Alternate modes of leadership in collective behaviour

Understanding interactions between individuals is imperative for predicting how groups may react to changing environmental landscapes. Animal populations have displayed variation in behaviour when responding to different environmental cues. Variation in behaviour has been linked to differences in physiology, including metabolic phenotypes and locomotor performance. Understanding how these differences in individuals present themselves in groups provides insight into how physiology affects group behaviour, and how this may change in different contexts. Collective movement in animals is an increasingly prevalent theme in behavioural research, and understanding how and why groups decide to move is critical to our knowledge of animal life. Group movement may emerge from the decisions of one or few individuals, i.e. leadership, or be a shared decision by all individuals. Leadership has been previously linked to individual behavioural traits, which has also been related to physiological differences, however the specific links between physiology and leadership are understudied. Using laboratory experiments, I investigated the role of physiology in leadership of schools of fish, and how different contexts altered leadership in groups in order to examine how groups move and the mechanisms underpinning leadership. In the first data chapter, I tested whether metabolic composition of groups affected leadership by compiling groups of nine fish according to their standard metabolic rate and recorded their swimming behaviour. We measured behaviour at 15 °C, and again at 18 °C to see how temperature increases affect leadership and group dynamics. We found that metabolic composition had no consistent effect on group behaviour and leadership, but increases in temperature caused fish to be less synchronised and leadership to be disrupted. The metabolic cost of digestion has been shown to affect individual behaviour. Our second experiment investigated how group behaviour changed with feeding and time since feeding. Before and during feeding showed relationships between behaviour and meal size, where fish that ate the most were found to be followers when a leader was accelerating, however a fish who has eaten more food is more likely to be a leader when turning. There was no association between meal size and leadership after feeding, however leadership in groups changed before and after feeding events. Our results from chapter 3 and 4 indicated that different environmental contexts disrupted group behaviour, rather than creating consistent differences in specific individual leadership ability. To see how social context affected these metrics, I tested individual swimming performance testing how cost of transport related to leadership and see how individuals alter their voluntary swim speeds to stay within groups and how this relates to their physiological optimum. We found that higher cumulative costs are found when swimming alone compared to groups. Leadership is also not linked to deviation from optimum swim speed, showing that leaders in groups do not influence groups to swim at their optimum swim speed. This study confirms that leadership is not more costly in terms of transport speed, and overall swimming in groups is less costly than swimming alone. These results provide evidence that changing contexts affect group behaviour and leadership in schools of fish. Leadership may not be attributed to one or few specific individuals however how leadership is distributed among individuals may still change in different contexts. Chapters 3 and 4 suggest that physiological processes affect leadership behaviour, and chapter 5 shows that social context will affect group behaviour. Our results provide insight into how leadership in groups change in different contexts and how I may expect collective behaviour to change with environmental variation groups may experience in the wild

Perceptions of Marine Science as a Field-based Discipline: Highlighting Digital Twinning of the Oceans as a Complementary and More Inclusive Pathway into a Career in the Marine Sciences

No abstract available

Guidelines for reporting methods to estimate metabolic rates by aquatic intermittent-flow respirometry

Interest in the measurement of metabolic rates is growing rapidly, because of the importance of metabolism in advancing our understanding of organismal physiology, behaviour, evolution and responses to environmental change. The study of metabolism in aquatic animals is undergoing an especially pronounced expansion, with more researchers utilising intermittent-flow respirometry as a research tool than ever before. Aquatic respirometry measures the rate of oxygen uptake as a proxy for metabolic rate, and the intermittent-flow technique has numerous strengths for use with aquatic animals, allowing metabolic rate to be repeatedly estimated on individual animals over several hours or days and during exposure to various conditions or stimuli. There are, however, no published guidelines for the reporting of methodological details when using this method. Here, we provide the first guidelines for reporting intermittent-flow respirometry methods, in the form of a checklist of criteria that we consider to be the minimum required for the interpretation, evaluation and replication of experiments using intermittent-flow respirometry. Furthermore, using a survey of the existing literature, we show that there has been incomplete and inconsistent reporting of methods for intermittent-flow respirometry over the past few decades. Use of the provided checklist of required criteria by researchers when publishing their work should increase consistency of the reporting of methods for studies that use intermittent-flow respirometry. With the steep increase in studies using intermittent-flow respirometry, now is the ideal time to standardise reporting of methods, so that - in the future - data can be properly assessed by other scientists and conservationists

The potential for physiological performance curves to shape environmental effects on social behavior

As individual animals are exposed to varying environmental conditions, phenotypic plasticity will occur in a vast array of physiological traits. For example, shifts in factors such as temperature and oxygen availability can affect the energy demand, cardiovascular system, and neuromuscular function of animals that in turn impact individual behavior. Here, we argue that nonlinear changes in the physiological traits and performance of animals across environmental gradients—known as physiological performance curves—may have wide-ranging effects on the behavior of individual social group members and the functioning of animal social groups as a whole. Previous work has demonstrated how variation between individuals can have profound implications for socially living animals, as well as how environmental conditions affect social behavior. However, the importance of variation between individuals in how they respond to changing environmental conditions has so far been largely overlooked in the context of animal social behavior. First, we consider the broad effects that individual variation in performance curves may have on the behavior of socially living animals, including: (1) changes in the rank order of performance capacity among group mates across environments; (2) environment-dependent changes in the amount of among- and within-individual variation, and (3) differences among group members in terms of the environmental optima, the critical environmental limits, and the peak capacity and breadth of performance. We then consider the ecological implications of these effects for a range of socially mediated phenomena, including within-group conflict, within- and among group assortment, collective movement, social foraging, predator-prey interactions and disease and parasite transfer. We end by outlining the type of empirical work required to test the implications for physiological performance curves in social behavior

Guidelines for reporting methods to estimate metabolic rates by aquatic intermittent-flow respirometry

Interest in the measurement of metabolic rates is growing rapidly, because of the importance of metabolism in advancing our understanding of organismal physiology, behaviour, evolution and responses to environmental change. The study of metabolism in aquatic animals is undergoing an especially pronounced expansion, with more researchers utilising intermittent-flow respirometry as a research tool than ever before. Aquatic respirometry measures the rate of oxygen uptake as a proxy for metabolic rate, and the intermittent-flow technique has numerous strengths for use with aquatic animals, allowing metabolic rate to be repeatedly estimated on individual animals over several hours or days and during exposure to various conditions or stimuli. There are, however, no published guidelines for the reporting of methodological details when using this method. Here, we provide the first guidelines for reporting intermittent-flow respirometry methods, in the form of a checklist of criteria that we consider to be the minimum required for the interpretation, evaluation and replication of experiments using intermittent-flow respirometry. Furthermore, using a survey of the existing literature, we show that there has been incomplete and inconsistent reporting of methods for intermittent-flow respirometry over the past few decades. Use of the provided checklist of required criteria by researchers when publishing their work should increase consistency of the reporting of methods for studies that use intermittent-flow respirometry. With the steep increase in studies using intermittent-flow respirometry, now is the ideal time to standardise reporting of methods, so that – in the future – data can be properly assessed by other scientists and conservationists