Initiative, Personality and Leadership in Pairs of Foraging Fish

Abstract

Studies of coordinated movement have found that, in many animal species, bolder individuals are more likely to initiate movement and shyer individuals to follow. Here, we show that in pairs of foraging stickleback fish, leadership is not merely a passive consequence of temperamental differences. Instead, the act of initiating a joint foraging trip out of cover itself brings about a change in the role that an individual plays throughout the subsequent trip, and success in recruiting a partner affects an individual's tendency to initiate the next trip. On each joint trip, whichever fish took the initiative in leading out of cover gains greater influence over its partner's behaviour, which persists even after several changes in position (i.e. termination attempts and re-joining). During any given trip, the initiator is less responsive to its partner's movements than during trips initiated by the partner. An individual's personality had an important effect on its response to failure to recruit a partner: while bold fish were unaffected by failures to initiate a joint trip, shy individuals were less likely to attempt another initiation after a failure. This difference provides a positive feedback mechanism that can partially stabilise social roles within the pair, but it is not strong enough to prevent occasional swaps, with individuals dynamically adjusting their responses to one another as they exchange roles.

Experience overrides personality differences in the tendency to follow but not in the tendency to lead

“…Water quality was maintained through an undergravel filtration system. Fish were allowed to acclimate for two days in the compartments, and then individual temperament was assessed using the same set-up adopted in our previous experiments [11,15,21,25,28,29]. An experimental tank (70 Â 30 Â 30 cm) was divided lengthwise into two long lanes with an opaque plastic partition (figure 1).…”

“…Furthermore, personality differences and responsiveness can coevolve through a positive feedback [22]. In support of these ideas, many empirical studies have shown that shyer individuals are more responsive to others, whereas bolder individuals are less responsive [15,[23][24][25]. Consequently, one might predict that bolder individuals should perform poorly when forced to adopt the role of follower, whereas shy individuals should adapt more easily to the role of leader.…”

Context-dependent hierarchies in pigeons

“…However, the relationship between social structure and leadership is still unknown in some of the most rapid, large-scale, and impressive examples of collective motion: bird flocks and fish shoals. Initial simulations of these groups posed anonymous, homogeneous interaction rules (12, 13), but individual differences are now the focus of both theoretical and empirical investigations (3,(14)(15)(16)(17)(18)(19). Elucidating how social structure and individual differences affect group decision-making across a range of taxonomic groups will put the study of collective behavior into a broader biological context.…”

Analysis of Pairwise Interactions in a Maximum Likelihood Sense to Identify Leaders in a Group

“…Further, it is believed that these individuals accomplish these tasks by relying on environmental information available to them rather than social feedback (Dyer et al, 2009;King et al, 2009). Past studies in collective animal behavior have explained the emergence of leadership through several mechanisms, including the availability of extra group knowledge Ioannou et al, 2011), hunger (Krause et al, 1992;Krause, 1993), personality traits (Leblond and Reebs, 2006;Nakayama et al, 2012), and morphophysiological variations (Reebs, 2001).…”

“…Our approach of identifying leaders via the strength of interactions over experimental time assumes that the leaders are consistent throughout the entire observation, in time and in space, which may not be always the case (Nakayama et al, 2012). When these conditions lose validity, one may seek to partition the observation into contiguous measurements and implement the approach separately, on each measurement.…”