Intra-specific Variation in the Social Behavior of Barbary macaques (Macaca sylvanus)

Abstract

Non-human primates show an impressive behavioral diversity, both across and within species. However, the factors explaining intra-specific behavioral variation across groups and individuals are yet understudied. Here, we aimed to assess how group size and living conditions (i.e., captive, semi-free-ranging, wild) are linked to behavioral variation in 5 groups of Barbary macaques (N=137 individuals). In each group, we collected observational data on the time individuals spent in social interactions and on the group dominance style, along with experimental data on social tolerance over food and neophobia. Our results showed that differences in group size predicted differences in the time spent in social interactions, with smaller groups spending a higher proportion of time in close spatial proximity, but a lower proportion of time grooming. Moreover, group size predicted variation in dominance style, with smaller groups being more despotic. Social tolerance was affected by both group size and living conditions, being higher in smaller groups and in groups living in less natural conditions. Finally, individual characteristics also explained variation in social tolerance and neophobia, with socially integrated individuals having higher access to food sources, and higher-ranking ones being more neophobic. Overall, our results support the view that intra-specific variation is a crucial aspect in primate social behavior and call for more comparative studies to better understand the sources of within-species variation.

Prosociality in a Despotic Society

“…Our results are in stark contrast with previous reports on prosocial preferences in captive Japanese macaques ($0%, 15 ). Consistent with the prediction that independently breeding free or semi free-ranging primates have lower social tolerance than captive populations, [71][72][73][74] our study group showed lower grouplevel social tolerance (Pielou's J 0 = 0.13) than the previously tested population residing in a more restricted captive setting (Pielou's J 0 = 0.32). 15 It must be noted that our group-level tolerance measure was limited to focal individuals and not the entire population.…”

Prosociality in a despotic society

“…Our results are in stark contrast with previous reports on prosociality in captive Japanese macaque (∼ 0%, (10)). Consistent with the prediction that independently breeding free or semi free-ranging primates have lower social tolerance than captive populations (59–62), our study group showed lower group-level social tolerance (0.13) than the previously tested population residing in a more restricted captive setting (0.32) (10). It must be noted that our group level tolerance measure was limited to focal individuals and not the entire population.…”

Prosociality in a despotic society

“…Our results are in stark contrast with previous reports on prosocial preferences in captive Japanese macaques (∼0%, 15 ). Consistent with the prediction that independently breeding free or semi free-ranging primates have lower social tolerance than captive populations, 71 , 72 , 73 , 74 our study group showed lower group-level social tolerance (Pielou’s J′ = 0.13) than the previously tested population residing in a more restricted captive setting (Pielou’s J′ = 0.32). 15 It must be noted that our group-level tolerance measure was limited to focal individuals and not the entire population.…”