The influence of a demographic change on social relationships among male golden snub-nosed monkeys (Rhinopithecus roxellana)

Abstract

It has been suggested that social relationships are more likely to be prone to variation in the dispersing sex than the philopatric sex. However, we know less about the dynamics of all-male groups in male-dispersing species than we do about other types of primate groups. We studied male sociality in a captive group of golden snub-nosed monkeys (Rhinopithecus roxellana), which was composed of a one-male unit (OMU, N = 7) and an all-male unit (AMU, N = 7 or 8), in Shanghai Wild Animal Park, China. Using data collected for 6 months, during which there was a demographic change in the AMU and the alpha male was replaced by a newcomer, we found that a dramatic change in social ranks occurred accompanied by elevated aggression following this social upheaval. A proximity-based social network analysis revealed that members did not associate randomly any more but formed differentiated relationships post-upheaval, resulting in three distinct sub-units in the AMU. In terms of inter-unit interactions, significant changes were found in the affiliations between the male juvenile of OMU and AMU individuals. He interacted with AMU individuals randomly and frequently pre-upheaval, but cut down his affiliations and had a preferred partner post-upheaval, who was a member of the dominant male's sub-unit. Our findings suggest that social networks in the dispersing sex are dynamic structures and vary by some demographic change (e.g., individual immigration) in the studied species. We also put forward that individual dominance could be a criterion when the male juvenile chooses partners before he immigrates into a group. In conclusion, the high level of behavioral flexibility of the dispersing sex could be an evolutional strategy and good for individuals' future dispersing life.

Examining postmounting grooming in male golden snub‐nosed monkeys to investigate the functions of same‐sex mounts

“…In all‐male groups of golden snub‐nosed monkeys, dyadic proximity‐based association has been deemed a measure to distinguish the formation and composition of different cliques, in which individuals are frequently close to each other, form alliances and cooperatively defend food resources (Huang et al, 2018; Zhang et al, 2012; Huang, unpublished data). We did not detect significant correlation between proximity‐based association and the occurrence of same‐sex mounts among dyads.…”

“…There were no affiliative interactions but occasional aggression between adults or subadults from the two units, while juveniles of the OMU frequently joined the AMU and interacted with the bachelors. Particularly, the male juvenile of the OMU spent up to 30% of his time associating with the AMU individuals (Figure 3 in Huang et al, 2018). We thus tested the affiliation hypothesis on the AMU individuals ( n = 7−8) and the needing to learn hypothesis on the four AMU juveniles and the one male juvenile from the OMU ( n = 5).…”

“…As the April social upheaval led to changes in the social relationships among the AMU individuals, we used two matrices of dyadic proximity‐based association to calculate proximity indices pre‐ (January to March 2015) and postupheaval (April to June 2015) (Huang et al, 2018). Since there was no demographic change or distinct rank reversals before the social upheaval (Figure 1 in Huang et al, 2017), we thus considered the dyadic association levels from November 2014 to March 2015 to be equivalent to those from January to March 2015.…”

Dominance and social interaction patterns in brown capuchin monkey (Cebus [Sapajus] apella) social networks

“…To contextualize our findings, we characterize the demographics of our group and provide analyses of the dominance hierarchy. We use social network analyses to capture the complex combination of individual‐specific (e.g., age, sex, and rank), dyad‐specific (e.g., kinship, age difference, rank difference, sex concordance, and mutuality), and group‐specific (e.g., network centrality) factors that relate to social relationships in primates (Balasubramaniam et al, 2018; Beisner et al, 2015; Beisner et al, 2020; Borgeaud et al, 2017; Brent, 2015; de Waal & Embree, 1998; Finn et al, 2019; Huang et al, 2018; Kasper & Voelkl, 2009; McCowan et al, 2016). In previous studies, separate social networks developed based on individual behavioral categories (e.g., grooming, proximity, aggression, and play) reveal differences in demographic patterns and centrality across networks within a group (Brent et al, 2013; Canteloup et al, 2021; de Lima & Ferreira, 2021; Lehmann & Ross, 2011; Norscia & Palagi, 2015; Pereira et al, 2020; Smith‐Aguilar et al, 2019).…”