How infant presence influences social behaviour between adults in barbary macaques

Popular Abstract

Macaque politics and influential infants
How infants influence social behaviour in adult Barbary macaques

To befriend or not to befriend? Under what circumstances do animals act friendly to each other, and when do they act aggressively? Amid the dynamic and turbulent social landscape of macaque societies, individuals need to constantly evaluate their ever-changing social landscape. Family ties, friendly alliances, and place in the social hierarchy are all taken into consideration before acting dominant or submissive, aggressive or friendly. Other factors such as an individual’s personality and history, or environmental factors such as food availability and predation can also have strong consequences. A miscalculation can have violent consequences and can irrevocably alter the social standing of the individuals involved. In Barbary macaque societies the smallest members may have one of the biggest impacts on the social dynamics of the group. Barbary macaques have a keen interest in infants and all members of the group, regardless of relation, interact with infants. There is even competition to act as babysitters. As a result, the birth of an infant can have a significant impact on the mother’s standing in the group. However over 40 years of research has yet to conclude what benefit this has or why this behaviour occurs.

This affinity for cute and cuddly infants has brought them to the forefront of Barbary macaque politics. Interactions between males can be tense affairs, but the presence of an infant seems to de-escalate the interaction. In a potentially volatile situation, males have been seen using infants as “agonistic buffers”, where two males will hold an infant between them to reduce the chance of aggression. In the closely related Tibetan macaque, the competition to interact with infants has resulted in a ‘groom for access’ bartering system, whereby adults groom the mother in exchange for access to her infant. These interactions strengthen the social bonds between the other group members and expand her social network. This study explored how the presence and proximity of infants can influence adult social temperament: are adult macaques friendlier and less aggressive when there are babies around?

Four measures were used to determine how infants influence social behaviour in adults; aggression, measured by rate of aggressive interactions, pro social behaviour, measured by time spent grooming others, anxiety, measured by scratching rate and time spent self-grooming, and social tolerance, measured by how long the adults would spend next to each other. In the presence of infants, social tolerance and pro social behaviour increased five and eight times respectively, with adults spending more time in each other’s company and grooming each other. The study also provided evidence that ‘groom for access’ behaviour may also be present in Barbary macaques. However, the presence of infants had no discernible impact on aggression or anxiety. I suggest that infants act as social facilitators within macaque society. Infants attract adults and thus bring them into contact with their mothers or carers, enabling social interactions and strengthening bonds between adults.

This study suggests that infants may influence the social dynamics of the group merely by their presence. However, in many captive Barbary macaque groups, breeding is restricted due to the capacity of the enclosure or risk of inbreeding. Looking deeper into the impacts on behaviour of removing infants from a group may uncover important welfare implications. In captive environments where groups are smaller and often more densely populated, aggression can pose a serious risk to the welfare of the animals. Frequent encounters with hostile group members with fewer opportunities for escape or avoidance can cause this aggression to escalate. This can result in serious injury, or an individual being ostracized from the group if the individual has lost its social ties to other members. Infants may hold the key to group cohesion by strengthening and expanding the social network among adults.

This study took place at Apenheul Primate Park, where twelve adult barbary macaques with their five new infants over a period of six months. It took a further three months to code and analyse the video recordings. All observations were non-invasive with no changes made to the Barbary’s caretaking routine and there was no contact between myself and the macaques. The method was designed to be simplistic and easily replicated with the hope that future studies will continue this research on other captive and wild groups. New research exploring the differences in behaviour between breeding and non-breeding captive groups may reveal how the absence of infants impacts group dynamics.

• author: Rayner, Kerne
• supervisor: Anders Brodin
• organization: Degree Projects in Biology
• course: BION03 20212
• year: 2022
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9103226
• date added to LUP: 2022-11-16 08:57:51
• date last changed: 2022-11-16 08:57:51