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Chaos as a strategy

A study analyzes the search strategy for food used by a marine snail. It is based on chaotic turns and movements. This search pattern, could be useful for search applications (drons, people rescue…) when there is no clear sign of the item that has to be found.

Hydrobia Ulvae. By H. Zell - Own work, CC BY-SA 3.0, Wikimedia.When the marine mollusk Hydrobia ulvae searches for food and has little information from the environment, it makes turns and movements with no regular pattern. They are complex movements more near to a chaotic dynamics than anything else. These chaotic turnings generate a movement pattern known as ‘Lévy walks’, which has been seen in other animals, from bacteria to marine birds, worms and snails.

The Lévy walk is a good search strategy. It draws a fractal structure, which optimizes search success in conditions where the items to be found may be either close or far away, and its location is unknown.

Frederic Bartumeus, ICREA researcher at the Centro de Estudios Avanzados de Blanes del CSIC (CEAB-CSIC) and the CREAF, explains that “it has been hypothesized that this complexity could be an answer to the environment complexity from the sensory and cognitive ‘point of view’ of the animal”. What we don’t know, he adds, “is whether Lévy walk is an answer to sensorial and cognitive reactions to the environment or is, actually, an inherent and genetically programmed behavior”. 

Bartumeus is co-author of a new study published in Nature Scientific Reports, that analyzes search patterns of marine snail Hydrobia ulvae. Tests with the animals have been done in the laboratory in order to control the environment where the animals are moving. Scientists have found out that when food is near enough and there are signs of it, the snails go towards it. But when food is far and animal receives no cue from it, the chaotic movement pattern appears and so the “Lévy walks’.

It would be, as they think, a search strategy, useful in critical moments, genetically transmitted in a natural selection process

This is the first research that analyzes temporal series of the turning behavior of  this marine snail. Scientists think this turning behavior is triggered by signals from “motor neurons, located near the foot of the animal or closer to the brain. It would be, therefore, as they think, a search strategy, useful in critical moments, which has been genetically transmitted through generations, in a natural selection process.

This would mean that it is the most successful searching strategy when there are no cues from the environment. Scientists believe that this search pattern, based on chaos, could be useful for search applications (drons, people rescue, sampling environmental sampling systems…) when there is no clear sign of the item that has to be found.

Reference article:

Signatures of chaos in animal search patterns. Andy M Reynolds, Frederic Bartumeus, Andrea Kölzsch & Johan van de Koppel. Scientific Reports 6, Article number: 23492 (2016) doi:10.1038/srep23492