(ORDO NEWS) — Physicists from three French universities have studied the movement of sheep in a herd. Scientists have shown that sheep coordinate movement with each other, and the behavior of the herd falls into phases. Moreover, at each phase, the sheep re-select their leader.
Sometimes it seems that sheep are smarter than people.
The collective movement of animals in a group is an important research topic for many scientists.
Understanding this collective behavior can sometimes inspire the development of strategies to promote positive social change, as well as technologies that mimic nature. This is especially important for modeling the swarm movement of robots.
Many studies describe gregarious behavior as a self-organizing process in which individuals in a group constantly adapt their direction and speed in order to eventually achieve a “collective” optimum of movement.
This view, however, fails to take into account the hierarchical structure common to many animal groups and the possible benefits of having a “leader” to show the way.
Luis Gomez-Nava, Richard Bon and Fernando Peruani from the University of Côte d’Azur, the University of Toulouse and the University of Paris Cergy investigated the collective behavior of small groups of sheep.
Their results show that individuals in the herd change their roles: they become either leaders or followers. In this way, the herd eventually achieves some form of “collective intelligence”.
How does the herd move?
“In most herd animals, collective movement is not a continuous process, it occurs in episodes: phases of collective movement are interrupted, for example, for rest or feeding,” said Peruani, lead author of the study.
“However, most studies of collective movement look at groups that are constantly on the move. It is often assumed that gregarious behavior requires individuals to constantly “negotiate” about the direction of movement.
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 members of the group, recorded the spatial order and orientation of the animals, and assessed correlations between the speeds at which individual animals moved.
To begin with, the scientists found that none of the existing models of herd movement works. So how do they move?
The scientists found that the nature of interactions in the herd, firstly, broke up into episodes, and secondly, was quite clearly hierarchical. That is, during one episode the herd always had one leader.
Peruani says the animals give full control of the group to a temporary leader, but such leaders often change.
In essence, the researchers’ work suggests that as they move through the herd, sheep alternate between being a leader and a follower. Thus, the leaders lead the group only for a certain period of time before control of the group passes to another sheep.
“If the interim leader has the knowledge the group needs (such as the way out of the maze or the location of the food source), then he will be able to effectively guide the group,” Peruani said.
“So all members of the group benefit from this knowledge. It should be noted that the leader becomes the leader only if all individuals decide to follow him.
Running in a circle
Quite unexpectedly, the model proposed by French physicists was confirmed in the movement of sheep on a Chinese farm. (We talked about it)
The sheep have been moving in circles for two weeks now. In the model proposed by scientists, such a failure is easily explained: when moving in a circle, there is no leader or all sheep are leaders (this is the same).
It is not clear when the movement phase should end and when the leader should be changed. If the sheep really behave as the French physicists described, the flock must walk in circles for a very long time, until all the sheep stop at once and scatter.
Another thing is that this behavior is a kind of “looping” or failure, so it is quite rare.
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