Spatial and temporal variation in declining eastern quoll (Dasyurus viverrinus) populations in Tasmania

The Australian fauna has endured numerous extinctions and declines in recent history. In particular, Australian mammals have experienced disproportionately more extinctions than their overseas counterparts, with many other species now only persisting on offshore islands after disappearing from their former mainland habitats. Once widespread throughout south-eastern Australia, the eastern quoll (Dasyurus viverrinus) is now considered extinct on the mainland, with the last confirmed sighting in Sydney in 1 963 . By contrast, eastern quoll populations in Tasmania were, until recently, presumed to be relatively stable and secure. However, spotlighting survey results suggest that the species may now be undergoing rapid and continuing decline. The aim of the current study was to further investigate this suspected decline, by measuring long-term changes in eastern quoll populations at a number of sites across Tasmania, and identifying factors that could have contributed to any observed population changes. Eastern quoll populations were surveyed using live capture and release at three study sites, with three replicate surveys performed at two-monthly intervals at each site. Results from the present study were compared with historical data from previous studies at these sites to gauge the extent of any local population changes. Significant reductions of >60% were observed in the number of quolls trapped at both Cradoc and Cradle Mountain, with no eastern quolls observed during any surveys at the Buckland study site. These declines appear to meet the criteria for listing the species as endangered under the Tasmanian Threatened Species Protection Act 1995 and the IUCN Red List of Threatened Species. A range of morphometric data and biological samples was collected from captured eastern quolls to assist in identifying potential causes of decline. Population structure, body condition, reproductive output and the health and disease status of captured quolls were compared across sites and between years. Several significant trends were observed in areas such as the development and timing of key reproductive stages, changes in population demographics and shifts in coat-colour ratios. From the findings of this study, critical information gaps were identified and several hypotheses were formulated to guide the management of key threats, halt further reductions, and ideally reverse the recent declines in eastern quolls