抄録
In this study, we examine the radical difference between a single and a few individuals behavior. To investigate this difference, we use a fish (Plecoglossus altivelis, ayu or sweetfish) in an unfamiliar environment. We allow the fish to swim freely in a large shallow tank in a controlled laboratory and we track the fish's trajectories. In our experiment, although all trajectories of individuals show Lévy walk behavior, which is known as the optimal strategy for resolving the trade-off between exploration and exploitation, those trajectories of individuals were markedly different depending on whether they were alone or in a group. Our result suggests that the concepts of “whole” for a single fish and a group may be different. Furthermore, we also find that a leader of a group frequently changes though a trial.
