Maggs, GB; (2017) The ecology and conservation of wild and reintroduced populations of the critically endangered Mauritius olive white-eye Zosterops chloronothos. Doctoral thesis , UCL (University College London).

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Abstract

The world is facing a biodiversity crisis and nowhere is that more apparent than on oceanic islands with recent research identifying islands as conservation priority areas and so increasing the importance of conservation for island endemics. Despite this some of the most remarkable success stores in the history of conservation have come from island nations with countries like Mauritius among the few to buck the biodiversity loss trend. However, species conservation often requires intensive management to reduce limiting factors and save endangered species from extinction. But with limited resources and knowledge accurately assessing the impact of management techniques is essential to reduce uncertainty and enable effective decision-making. Here I have developed decision-making tools to identify the role of management for a critically endangered passerine, the Mauritius olive white-eye (Zosterops chloronothos), within both a wild and reintroduced population. Specifically I combined field datasets with statistical, economic and social analytical approaches through mixed-effects models, population modelling, knowledge exchange, expert elicitation, population viability analysis and cost-effectiveness analysis to guide efficient long-term management; identifying the role of invasive species management and supplementary feeding. I quantitatively identified invasive rats as a major limiting factor to the wild olive white-eye population, however, rat management can mitigate this threat increasing annual productivity 5-6 fold and preventing further population decline. These findings identify rat management as a viable option and provide evidence to pursue large-scale, long-term management in the form of a ‘mainland island’. By comparing four rat management techniques I created decision-making tools to identify the area required for a mainland island and the most cost-effective technique against extinction risk; comparing trapping, ground based poisoning, self-resetting traps and predator-proof fencing. Within the reintroduced population the supplementary feeding (SF) programme is exponentially increasing with olive white-eye population growth. By identifying the mismatch between supply and demand I show that the demand for SF peaks during energetically expensive phases of the breeding cycle, when natural plant resource availability is low, and in the morning. This identifies short-term refinements responding to peaks in demand and a potential long-term exit strategy through the increase of natural plant resource availability, reducing demand over time. The approaches taken in this study illustrate how the combination of conservation tools can increase our understanding of both the ecology and conservation of highly threatened species focusing on both wild and reintroduced populations of the Mauritius olive white-eye. Here I identify the role of management and create decision-making tools to enable the timely application of robust and viable long-term management while accounting for financial, logistical and epistemic uncertainty. These findings have a broad relevance for other highly threatened species programmes experiencing similar limiting factors, resource limitations and long-term uncertainty by minimising the risk of decision-making and enabling evidence-based management. This is especially relevant for island endemics where invasive species are one of the biggest threats, intensive management through reintroduction and supplementary feeding is required and actions have to be taken quickly to avert species extinction.

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