Effect of Infant Presence on Social Networks of Sterilized and Intact Wild Female Balinese Macaques (Macaca fascicularis).

Gwennan Giraud,Fany Brotcorne,Pascal Poncin,Marie-Claude Huynen,Alain Hambuckers,Stefan Deleuze,Sebastian Sosa,I Wandia

doi:10.3390/ani11092538

Gwennan Giraud, Fany Brotcorne + Show 6 more

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https://doi.org/10.3390/ani11092538

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Abstract

Simple SummaryIn primates, social interactions are significantly influenced by the female reproductive cycle and the presence of infants. In particular, unweaned infants act as amplifiers of social interactions: they facilitate contact between group members while also triggering occasional conflicts. Sterilized females no longer having young offspring could see their social integration modified. We studied intact and recently sterilized wild female long-tailed macaques (Macaca fascicularis) to see if infant presence was influencing the females’ place and role in the social group. We used the social network analysis tool to compare grooming and proximity to other females for females in three nursing conditions (with young infant (YI), with old infant (OI), and non-nursing (NN). YI females were less involved in grooming but stayed in closer proximity to other females than OI and NN females. We suggest that YI females keeping proximity to others was a way to maximize their infants’ protection, while avoiding too direct social interactions, such as grooming, to protect them from kidnapping risk. Overall, sterilization did not deteriorate female social integration, at least shortly after the surgery. Further research should track the social status of non-nursing females over a long time period, in aid of making sound population management decisions.Contraception is increasingly used to control wild animal populations. However, as reproductive condition influences social interactions in primates, the absence of new offspring could influence the females’ social integration. We studied two groups of wild macaques (Macaca fascicularis) including females recently sterilized in the Ubud Monkey Forest, Indonesia. We used social network analysis to examine female grooming and proximity networks and investigated the role of infant presence on social centrality and group connectivity, while controlling for the fertility status (sterilized N = 14, intact N = 34). We compared the ego networks of females experiencing different nursing conditions (young infant (YI) vs. old infant (OI) vs. non-nursing (NN) females). YI females were less central in the grooming network than other females while being more central in proximity networks, suggesting they could keep proximity within the group to protect their infant from hazards, while decreasing direct grooming interactions, involving potential risks such as kidnapping. The centrality of sterilized and intact females was similar, except for the proximity network where sterilized females had more partners and a better group connectivity. These results confirm the influence of nursing condition in female macaque social networks and did not show any negative short-term effects of sterilization on social integration.

Highlights

In social mammals, reproductive status and the mere presence of infants may influence social associations and interactions, those conditions being largely under hormonal processes [1,2,3]
In accordance with our predictions, we found that young infant (YI) females were more frequently in contact (Figure 1a) and within 5 m of other females (Figure 1b) than old infant (OI) and nursing females (NN) females, but had a lower number of contact partners compared to OI females (Figure 1c) (Table 1)
Contrary to the proximity network, we found no significant difference in grooming duration given and received between NN, YI and OI females

Summary

Introduction

Reproductive status and the mere presence of infants may influence social associations and interactions, those conditions being largely under hormonal processes [1,2,3]. In cercopithecine primates, unweaned infants are mediators and amplifiers of female social ties since they play a role in the biological market [11,12]. Studies have shown that attraction to infants and its influence on social bonds are species-specific. Within the macaque genus, females of different species are highly to moderately permissive with their infants and more or less tolerant toward females approaching them, during the first month of the infant’s life [13,14]. Infant handling by group members is frequent and attraction for newborns is significant for matrilineal primates such as macaques and baboons where mothers are often the focus of other females’ attention [6,7,15,16]

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