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Physics studies show that flocks of sheep change their leaders and achieve collective intelligence

Physics studies show that flocks of sheep change their leaders and achieve collective intelligence

Credit: Luis Gómez-Nava, Richard Bon and Fernando Peruani.

The collective movement of animals in a group is a fascinating topic of research for many scientists. Understanding these collective behaviors can sometimes inspire the development of strategies to promote positive social change, as well as technologies that mimic nature.


Many studies describe swarm behavior as a self-organized process, with individuals in the group constantly adjusting their direction and speed to eventually achieve “collective” movement. This perspective, however, does not take into account hierarchical structure exhibited by many groups of animals and possibly benefit from a “leader” leading the way.

Luis Gómez-Nava, Richard Bon and Fernando Peruani, three researchers at the Université Côte d’Azur, Université de Toulouse, and CY Cergy Paris Université, recently used the theory of physics to examine the collective behavior of small flocks of sheep. Their findings, published in Nature Physicsshow that by alternating the roles of leader and follower, the flock eventually achieves some form of “collective intelligence.”

“In most social animal systems, collective movement is not a continuous process, but occurs in episodes: phases of collective movement are interrupted, for example, to rest or feed,” Peruani told Phys.org. “However, most studies of collective movement, including experimental and theoretical, consider groups which remain, from beginning to end, in motion. Furthermore, it is often assumed that flock behavior requires individuals to continuously negotiate the direction of travel.”

A key goal of the recent work by Peruani and colleagues was to investigate the collective movement of an animal system in a way that explicitly takes into account the temporal aspect of the observed self-organizing process, specifically that the phases of collective movement have a beginning and an end. . In addition, the team wanted to adopt an alternative and holistic perspective, which considers the movement of an animal group as a set of “collective phases”.

“From this perspective, questions about the mechanisms of information exchange and consensus decision-making take on a new dimension,” Peruani explained.

In their experiment, Peruani and his colleagues closely studied the spontaneous behavior of small groups of sheep at different time intervals. They analyzed the trajectories of individual flock members and calculated the overall spatial order and orientation of the animals, while also assessing correlations between the speed at which individual animals moved.

“We first showed that none of the existing flocking models, or their extensions, are consistent with our observations,” Peruani said. “We then analyzed how information travels through the group, identifying an interaction network that is consistent with the data, and explored what information is transmitted through this network.”

A study shows that flocks of sheep change their leaders and achieve collective intelligence

Credit: Luis Gómez-Nava, Richard Bon and Fernando Peruani.

Interestingly, Peruani and his colleagues found that the network of interactions representing the behavior of the flocks they observed was highly hierarchical. In addition, they showed that the only information that propagates through this network is that related to the position of the sheep in the group.

Using their findings, the researchers built a model of animal collective movement that focuses on two key cognitive processes. These processes are the selection of a leader to lead the flock for a certain period of time and the mechanism underlying flock navigation.

“It is important that each phase of the collective movement has a temporal leader,” Peruani explained, “We investigated the mathematical properties of the resulting model to identify the advantages of the revealed collective strategy. I believe the main contribution is this: the animals, by using a hierarchical network of interactions to move together for a time, give complete control of the group to the temporal leader, but there is also a rapid turnover of temporal leaders.”

Essentially, the researchers’ findings suggest that while moving in flocks, sheep alternate between the roles of leader and follower. Leaders thus lead the group only for a certain period of time, before control of the group is transferred to another sheep.

“If the temporal leader has knowledge relevant to the group (eg the exit of the maze or the location of the food source), then the temporal leader will be able to effectively lead the group,” Peruani said “In this way, all members of the group use that knowledge. It is worth noting that this it only works if all individuals follow the temporal leader without question.”

The findings gathered by Peruani and his colleagues shed new light on the dynamics that underpin the collective movement of small flocks of sheep. However, to investigate the generalizability of these findings, further experiments with larger herds and different animals will need to be conducted.

“We asked: if there is a temporal leader at all times, how does the group share and process the information that each individual group member may have? Can the group perform information gathering to improve its ability to accurately navigate to a distant location? In short, does the group show collective intelligence?” Peruani said. “We have proven that by regularly changing the time leader, groups are able to demonstrate information gathering and collective intelligence.”

Overall, recent work by this team of researchers highlights the possibility that some natural strategies for collective animals take advantage of both hierarchical and democratic organizational schemes. In the future, their observations could spur new research investigating the physics and biology that underpin these intriguing collective animal behaviors.

“We are now investigating collective motion using groups of different agents,” Peruani added. “Specifically, we are comparing the spontaneous behavior of groups of lambs, young ewes and adult ewes to investigate whether sheep learn to follow weather leaders and behave as one with time. We also investigate how groups behave in complex environments such as mazes or arenas with different portions of food that can cause conflicts of interest within group members. And more generally, we investigate how collectives distribute and process information, using several tools of statistical mechanics.”

More information:
Luis Gómez-Nava et al., Intermittent collective locomotion in sheep results from leader-follower role alternation, Nature Physics (2022). DOI: 10.1038/s41567-022-01769-8

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Citation: Physics study shows flocks of sheep alternate their leader and achieve collective intelligence (2022, November 17) Retrieved November 18, 2022 from https://phys.org/news/2022-11-physics-sheep-flocks-alternate- leader.html

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