Western Ringtail Possum  |  

The species has undergone a significant decline in population size and geographic range since European settlement; and is currently undergoing a severe decline due to predation; habitat loss and climate change.
The rate will depend on whether rainfall continues to decline and temperatures continue to increase based on recent history and climate change predictions; both are likely.
Regarded as one location due to climate change being the major threat that affects all populations; but occurs in five subpopulations that could be regarded as locations based on the combination of different threatening processes.
WRPs are among the species most likely to be impacted by predicted climate change in the south west because they have very specific habitat and dietary requirements; have a poor ability to migrate and have lost large areas of habitat.
Over the past 30 years there has been an up to 20 decline in rainfall in the south west of WA; with more reductions in rainfall and increased temperatures predicted due to global climate change (Timbal 2004; CSIRO 2009).
The South West Western Australia Sustainable Yields Project (CSIRO 2009) determined that in SW WA climate change has resulted in water runoff decreasing by approx. half due to a 10 15 decrease in annual rainfall since 1975.
If the species occurs in a variety of formerly several types of forest and woodlands now mostly closed habitats; is there a preferred habitat peppermint forest Does the species use refugia yes; dreys and hollows; used during the daytime Threatened species nomination form (include what is it and when is it used) Is the habitat restricted in extent or number of locations Yes No If Yes; provide details Coastal mature peppermint forest very restricted and most is now unsuitable because most is not closed canopy tree decline observed; due probably to the drying climate Is this species reliant on a threatened or priority species or ecological community Yes No If Yes; provide details Are there any other species (sympatric species) that may affect the conservation status of Yes No the nominated species If Yes; provide details brushtail possums outcompete ringtails for hollows.
In the case of taxa obligately dependent on other taxa for all or part of their life cycles; biologically appropriate values for the host taxon should be used. (IUCN 2001) Subpopulations are defined as geographically or otherwise distinct groups in the population between which there is little demographic or genetic exchange (typically one successful migrant individual or gamete per year or less). 5.1 Subpopulations Location Land tenure Survey information AOO Site habitat Condition Date of survey and No. (include coordinates) mature individuals Threatened species nomination form Southern Swan Coastal mostly See attachments See attachments Plain private Cape to Cape mixed public See attachments See attachments and private Upper Warren mostly See attachments See attachments nature reserve Other Forest Rivers mixed state See attachments See attachments forest and private land Near Albany mixed; See attachments See attachments mostly private 5.2 Population size (Australian context) (include how numbers were determined calculated) What is the total population size c. 3400 mature individuals What is the number of subpopulations What percentage of the population is 100 within WA What percentage of the population is 100 within Australia 5.3 Population dynamics (Australian context) (include how numbers were determined calculated) What is the number of mature c. individuals What is the number of immature unknown; varies with season individuals What is the number of senescing past N A reproductive individuals What is the maximum number of c. mature individuals per subpopulation What is the percentage of mature numbers above are for mature individuals individuals in the largest subpopulation What percentage of mature individuals 100 is within WA What percentage of global mature 100 individuals is within Australia What is the age of sexual maturity 1 year What is the life expectancy 3 6 years; but towards lower end nowadays Threatened species nomination form What is the generation length 3 years; now possibly 2 years What is the reproductive capacity (i.e. litter size or number of seeds) What is the reproductive success depends on nutritional status of food; see attachments 5.4 Population trend What is the current population trend Decreasing Increasing Stable (mature individuals) What is the percentage of the 80 over the past 10 years; see attachments population change and over what time period How has this been calculated observed for Upper Warren; inferred for other subpopulations If the trend is decreasing are the causes of the reduction understood Yes No Have the causes of the reduction ceased Yes No Are the causes of the reduction reversible Yes No Some are; some are not climate change not considered reversible in the medium term Is the reduction continuing (continuing decline) Yes No Has the change been observed; all of these estimated; inferred or is it suspected (direct observation; index of abundance appropriate to the species) When was the reduction or is it anticipated to occur Past Present Future What is the period of time for the past 10 and next 10 years for this evaluation reduction (in years and generations) Has there been a reduction in the number of subpopulations Yes No If Yes; provide details not in the past 10 years; although significant reduction in size of all subpopulations Are there extreme fluctuations in population size Yes No If Yes; provide details 5.5 Translocations and captive enclosed subpopulations Have there been translocations (introduction or re introduction) Yes No Are there proposed translocations (introduction or re introduction) Yes No Recovery Plan proposes translocations Are There Captive Enclosed Cultivated Subpopulations Yes No Karakamia and Upper Warren Threatened species nomination form Are there proposed captive enclosed cultivated subpopulations Yes No Are there self sustaining translocated subpopulations Yes No If Yes; provide details Almost all past translocations failed one near Yunderup has persisted so far in small numbers.
