Abstract
The western ringtail possum (Pseudocheirus occidentalis) is listed nationally and internationally as a "Threatened Species': Populations are diminishing due to habitat loss, particularly from building development in coastal regions of south-west Western Australia. A translocation program is attempting to re-establish populations within the species' inferred geographic range at the time of European settlement. We monitored the fates of 67 translocated possums to determine ultimate causes of death. Mortality rates due to predation by both exotic and native carnivores were unsustainably high. Survivorship modelling identified some intrinsic and extrinsic proximate factors underlying the susceptibility of translocated individuals to predation, both in the short term and following establishment of territories. Numbers of common brushtail possums resident at the release site, together with pre-translocation white blood cell counts of individual western ringtail possums, affected survival of the latter species immediately post translocation. Rainfall and temperature affected survivorship in the longer term. We outline the mechanisms by which these factors are likely to operate and discuss the implications of our findings for the future management of the species.