  • protect key remnant habitat patches
  • ensure that the possum can persist in the Busselton urban area
  • expand habitat
  • maintain or create habitat connections that allow strong movement of individuals (in order to maintain genetic representation between local populations.

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). The policy also reinforces the department's position that translocation does not reduce the impact of an action and is therefore not a mitigation measure (DEWHA 2009). This policy statement (DEWHA 2009) should help state and local planning authorities, Commonwealth assessment officers and residents considering development in this region 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 over the last five years.

Draft interim recovery plan
The species is currently managed in accordance with the draft Interim Recovery Plan (IRP) (Burbidge & de Tores 1997). In accordance with the IRP, populations have been translocated to Leschenault Peninsula Conservation Park, Yalgorup National Park, the northern Jarrah forest south-east of Dwellingup and Karakamia sanctuary near Chidlow. A national recovery plan is currently being prepared and will aim at increasing the understanding of the species, protecting the species and recovering the species (DEWHA 2009).

Other management strategies
In 1999, the Water Corporation developed a management strategy specific to the Harvey River population of Western Ringtail Possums (Ninox Wildlife Consulting 1999a). In 2000, the Water Corporation planted 35 ha of Peppermint Trees which, when mature, would provide habitat suitable for the Western Ringtail Possum population in the future (Jones 2000).

Type Title Author Publication Volume Date
Journal Observations of captive and wild western ringtail possums Pseudocheiruus occidentalis. Elis, M. and B. Jones Western Australian Naturalist 19:1–10 1992
Report Harvey Basin Allocation Plan: Western Ringtail Possum Survey. Report on the western ringtail possum survey within part of the inundation area of proposed Harvey Dam. de Tores and Rosier Report for the Waters and Rivers Commission   October 1997
Journal The Western Ringtail Possum, Pseudocheirus occidentalis and the Quokka, Setonix brachyurus, case studies: Western Shield review - February 2003 de Tores, M.W. Hayward and S.R. Rosier Conservation Science Western Australia 5:235–257 2004
Book Western Ringtail Possums Pseudocheirus occidentalis (Thomas 1888) Jones, B. In: Strahan, R (ed.) The mammals of Australia. Australian Museum/ Reed New Holland Publishers Pty Ltd   1998
Journal A field study of Pseudocheirus occidentalis (Marsupialia: Petauridae) I. Distribution and Habitat Jones, B.A., R.A. How and D.L. Kitchener Wildlife Research 21:175–187

1994
Journal A field study of Pseudocheirus occidentalis (Marsupialia: Petauridae) II. Population Studies Jones, B.A., R.A. How and D.L. Kitchener Wildlife Research 21:189–201 1994
Honours Thesis 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. Millen, N. Curtin University of Technology, Perth, Western Australia   1997
PhD thesis The ecology of the koomal (Trichosurus vulpecula hypoleucus) and the ngwayir (Pseudocheirus occidentalis) in the jarrah forests of south-Western Australia Wayne, A. Ph.D. Centre for Resource and Environmental Studies, Australian National University, Canberra 280pp 2005
Journal A comparison of survey methods for arboreal possums in Jarrah forest, Western Australia. Wayne A.F., A. Cowling, C.G. Ward, J.F. Rooney, C.V. Vellios, D.B. Lindenmayer and C.F. Donnelly Wildlife Research 32:701–714 2005
Journal The life history of Pseudocheirus occidentalis (Pseudocheiridae) in the Jarrah Forests of South Western Australia. Wayne, A.F., C.G. Ward, J.F. Rooney, C.V. Vellios and D.B. Lindenmayer Australian Journal of Zoology 53:265–278. 2005
Journal Factors affecting the detection of possums by spotlighting in Western Australia. Wayne, A.F., A. Cowling, J.F. Rooney, C.G. Ward, B.I. Wheeler, D.B. Lindenmayer and C.F. Donnelly Wildlife Research 32:689–700 2005
Journal The abundance of a threatened arboreal marsupial in relation to anthropogenic disturbance at local and landscape scales in Mediterranean-type forests in south-western Australia Wayne, A.F., A. Cowling, D.B. Lindenmayer, C.G. Ward, C.V. Vellios, C.F. Donnelly and M.C. Calver Biological Conservation 127:463–476 2006

A policy statement for the Western Ringtail Possum in the southern Swan Coastal Plain region is available (DEWHA 2009). A draft interim recovery plan was prepared for the Western Ringtail Possum in 1997 (Burbidge & de Torres 1997).

A management strategy for the Harvey River Western Ringtail Possum population was prepared by the Water Corporation in 1999 for the Harvey River population (Ninox Wildlife Consulting 1999a, 1999b).

Amendement No. 146 osf 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 and habitat of existing habitat and provide a system for offset plantings where clearing is approved (Shire of Busselton 2012 cited in Shedley & Williams 2014).

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].

Abbott, I. (2001). The Bilby Macrotis lagotis (Marsupialia: Peramelidae) in south-western Australia: original range limits, subsequent decline, and presumed regional extinction. Records of the Western Australian Museum. 20:271-305.

Arnold, G.W. (1988). Possible effects of climate change on wildlife in Western Australia. In: Pearman, G.I., ed. Greenhouse: Planning for Climate Change. Page(s) 375-38. Melbourne: CSIRO Division of Atmospheric Research.

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.

Brereton, R., S. Bennett & I. Mansergh (1995). Enhanced greenhouse climate change and its potential effect on selected fauna of south-eastern Australia: A trend analysis. Biological Conservation. 72:339-354.

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.

Burbidge, A.A., A.N. Start, K.D. Morris & R. Armstrong (1995). Western Shield - Bringing back our wildlife. Western Australia: Department of Conservation and Land Management.

Bureau of Meteorology (2007). Bureau of Meteorology records. Western Australia Climate Services Centre.

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.

Christensen, P., A. Annels, G. Liddelow & P. Skinner (1985). Vertebrate fauna in the southern forests of Western Australia: a survey. Forests Department, Western Australia, Bulletin. 94:1-109.

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 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 and Heritage (2006). Draft EPBC Act Policy Statement: Western Ringtail Possum (Pseudocheirus occidentalis) in the Southerrn Swan Coastal Plain region. Unpublished Internal Guideline; Department of Environment and Heritage.

Department of the Environment and Water Resources (DEWR) (2007bc). Western ringtail possum, Pseudocheirus occidentalis Threatened Species Day Fact Sheet. [Online]. Available from: http://www.environment.gov.au/biodiversity/threatened/publications/tsd07-w-ringtail-possum.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.

Strahan, R. (Ed.) (1998). The Mammals of Australia, Second Edition, rev. Sydney, NSW: Australian Museum and Reed New Holland.

Thomas, O. (1888). Catalogue of the Marsupialia and Monotremata in the collection of the British Museum (Natural History). London: Trustees of British Museum (Nat. History).

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.

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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 Mon, 14 Jul 2014 05:14:50 +1000.