Reintroduction biology of the eastern quoll (Dasyurus viverrinus)

Abstract

Translocations are a critical tool used to reverse biodiversity loss, and their outcomes hinge on a population's passage through the establishment (post-release effects drive population dynamics), growth (high rates of expansion), and finally, regulation (density dependence limits survival and recruitment) phases. However, management decisions are always made in the face of uncertainty, which have historically led to low levels of translocation success. In this thesis, I explored tactics, behaviour, movement, and recovery related to the reintroduction (translocation to a species' indigenous range) of the eastern quoll (Dasyurus viverrinus, 'murunguny' in the Indigenous Ngunnawal language) to a fenced, outdoor laboratory; Mulligans Flat Woodland Sanctuary, Australian Capital Territory (ACT). The eastern quoll is an endangered carnivorous marsupial of high conservation priority, with the potential to fulfil the mesopredator ecological role. I aimed harness the best available knowledge to improve reintroduction outcomes, and develop frameworks that could be applied to other translocation programmes. We conducted the reintroduction as a series of iterative trials from 2016 to 2019. I assessed eastern quolls using pre-release behavioural assays (Chapter 3), monitored their post-release survival and dispersal using VHF (Chapters 2-4) and GPS collars (Chapter 4), and monitored their population dynamics using the capture-mark-recapture method (Chapter 5). In Chapter 1, I summarised the literature relating to translocations, conservation fencing, and the eastern quoll. I also presented an overview of the species' reintroduction to Mulligans Flat to provide context for the project and the relationships between its Chapters. In Chapter 2, I demonstrated how iterative trials and adaptive management can improve reintroduction outcomes. By comparing survival and dispersal of eastern quolls across three trial reintroductions to Mulligans Flat, I showed how we can use learnings from trials to adapt tactics to encourage positive outcomes in later trials. In Chapter 3, I investigated whether behavioural measures in reintroduced eastern quolls could predict post-release survival and dispersal using the 'behavioural reaction norm' approach. I found individuals had consistent variation in behaviours (personality) as well as the capability to adjust behaviour over time (plasticity). These played a pivotal role in determining post-release performance, and therefore behavioural offer significant value as a conservation tool. In Chapter 4, I investigated how movement, habitat use and preference, and conspecific associations differed between residents (established individuals) and reinforcers (individuals translocated to reinforce a population). I revealed movements of eastern quolls at a greater spatio-temporal resolution than has ever been achieved for this species, and I revealed appropriate habitat for future reintroduction sites. In Chapter 5, I demonstrated how demographic parameters can reveal threats to persistence, inform thresholds for management, and create targets for removing species from the IUCN Red List. I visualised an ambitious end point ('stretch goal', i.e., recovery of the eastern quoll species within 10 years), and projected the population size and habitat required to achieve this goal (back-casting). In Chapter 6, I took the learnings from this thesis and developed the 'Translocation Continuum' framework. The framework creates clarity around translocation 'phases', their criteria, strategies, tactics, evaluation measures, and expected outcomes. I discuss the confines of 'success' and 'failure' labels in translocation science, and the importance of parsimonious decision making that maximises learning with the least amount of loss. In the final Chapter 7, I provide a summary of the key findings from each of my Chapters, and synthesise how these substantially contributed to translocation and conservation science.