School of BioSciences - Theses
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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.