Formidable females redux: male social integration into female networks and the value of dynamic multilayer networks

Abstract

The development of multi-layer network techniques is a boon for researchers who wish to understand how different interaction layers might influence each other, and how these in turn might influence group dynamics. Here, we investigate how integration between male and female grooming and aggression interaction networks influences male power trajectories in vervet monkeys Chlorocebus pygerythrus. Our previous analyses of this phenomenon (Young et al. 2017) used a mono-layer approach, and our aim here is to extend these analyses using a dynamic multilayer approach. To do so, we constructed a temporal series of male and female interaction layers. We then used a multivariate multilevel autoregression model to compare cross-lagged associations between a male’s centrality in the female grooming layer and changes in male Elo-ratings. Our results confirmed our original findings: changes in male centrality within the female grooming network were weakly but positively tied to changes in their Elo-ratings. However, the multi-layer network approach offered additional insights into this social process, identifying how changes in a male’s centrality cascade through the other network layers. This dynamic view indicates that the changes in Elo-ratings are likely to be short lived, but that male centrality within the female network had a much stronger impact throughout the multilayer network as a whole, especially on reducing inter-male aggression (i.e., aggression directed by males toward other males). We suggest that multilayer social network approaches can take advantage of increased amounts of social data that are more commonly collected these days, using a variety of methods. Such data are inherently multilevel and multilayered, and thus offer the ability to quantify more precisely the dynamics of animal social behaviours.

The consistency of individual centrality across time and networks in wild vervet monkeys

“…Individuals may have different centralities across different networks (e.g., grooming, aggression, play), which has also seldom been studied. Wild vervet monkeys have been found to keep consistent individual centralities across grooming and proximity networks (Blaszczyk, 2018; Bonnell et al, 2020; Borgeaud et al, 2017; Canteloup et al, 2020b). Assessing the extent of consistency in centrality across different behavioral networks is important because consistencies may indicate similar behavioral functions and yield insight into social personality traits, whereas inconsistencies would suggest different functions, ultimately helping to disentangle the establishment versus maintenance of the social structure.…”

“…This focus is problematic as the inclusion of juveniles in a network can affect the network centrality of adults (Fedurek & Lehmann, 2017). Moreover, studies used different data collection methods (scan sampling: Bonnell et al, 2020; Borgeaud et al, 2016, 2017; focal animal sampling: Blaszczyk, 2018) raising issues of comparability. We thus aimed to corroborate previous results on grooming networks through the use of a different data collection method than scan sampling that was previously used at our field site (Borgeaud et al, 2016, 2017).…”

Multilayer network analysis: new opportunities and challenges for studying animal social systems

“…Multilayer network analysis offers a promising means to capture these complexities and to investigate how changes in 1 layer may drive dynamics in others. Bonnell et al. (2021) present a new method for investigating these sorts of dependencies within multilayer networks and illustrate its use by applying it to better understand power dynamics within vervet monkey Chlorocebus pygerythrus groups.…”

Oil Palm Cultivation Critically Affects Sociality in an Endangered Malaysian Primate

“…We further investigated relative changes in individual scores of eigenvector centrality (EC) between habitats, uncovering in how far an individual's position in its social group may differ between forest and plantation. EC accounts for both direct and indirect network ties, re ecting an individual's importance in the social network while considering the importance of its neighbours 29,39,40 . It was found to be strongly linked to indicators of individual health and tness in group-living animals, including macaques 23,40,41 .…”

“…We created social networks in R version 3.4.4 (R Core Team 2020) using an undirected data structure with the function graph_from_data_frame from the package 'igraph' (version 1.2.5 82 ). For each individual, we extracted the binary degree and eigenvector centrality (EC), two commonly used network parameters to quantify individual social connectedness 39,29 .…”