Abstract
Studies of self-organizing groups like schools of fish or flocks of birds have sought to uncover the behavioral rules individuals use (local-level interactions) to coordinate their motion (global-level patterns). However, empirical studies tend to focus on short-term or one-off observations where coordination has already been established or describe transitions between different coordinated states. As a result, we have a poor understanding of how behavioral rules develop and are maintained in groups. Here, we study the emergence and repeatability of coordinated motion in shoals of stickleback fish (Gasterosteus aculeatus). Shoals were introduced to a simple environment, where their spatio-temporal position was deduced via video analysis. Using directional correlation between fish velocities and wavelet analysis of fish positions, we demonstrate how shoals that are initially uncoordinated in their motion quickly transition to a coordinated state with defined individual leader-follower roles. The identities of leaders and followers were repeatable across two trials, and coordination was reached more quickly during the second trial and by groups of fish with higher activity levels (tested before trials). The rapid emergence of coordinated motion and repeatability of social roles in stickleback fish shoals may act to reduce uncertainty of social interactions in the wild, where individuals live in a system with high fission-fusion dynamics and non-random patterns of association.
Highlights
Studies of self-organizing groups like schools of fish or flocks of birds have sought to uncover the behavioral rules individuals use to coordinate their motion (Couzin et al 2002; Herbert-Read 2016)
Experimental work and theoretical models have shown that individuals monitor and respond to nearby neighbors resulting in the emergence of coordinated motion in groups of insects (e.g., Kelley and Ouellette 2013; Attanasi et al 2014), fish (e.g., Herbert-Read et al 2011; Katz et al 2011), birds (e.g., Cavagna et al 2010; Bialek et al 2012; Pettit et al 2013; Ling et al 2019), and ungulates (e.g. King et al 2012; Torney et al 2018)
Leadership scores were variable within shoals (Figure 2a, b), and this variability was maximized when a correlation between two fishes' velocities (CV*) was greater than 0.5 (Figure 2c, d)
Summary
Studies of self-organizing groups like schools of fish or flocks of birds have sought to uncover the behavioral rules individuals use (local-level interactions) to coordinate their motion (global-level patterns) (Couzin et al 2002; Herbert-Read 2016). Experimental work and theoretical models have shown that individuals monitor and respond to nearby neighbors resulting in the emergence of coordinated motion in groups of insects (e.g., Kelley and Ouellette 2013; Attanasi et al 2014), fish (e.g., Herbert-Read et al 2011; Katz et al 2011), birds (e.g., Cavagna et al 2010; Bialek et al 2012; Pettit et al 2013; Ling et al 2019), and ungulates
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