Guppies prefer to follow large (robot) leaders irrespective of own size

Abstract

13Body size is often assumed to determine how successful an individual can lead others with larger individuals 14 being more likely to lead than smaller ones. However, direct evidence for such a relation is scarce. Furthermore, 15 even if larger individuals are more likely to lead, body size correlates often with specific behavioral patterns 16 (e.g., swimming capacity) and it is thus unclear whether larger individuals are more often followed than smaller 17 ones because they are larger or because they behave in a certain way. To control for behavioral differences 18 among differentially-sized leaders, we used biomimetic robotic fish -Robofish -of different sizes. Robofish is 19 accepted as a conspecific by live guppies (Poecilia reticulata) and provides standardized behaviors irrespective 20 of its size. We specifically asked whether larger leaders are preferentially followed when behavior is controlled 21 for and whether the preferences of followers depend on their own body size or their risk taking behavior 22 ('boldness'). We found that live guppies followed larger Robofish leaders closer than smaller ones and this 23 pattern was independent of the followers' own body size as well as risk-taking behavior. This is the first study 24 that shows a 'bigger is better' pattern in leadership in shoaling fish that is fully independent of behavioral 25 differences between differentially-sized leaders and followers' own size and personality. 26

Guppies Prefer to Follow Large (Robot) Leaders Irrespective of Own Size

“…Furthermore, we like to thank Angelika Szengel and Hai Nguyen for their help in developing the Robofish and Christopher Schutz and Apollonia Landes for their help during experimentation. This manuscript has been released as a pre-print at bioRxiv (Bierbach et al, 2018c).…”