Spider monkeys have adjusted the group size to optimize for the search fruit

The scrambling Geoffroy, Central American representatives of the family of spider monkeys, form a subgroup whose size adapts to the number of fruit-bearing trees. However, they are guided not only by its own considerations, but also on the behavior of other dogs. This strategy allows to efficiently find food in changing conditions, noted in an article for the journal Frontiers in Robotics and AI.

The social life of many animals is subject to the dynamics of fission-fusion. This means that individuals in the group are periodically merged into sub-groups which exist for a relatively short time and do not have a rigid size or composition. It is assumed that this adaptation helps more efficient use of feed resources. However, zoologists still do not fully understand how animals decide to join a subgroup or leave it.

A team of specialists, led by Gabriel Ramos-Fernandez (Gabriel Ramos-Fernandez) from the National Autonomous University of Mexico decided to study this question on the example koat Geoffroy (Ateles geoffroyi) — Central American primates from the family of spider monkeys (Atelidae). They live in groups of 20-40 individuals, and feed mainly on fruit.

Researchers within two years watched the behavior of the group of 47 koat living in a protected area near the town of Punta Laguna in the Mexican part of the Yucatan Peninsula. Every day for five hours, the team members every 20 minutes, recorded the composition of the subgroups, which broke up a group of monkeys. Typically, each of them included two to 17 individuals and has existed for one to two hours. In addition, monitored the number of fruits on 15 species of trees that the scrambling visited the most.

The obtained data is analyzed with the help of mathematical apparatus, borrowed from game theory. It turned out that taking the decision to join the company or relatives to leave her, the scrambling guided by the choices of other individuals, and also map the size of the subgroup with the number of fruit-bearing trees. This allows to determine the optimal subgroup in which the benefits of more efficient search for food outweighs the need to share it with other people.

Choice koat does not always accurately match the environment. However, they used a strategy well suited to survival in environments where food availability is constantly changing, the authors note. According to them, the behavior of monkeys testifies to the effectiveness of a decentralized approach to decision-making: despite the fact that primates are fed by individual companies, the benefits of this are all members of the group.

The social life of many animals is highly complex. For example, belugas (Delphinapterus leucas) can generate seven different types of groups. As shown by a recent study, they are related and unrelated individuals.

Sergey Knee High

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