Noise drives schools of fish
doi:10.1038/nindia.2020.40 Published online 4 March 2020
From flocks of starlings to marching locusts, behavior of animal groups has long puzzled scientists. Apart from a pioneering study of direction switching in locust nymphs, researchers have disregarded the contribution of noise in group behavior.
Now, an international research team has shed new light on how noise plays a role in shaping the dynamics of schools of fish1. They have shown the important role of noise in the collective behaviour of animal groups in cichlid fish.
The team, including researchers from the Indian Institute of Science and National Centre for Biological Sciences, TIFR, both in Bangalore, India performed experiments in freshwater juvenile cichlid fish in a laboratory tank shallow enough to restrict motion to two dimensions.
They studied small and medium sized groups, each consisting 15, 30 and 60 fish. They found that the fewer the fish in a group, the greater the intrinsic noise and therefore the likelihood of alignment. This implies extremely simple rules of individual behaviour — fish either change their direction spontaneously, or copy the direction of a randomly chosen fish.
They say that noise arising from random interactions between individuals might serve as a mechanism for driving particular group behaviours.
From a biological perspective, it is well known that collective behaviour offers many advantages to organisms, with implications for their survival and fitness, the researchers say. The noise-induced schooling, they say, may provide key insights into how it shaped origin and evolution of group behaviour in animals.
1. Jhawar, J. et al. Noise-induced schooling of fish. Nat. Phys. (2020)Doi:10.1038/s41567-020-0787-y