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 fe