The issue of the threat of climate change; drought; and water availability was discussed and the potential to influence future decline.
Climate change; a drying climate; is a potential; projected threat.
The rate will depend on whether rainfall continues to decline and temperatures continue to increase based on recent history and climate change predictions; both are likely.
Criterion D There are 250 mature individuals the WRP does not qualify as CR or EN under this criterion. 2015 REVISED EVALUATION Conservation status Pseudocheirus occidentalis (Ngwayir or Western Ringtail Possum) is evaluated as Critically Endangered A2bce A3bce A4bce Justification The Ngwayir has an Area of Occupancy of 500 km2; small severely fragmented subpopulations and is continuing to decline; being threatened particularly by a drying climate (which affects the nutritional quality of its food) and hence survival and recruitment); Red Fox Vulpes vulpes and feral Cat Felis catus predation; urban development; inappropriate fire regimes and; possibly in the future; myrtle rust.
WRPs are among the species most likely to be impacted by predicted climate change in the south west because they have very specific habitat and dietary requirements; have a poor ability to migrate and have lost large areas of habitat.
Over the past 30 years there has been an approximate 20 per cent decline in rainfall in the south west of WA; with more reductions in rainfall and increased temperatures predicted due to global climate change (Timbal 2004).
Attachment While Southwestern Australia s rainfall was disappearing 2001 15; it was taking the possum Pseudocheirus occidentalis with it Barbara Jones; February 2016; landline SUMMARY For Southwestern Australia s ringtail possum; Pseudocheirus occidentalis; a 2015 re examination of regional population estimates; along with ringtail and rainfall decline outcomes; indicated that in 2000 2002; the two largest populations used the driest parts of the species 1990s footprint and probably accounted for about 95 of the species numbers in 2000 2002; the species largest occurrence (Upper Warren) probably accounted for about 80 of the species numbers; and about 80 of the area of the species 1990s footprint and then between 2002 and 2010 the only large coastal population (Southern Swan) started showing patchy declines that became increasingly common and were strongly linked to patchy impacts on stand growth (re foliation and de foliation) of dry and very dry years; and the retreating water table; and this population went on to lose about 60 65 of its 2003 numbers by 2015 between 2004 and 2009 the species largest reserved population (Perup; in the Upper Warren) was crashing; with probable retention of less than 1 of the 2000 2002 numbers persisting 2012 15 in combination; the recent declines of the two driest and largest populations seem to have left about 10 of the 2003 species numbers surviving in 2015 An entrenched 15 year climate trend suggests more critically dry years can be expected; and it would be no surprise if numbers halved again in a few years.
Fire can have significant impacts in urbanised environments; where remnants are relatively isolated and the patchiness of burns may be less; resulting in greater impact on WRPs.
This broadscale; high frequency; aseasonal burning in remnant vegetation and reserves (including urbanized fragments) has a deleterious impact on the WRP both in altering the ecology of the vegetation and direct impacts on individual survival.
In addition they are sensitive to drought induced stress.
In addition they are sensitive to drought induced stress.