title: Inherent noise appears as a Lévy walk in fish schools.
abstract: Recent experimental and observational data have revealed that the internal structures of collective animal groups are not fixed in time. Rather, individuals can produce noise continuously within their group. These individuals' movements on the inside of the group, which appear to collapse the global order and information transfer, can enable interactions with various neighbors. In this study, we show that noise generated inherently in a school of ayus (Plecoglossus altivelis) is characterized by various power-law behaviors. First, we show that individual fish move faster than Brownian walkers with respect to the center of the mass of the school as a super-diffusive behavior, as seen in starling flocks. Second, we assess neighbor shuffling by measuring the duration of pair-wise contact and find that this distribution obeys the power law. Finally, we show that an individual's movement in the center of a mass reference frame displays a Lévy walk pattern. Our findings suggest that inherent noise (i.e., movements and changes in the relations between neighbors in a directed group) is dynamically self-organized in both time and space. In particular, Lévy walk in schools can be regarded as a well-balanced movement to facilitate dynamic collective motion and information transfer throughout the group.
authors.affiliation: School of Fundamental Science and Engineering, Waseda University, Shinjuku, Tokyo, 1698050, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Murakami
authors.affiliation: Faculty of Engineering, Information and Systems, Tsukuba University, Tsukuba, Ibaraki, 3050006, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Niizato
authors.affiliation: Research Institute for Science and Engineering, Waseda University, Shinjuku, Tokyo, 1698050, Japan.
authors.forename: Takenori
authors.initials: T
authors.lastname: Tomaru
authors.affiliation: Science &Technology Entrepreneurship Laboratory (e-square), Osaka University, Suita, Osaka, 5650871, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Nishiyama
authors.affiliation: School of Fundamental Science and Engineering, Waseda University, Shinjuku, Tokyo, 1698050, Japan.
authors.forename: Yukio-Pegio
authors.initials: YP
authors.lastname: Gunji
mesh_terms: D000465:Algorithms; D000818:Animals; D001522:Behavior, Animal; D005399:Fishes; D008962:Models, Theoretical; D009622:Noise