Emergent runaway into an avoidance area in a swarm of soldier crabs.
Emergent behavior that arises from a mass effect is one of the most striking aspects of collective animal groups. Investigating such behavior would be important in order to understand how individuals interact with their neighbors. Although there are many experiments that have used collective animals to investigate social learning or conflict between individuals and society such as that between a fish and a school, reports on mass effects are rare. In this study, we show that a swarm of soldier crabs could spontaneously enter a water pool, which are usually avoided, by forming densely populated part of a swarm at the edge of the water pool. Moreover, we show that the observed behavior can be explained by the model of collective behavior based on inherent noise that is individuals' different velocities in a directed group. Our results suggest that inherent noise, which is widely seen in collective animals, can contribute to formation and/or maintenance of a swarm and that the dense swarm can enter the pool by means of enhanced inherent noise.
Department of Earth & Planetary Sciences, Kobe University, Kobe, Hyogo, Japan.
Hisashi
H
Murakami
Department of Earth & Planetary Sciences, Kobe University, Kobe, Hyogo, Japan.
Takenori
T
Tomaru
Science & Technology Entrepreneurship Laboratory (e-square), Osaka University, Osaka, Japan.
Yuta
Y
Nishiyama
Faculty of Textile Science and Technology, Shinshu University, Ueda, Nagano, Japan.
Toru
T
Moriyama
Faculty of Engineering, Information and Systems, Tsukuba University, Tsukuba, Ibaraki, Japan.
Takayuki
T
Niizato
Department of Intermedia Art and Science, School of Fundamental Science and Engineering, Waseda University, Tokyo, Japan.
Yukio-Pegio
YP
Gunji
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D003386:Brachyura / Q000502:physiology*; D008399:Mass Behavior; D008954:Models, Biological; D009622:Noise; D045483:Rivers