School of BioSciences - Theses
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ItemBirds in the sky, fish in the sea, money in the bank: quantitative methods for more effective conservation( 2021)My approach in this thesis was to explore how to wring more information out of existing data to reduce uncertainty, improve decision-making and hope to generate better conservation outcomes. I explore and develop a range of quantitative tools to this end. I look at three key areas: dealing with uncertainty, structuring decision making, and improving the use of existing information. I consider these concepts over three thematic case studies: monitoring the abundance of three vulture species in Cambodia, trading-off the costs and benefits of releasing information publicly when a new species or population is discovered, and comparing use of optimisation and project prioritisation protocols to allocate funding to species conservation efforts. In the first case-study, I develop new Bayesian hierarchical model to estimate vulture abundance, and compare the inferences available from this approach with less specialised approaches previously used. In the second case-study I develop a decision-making framework to allow decision-makers to explicitly trade-off costs and benefits, and apply the method to data collected from informants who have made these types of decisions themselves. In the final section, I explore whether additional information can improve optimisation to allocate funding, and compare performance in terms of expected avoided extinctions of the optimisation approach with a project prioritisation protocol. I find that there is indeed much more we can learn from the information we have. But this is not a free lunch – work needs to be done to uncover opportunities, and technical skills are often needed to make best use of them, and assumptions must often be made to draw conclusions.
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ItemRobust prediction and decision strategies for managing extinction risks under climate change( 2016)Effective management of biodiversity requires decision strategies that are robust to the uncertainty embodied in predictions of habitat suitability and environmental change. This is particularly relevant in the context of climate change, which may interact with existing threats in unexpected ways. Predictive modelling has become important for addressing questions about climate change impacts. In particular, correlative species distribution models (SDMs) are popular for predicting species' fates, and have been noted as effective tools for guiding conservation decisions. However, SDM predictions are uncertain due to our imperfect understanding of the processes underlying species-environment associations, and, crucially, imprecision in predictions of regional climate change. While this is widely recognised, SDM prediction uncertainty is frequently overlooked, and practical approaches to handling this uncertainty are rare. When SDMs are used to investigate questions of species' persistence during times of environmental change, failure to consider uncertainty about the arrangement and quality of habitat may lead to flawed inferences and ineffective management. It is therefore essential that we improve our understanding of key uncertainties, and develop methods that explicitly handle uncertainty in a way that promotes sensible management decisions. In this thesis, I explore these issues through case studies of the mountain pygmy-possum, Burramys parvus, in the alpine region of south-eastern Australia. I draw on a range of quantitative tools and classical decision theory to: (1) determine the magnitude of uncertainty about habitat suitability due to SDM predictor choice, and how this varies under climate change; (2) develop a framework for identifying the optimal spatial allocation of resources for species' conservation under climate change, given uncertain predictions of habitat suitability; (3) explore the utility of abundance time series for improving our understanding of environmental dynamics influencing populations; (4) combine SDMs and models of population dynamics with decision theory to assess the extent to which predictions are refined by explicitly including population processes; and (5) develop a suite of open source software tools that facilitate common ecological modelling tasks, making rigorous investigation of climate change questions more computationally efficient and feasible. I found that standard approaches to model evaluation obscure key differences amongst competing SDMs, suggesting that consideration of ecological relevance during model construction is essential. I showed that despite extensive uncertainty about future habitat, conservation actions can be prioritised in a way that reflects managers' appetites for risk and reward. I demonstrated that for spatially-structured populations, hierarchical models can reveal the spatial scales at which environmental processes control population growth. Regional synchrony in population dynamics is evident for B. parvus, but local, density-independent environmental forces are more important in determining abundance trajectories. Finally, I demonstrated that habitat change is an unreliable surrogate for a species' response to climate change. Predictions about the distribution and quality of future habitat for B. parvus are uncertain. However, this is an inevitable challenge when forecasting species' fates. Importantly, it does not preclude effective management. The way forward is to recognise and account for uncertainty in ecological models, thereby enabling sensible conservation decisions for species impacted by climate change.
