The life history of Pseudocheirus occidentalis (Pseudocheiridae) in the jarrah forest of south-western Australia

Abstract

Life-history attributes are described for the threatened ngwayir or western ringtail possum (Pseudocheirus occidentalis) in inland jarrah (Eucalyptus marginata) forest east of Manjimup, south-western Australia. Data on 81 individuals were collected over 18 months. There was no sexual dimorphism and body size was similar to that found in other P. occidentalis populations, but larger than the closely related P. peregrinus in eastern Australia. Breeding at Chariup was more strongly seasonal than that of coastal populations, with 77% of births in May-June and the remainder in October-November. All neonates were singletons except for one instance of non-viable twins. No females bred twice in the same year. The growth rate of the head length of pouch young (<5 months of age) was 0.245-0.362 mm day-1 and curvilinear toward an asymptote thereafter. Temporal variations in body condition, coat condition and ectoparasites were significant. Mortality was highly seasonal (84% of deaths were April-September) and predominantly caused by predation, mainly by fox (Vulpes vulpes) and cat (Felis catus). More effective and strategic control of introduced predators prior to and during autumn/winter, could therefore improve the viability of jarrah forest populations. Nutrition appears to influence many of the life-history traits of P. occidentalis. Nutrition also may partly explain the differences in size, life history and conservation status between P. occidentalis and P. peregrinus.