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

Abstract

Body size is often assumed to determine how successfully an individual can lead others with larger individuals being better leaders than smaller ones. But even if larger individuals are more readily followed, body size often correlates with specific behavioral patterns and it is thus unclear whether larger individuals are more often followed than smaller ones because of their size or because they behave in a certain way. To control for behavioral differences among differentially-sized leaders, we used biomimetic robotic fish (Robofish) of different sizes. Live guppies (Poecilia reticulata) are known to interact with Robofish in a similar way as with live conspecifics. Consequently, Robofish may serve as a conspecific-like leader that provides standardized behaviors irrespective of its size. We asked whether larger Robofish leaders are preferentially followed and whether the preferences of followers depend on own body size or risk-taking behavior ("boldness"). We found that live female guppies followed larger Robofish leaders in closer proximity than smaller ones and this pattern was independent of the followers' own body size as well as risk-taking behavior. Our study shows a "bigger is better" pattern in leadership that is independent of behavioral differences among differentially-sized leaders, followers' own size and risk-taking behavior.

Going Beyond the “Synthetic Method”: New Paradigms Cross-Fertilizing Robotics and Cognitive Neuroscience

“…Robotics applied to ethological studies, obviously, offers capabilities extending far beyond the previously mentioned methods, allowing one to create biomimetic artificial agents performing complex behaviors that require sophisticated locomotion patterns or coordinated moving (Butail et al, 2014;Phamduy et al, 2014;Abdai et al, 2018;Bierbach et al, 2020;Romano and Stefanini, 2021a), and producing several kind of signals (Partan et al, 2009;Polverino et al, 2019;Romano and Stefanini, 2021b). Biomimetic agents can be fully controlled, allowing one to test all subjects with an identical set of cues.…”

The Potential for Physiological Performance Curves to Shape Environmental Effects on Social Behavior

“…In self-organized moving groups, leadership has been shown to propagate from the front of the group ( Bumann and Krause, 1993 ; Nagy et al, 2010 ). Front positions are thought to be occupied by individuals who have more information about the surrounding environment or a greater need for resources and motivation to locate preferable environments ( Ioannou et al, 2015 ), therefore leadership can depend on resource requirements linked to body size and sex ( Fischhoff et al, 2007 ; Bierbach et al, 2020 ). The group members that successfully lead others and achieve their preferred outcome may be those with the highest physiological performance, for example those with the greatest aerobic capacity ( Killen et al, 2012a ) who can sustain more energetically-demanding positions or be better able to escape from attacks by predators, both costs of leadership associated with being at the front of moving groups ( Ioannou et al, 2019 ).…”

Biomimetic robots promote the 3Rs Principle in animal testing

“…In a recent publication, we used differentially-sized robotic leaders and found a bigger-is-better pattern as guppies regardless of own size followed larger robofish replicas more readily (Bierbach et al 2020). Focal individuals were only tested once and the robot leaders did not require training.…”