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ItemCoping style and group dynamics in a cooperative breeder, the superb fairy-wren (Malurus cyaneus)( 2016)Group dynamics – the movements and interactions of individuals within and between groups – are known to play an important role in influencing key life history events such as dispersal and reproduction. Nevertheless, there is considerable variation in conspecific interactions and life history strategies that remains poorly understood. Over recent years, a growing number of studies have shown that individual animals consistently differ in their behaviour over time and across contexts. This phenomenon is typically referred to as ‘animal personality’ or ‘temperament’ and evidence is accumulating that these behavioural differences can help to explain the form and expression of life-history traits. However, currently most evidence for a relationship between personality and life-history traits comes from theoretical or captive studies. There is a need to verify these ideas under natural circumstances, to assess the true impact of personality on individual life-histories and fitness. In this thesis I investigated whether and how individual coping style (a narrow-sense proxy of personality) is related to the performance of different tasks during breeding and to individual natal dispersal strategies in a wild population of cooperatively breeding superb fairy-wrens (Malurus cyaneus). In this species, males can disperse at any point in their life and help their parents raise successive broods while still at home, while most females disperse in their first year. By conducting behavioural assays, of fairy-wren behaviours (boldness, exploration, aggression) under controlled conditions, I first established that individual fairy-wrens in my population indeed show distinct coping styles. I then tested whether individual differences in coping style where related to contributions to key tasks within social groups, specifically alloparental care (nestling feeding behaviour), territory defence (responses to simulated conspecific territorial intrusions) and nest defence (responses to a novel object at active nests). To test for relationships between coping style and dispersal outcomes, I experimentally created temporary breeding vacancies by removing male breeders from territories without helpers to prompt dispersal by a male helper from one of the neighbouring territories into the vacant breeding position. Finally, I used data on natural cases of male and female dispersal, collected over six consecutive years of population monitoring to test whether individual dispersal strategies were related to coping style. My findings suggest that coping style has much less influence on group dynamics than suggested by theoretical and captive studies. First, cooperative division of tasks such as offspring provisioning and nest defence did not occur during breeding, nor did individuals consistently differ in the amount of help provided. Coping style did not affect feeding rate or response to a simulated conspecific intruder, and only played a role during inspection of a novel object near the nest when more than one bird was present: birds with relatively fast coping styles (exploratory, active and bold in the artificial environment) responded more strongly to the object than group members with slower coping styles. In general, the social context had the strongest effect on behaviour. Individuals responded much more strongly to the novel object and the simulated conspecific intruder when in the company of other group members than when alone. Second, coping style only played a role in dispersal among young males. Males that dispersed during their first year of life on average had a faster coping style than those that delayed dispersal. Among males that dispersed after their first year, dispersal timing was not related to coping style, but rather to the likelihood of inheriting the natal territory. In females, dispersal timing was not related to coping style, but rather to hatch timing. In superb fairy-wrens the social and physical environment seem to play a larger role than personality in how individuals behave within their group and in the dispersal decisions they make. Task division did not occur and individuals instead seemed to be flexible and responsive to environmental stimuli in relation to offspring care and defence. Investment in cooperation is therefore not a good predictor of life-history strategies in this species. With regard to dispersal strategies, males with faster coping styles indeed disperse or die young, as predicted by the pace-of-life syndrome hypothesis. Due to the reduced variance in coping styles among males that disperse later, variation in dispersal timing among these males is rather due to external factors such as stochasticity of dispersal opportunities and dispersal motivation based on conditions in the natal territory. For females dispersal is a prerequisite for reproduction, which leads to higher dispersal motivation compared to males. The importance of hatch date for dispersal timing indicates that environmental conditions outweigh coping style as a predictor of dispersal strategies. Together, these results show that theoretical and captive studies may overestimate the role of personality in life-history strategies in the wild by oversimplifying the environment. Captive studies may teach us about underlying mechanisms, but only by testing predictions in the field will we truly know their significance in individual life- histories and their consequences for evolution.