Spider monkeys share tips about where to find food by changing their social groups in a “clever system for sharing insider knowledge”, research has shown.
They were observed to frequently switch subgroups of three or more individuals in a way that enabled them to share information about the location of fruit trees and timing of when they would ripen.
It meant they could not only complement each other’s knowledge, but also “combine their information in such a way as to produce new knowledge”, the research found.
The report, published in the journal njp Complexity, said: “An example would be if one subset of individuals would contribute the location of a food source and another subset the timing of the fruiting of that source.
“The resulting, combined knowledge by both subsets of individuals would be synergistic in the sense of allowing all of them to exploit the food source according to its location and timing”.
It concluded the evidence was a “compelling example of collective intelligence in natural conditions”.
The study, involving scientists from Heriot-Watt University, the University of Edinburgh and the National Autonomous University of Mexico, was based on seven years of field observations in Mexico’s Yucatán peninsula.
Scientists used the data to explore a feature of Geoffroy’s spider monkey social behaviour in which group members split into small subgroups, then rejoin in different combinations to enhance shared knowledge.
The same subgroup might never forage together twice.
Dr Matthew Silk, an ecologist from the University of Edinburgh, said: “It isn’t random social mingling. It’s a clever system for sharing insider knowledge about where the best fruit trees are located across their forest home.
“By constantly changing their subgroups, monkeys who know different parts of the forest can share information about where fruit is available.
“We tracked individual monkeys’ movements and mapped out their core ranges, or the areas each monkey knows well. Some parts of the forest are known by multiple monkeys, like a town’s most popular restaurant, while others are known by only one or two monkeys, like a hidden gem.
“There’s enough overlap for monkeys to meet and exchange tips, but enough separation that each monkey scouts different parts of the forest. This maximises the whole group’s collective coverage of the best feeding spots.”
Ross Walker, a PhD student at Heriot-Watt, developed a method of mathematical modelling to analyse what the monkeys gain from these relationships.
“We’ve shown that there’s an optimal middle ground between the monkeys sticking together and spreading out too far,” he said.
“It’s best when individuals explore different areas, but still reconnect often enough to pool what they’ve learned.”
The team used data on a group of Geoffroy’s spider monkeys collected by experienced observers between January 2012 and December 2017.
The species, which is considered endangered, is also known as the Central American spider monkey and the black-handed spider monkey.
Prof Gabriel Ramos-Fernandez from the National Autonomous University of Mexico said: “We have shown that the fluid social dynamics of spider monkeys has an important consequence for their foraging success.
“By exploring their environment in a distributed fashion and then coming together to share their uniquely obtained information, the group as a whole can know the forest better than a single individual could on its own.”
