Survey guidelines for Australia’s threatened non-flying mammals

Western ringtail possum

Pseudocheirus occidentalis

States and territories: Western Australia.

Regions: Its former distribution was considered to have covered much of the south-west of Western Australia, for example in the 1970s it was known to occur in wheatbelt reserves near Pingelly (de Tores 2008). However, it is currently confined to five regional locations (de Tores et al. 2004, 2008):

• 
  near-coastal area between Bunbury and Albany
  
• 
  the Swan Coastal Plain near Busselton and urban Busselton
  
• 
  a population 90 km inland in the Western River catchment area
  
• 
  within the Jarrah Eucalyptus marginata and Jarrah-Marri Corymbia calophylla forests near Collie
  
• 
  riverine stands of peppermint near the Harvey river east of Harvey.
  

Habitat: The habitat differs across the species’ known range. For example, it is closely associated with peppermint Agonis flexuosa dominated forest and woodland, with a tuart Eucalyptus gomphocephala canopy in some areas along the coast south of Bunbury, in peppermint forest in the Busselton area and in jarrah E. marginata, wandoo E. wandoo and marri forest in inland localities (de Tores 2008).

Habit: Arboreal.

Avg. body weight: 575 g (Jones 1995).

Activity pattern: Nocturnal.

Diet: Leaves of various trees depending on the location. Peppermint is common near the coast, whereas further inland jarrah and marri predominate (Jones 1995).

Breeding: Breeding can occur throughout the year but most births occur during late autumn to winter, with a lull during the summer (de Tores 2008). Young emerge from the pouch after three months but continue to suckle for another three to four months (Jones et al. 1994b).

Description

The western ringtail possum is one of two large possums in Western Australia, with overlap in distribution occurring between the western ringtail possum and the common brushtail possum Trichosurus vulpecula (Menkhorst & Knight 2001). The species’ range once occurred from Perth to Albany in south western Western Australia, but since 1990 its distribution and density within the range has declined, particularly away from the coast (de Tores 2008).

Across the species’ range it is known to shelter in dreys constructed from leaves in areas close to the coast, but at a distance beyond 4 kilometres from the coast individuals use tree hollows instead of dreys. The use of dreys is similar to the common ringtail possum Pseudocheirus peregrinus from eastern Australia. Within a home-range area (between 0.5–2.5 hectares depending on the location, with larger home-ranges recorded in eucalypt forests away from the coast), an individual western ringtail possum may use between three to eight nest sites (Jones 1995). The home-ranges of adjacent individuals overlap, but individuals spend most of their time alone (Jones et al. 1994b).

Although no national recovery plan currently exists for the western ringtail possum, recovery actions and significant impact thresholds are outlined in the EPBC Act Policy statement 3.10 (DEWHA 2008a) as well as its supporting background paper (DEWHA 2008b).

Survey methods

On the basis of previous surveys, the following survey techniques are recommended to detect the presence of the western ringtail possum in areas up to 5 hectares in size:

• 
  daytime searches for potential den sites in hollow-bearing trees (particularly at sites greater than 4 kilometres from the coast). The survey technique and recommended effort is described in Section 3.1
  
• 
  daytime searches for signs of activity, such as nests (dreys) in trees, scratches on tree trunks or scats on the ground below trees with hollows or dreys (description of the survey technique and recommended effort is described in Sections 3.3.9, 3.2.6 and 3.2.2)
  
• 
  stagwatching surveys at potential nest sites (dreys and tree hollows) The survey technique and recommended effort is described in Section 3.3.4
  
• 
  spotlight surveys conducted according to the method outlined in Section 3.3.3 along transects, tracks or roads (Note: depending on the nature of the site, additional surveys from a vehicle may also be made)
  
• 
  discussion with locals, particularly in areas where densities are low or the species’ presence is unconfirmed.
  

An arboreal cage trapping program where surveying in habitats other than jarrah forest (for example peppermint and tuart forest types) in conjunction with scat and spotlight surveys to determine the most effective survey technique for different habitats. However, the technique is time-consuming and spotlighting is equally effective.

A possible alternative survey method would be the use of hair sampling devices.

The deployment of camera traps may be an effective and time-efficient technique, particularly in localities where densities are low or the species’ presence requires confirmation.

Similar species in range

The western ringtail possum can be easily distinguished from the sympatric common brushtail possum as it is shorter, has smaller rounded ears and a slender prehensile tail which is as long as the rest of its body (Menkhorst & Knight 2004).

References

de Tores, P. J., Hayward, M.W. and Rosier, S. M. 2004. The western ringtail possum, Pseudocheirus occidentalis, and the quokka, Setonix brachyurus, case studies: Western Shield review, February 2003. Conservation Science Western Australia 5(2), 235–258.

de Tores, P. J. 2008. Western Ringtail Possum Pseudocheirus occidentalis. In ‘Mammals of Australia’ (Eds. Van Dyck, S. and R. Strahan) pp. 253-255 (Reed New Holland: Sydney).
DEWHA 2008a. 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.
DEWHA 2008b. Background paper to 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.
Jones, B., How, R.A and Kitchener, D.J. 1994a. A field study of Pseudocheirus occidentalis (Marsupialia: Petauridae). I Distribution and Habitat. Wildlife Research 21: 175-187.
Jones, B., How, R.A and Kitchener, D.J. 1994b. A field study of Pseudocheirus occidentalis (Marsupialia: Petauridae). II Population studies. Wildlife Research 21: 189-201.
Jones, B. 1995. Western Ringtail Possum, Pseudocheirus occidentalis (In) Mammals of Australia (Ed. R. Strahan) pp. 252-254 (Reed Books: Sydney).
Menkhorst, P. and Knight, F. 2004. A Field Guide to the Mammals of Australia. Second Edition. (Oxford University Press: Melbourne, Australia).
Wayne, A. F., Cowling, A., Ward, C.G., Rooney, J.F., Vellios, C.V., Lindenmayer, D.B. and Donnelly, C.F., 2005a. A comparison of survey methods for arboreal possums in jarrah forest, Western Australia. Wildlife Research 32: 701-714.
Wayne, A.F., Cowling, A., Lindenmayer, D.B., Ward, C.G., Vellios, C.V., Donnelly, C.F. and Calver, M. C. 2005b The abundance of a threatened arboreal marsupial in relation to anthropogenic disturbances at local and landscape scales in Mediterranean-type forests in south-western Australia. Biological Conservation 127: 463 – 476.