Patterns of infant handling and relatedness in Barbary macaques (Macaca sylvanus) on Gibraltar

Abstract

Among papionin primates, the Barbary macaque (Macaca sylvanus) shows the most extensive interactions between infants and group members other than the mother. Two different types of interactions occur: (1) long-lasting dyadic interactions between a handler and an infant, and (2) brief triadic interactions between two handlers involving an infant. Previous investigations showed that infant handling by males is best explained as use of infants to manage relationships with other males. In contrast, no adaptive explanation for infant handling by females emerged. Here, we compared the infant-handling pattern between subadult/adult males and subadult/adult females in a free-ranging group of 46 Barbary macaques on Gibraltar to test whether the relationship management hypothesis also applies to female handlers. We further investigated the infant-handling pattern of juveniles and used microsatellite markers to estimate relatedness between infant handlers and the infant's mother. We found that males, females and juveniles all participated extensively in triadic interactions using infants of above-average related females. In contrast, only males and juveniles were highly involved in dyadic interactions with infants of related females, while females rarely handled infants other than their own. The pattern of infant handling was entirely compatible with the predictions of the relationship management hypothesis for males and mostly so for females. Moreover, our genetic analysis revealed that males and females differ in their partner choice: while females preferred to interact with related females, males had no significant preference to interact with related males. We further discuss the observed above-average relatedness values between infant handlers and the infant's mother in the light of kin-selection theory.

Triadic awareness predicts partner choice in male–infant–male interactions in Barbary macaques

“…The agonistic buffering hypothesis (Deag and Crook 1971) proposes that holding an infant, males can approach even higher ranking males without being attacked and have a chance to improve and/or re-establish disturbed relationships and reduce stress. The relationship management hypothesis emphasizes, that bridging gives males the opportunity to interact peacefully in general and not only after a conflict and that the interactions may contribute to male-male bonding, that is profitable in various ways (Kümmerli and Martin 2008) even long term, e.g. via coalition formation (Widdig et al 2000;Young et al 2014a).…”

Cooperation in wild Barbary macaques: factors affecting free partner choice

“…In Barbary macaques, adults often interact with infants and juveniles and use them as social buffer to facilitate approach and affiliation (e.g. Deag and Crook 1971;Paul et al 1996;Kümmerli and Martin 2008). Kin relationships may also interact with dominance status during partner choice.…”

The male and female perspective in the link between male infant care and mating behaviour in Barbary macaques

“…An alternative, non‐mutually exclusive driver of male care, particularly in Barbary macaques, is improved access to infants for frequent triadic man–infant–man interactions. These interactions help males to establish and maintain social bonds with other males (Kalbitz et al, ; Kuběnová et al, ; Kümmerli & Martin, ; Paul et al, ) which may reduce aggression among males (Deag & Crook, ) and help them to retain support in coalition (Paul et al, ). The benefit of social bonding may outweigh the cost of infant care.…”