Social networks shape monkey “culture”

A new study, published in Current Biology, shows that squirrel monkeys who are at the heart of their social group pick up innovations first, and are more likely to acquire new cultural variations in behaviour like novel foraging techniques.

Dr Nicolas Claidière, Ms Emily Messer and Professor Andrew Whiten of the University of St Andrews in collaboration with Dr Will Hoppitt of Anglia Ruskin University studied both our East and West squirrel monkeys. They examined their social networks by recording who spent time with whom when the monkeys were in the vicinity of an “artificial fruit” that could be used to obtain food rewards by using two different techniques, lift or pivot (Figure 1).

Sophisticated statistical analysis of this information revealed the details of the monkeys’ social networks which helped the researchers visualize which monkeys were at the heart of the network and which were more peripheral (Figure 2). Each monkey was rated on a measure of their ‘centrality’ within the group.

Boa the alpha male in the East group was briefly separated and trained how to use the lift technique and his equivalent, Rio in the West group was trained to use the pivot technique, they were then reunited with their respective groups.

The scientists found that monkeys who were well-connected were the most likely to successfully pick up the new technique seeded in their group. They were also more likely to acquire the lift technique in the group seeded with ‘lift’, versus the pivot technique in the group seeded with ‘pivot’, so the alpha males were truly the hubs of these two different monkey ‘cultures’.

Professor Whiten, from the University of St Andrews, said: “Our study shows that innovations do not just spread randomly in primate groups, but as in humans, are shaped by the monkeys’ social networks”.

Dr Claidiere said: “Research interest in social learning and social network analysis has surged in recent years, and our results are likely to stimulate further research on the spread of innovations in animal social networks.

“We suspect that our focus on a social network relevant to the diffusion of foraging innovations can explain why we found an effect of the network centrality of individuals on their learning.

“Previous research has focused on other relationships, like who grooms whom, which may not correlate with the monkeys’ observational learning in the same way”.

Emily Messer, noted another aspect of the study. “We also found that maternal relationships explained parts of the social network, so some of the diffusion of the new foraging habits were also probably reflecting an emphasis on learning within families,” she said.

Click here to lead you to the abstract of the article in Current Biology

University of St Andrews researchers Dr Erica van de Waal and Professor Andrew Whiten and Christèle Borgeaud of the University of Neuchâtel have just published in the journal Science about the ability of vervet monkeys to conform to local feeding traditions.

In Living Links and Budongo Trail here in Edinburgh Zoo we do multiple studies on culture and how our primates can learn from each other, however doing this in the wild can be far more challenging, a challenge that Erica, Andy and Christèle overcame with a beautifully precise and effective experiment.

Like many species, vervet monkey infants learn a lot about life from watching their mothers, especially in instances of food choice. In this study four groups of vervet monkeys (total of 109 monkeys) in the Mawana private game reserve in South Africa were introduced to two different colours of corn.

Two groups were trained to eat pink corn and two groups were trained to eat the blue. This training phase was accomplished by making the ‘unpreferred’ food colour choice taste bitter by using aloe extracts from local plants. Approximately 4-6 months after the initial training, the corn was reintroduced to the groups with neither of the coloured corn being treated, thus making both palatable options.

Interesting the monkeys remembered which was their preferred colour choice and infants that had not seen coloured corn before only ate the same colour corn as their mothers did. In fact some of the infants sat the box of the unpreferred coloured corn to eat the ‘right’ colour, says Andy Whiten.

Not only do infant vervet monkeys adopt the ‘right’ colour corn from watching their mothers, males that emigrate to new groups will conform to eat the same colour corn as their new community. For example Groot was part of a group that was trained to eat the blue corn, as all male vervets that reach sexual maturity do he left his group to find another to be part of. When he arrived he saw that they were eating the pink corn, after a brief amount of time watching them he then joined in to eat the pink corn too.

By changing his preconceived ideas on what is appropriate to eat Groot could benefit from the new groups’ local knowledge. Professor Whiten said “It may make sense in nature, where the knowledge of the locals is often the best guide to what are the optimal behaviours in their environment”, thus the “when-in-Rome” mentality makes sense.

There was one exception in the study, a male named Lekker emigrated and immediately became the dominant male of new troop and he did not adopt their feeding preferences. This then created more questions. Did he not take on their traditions because he was dominant and felt no need to adopt the social conformity, or was he just stubbornly set in his ways? Will his new group then conform to what he eats? Since this only happened in one case, more research is required to gain further insight into social status and conformity in vervet monkeys.

Reference

van de Waal, E., Borgeaud, C., and Whiten, A. (2013). Potent Social Learning and Conformity Shape a Wild Primate’s Foraging Decisions. Science 340, 483-485.