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.
Highlights
Non-human primates show a high degree of behavioral diversity in terms of ecology, sociality, and cognition, across species (Mitani et al, 2012), and within the same species (Struhsaker, 2000; Strier, 2003, 2016)
Intra-specific variation can happen at various levels, including differences (i) across conspecific groups and populations and (ii) across individuals of the same group
Inter-individual variation in primate behavior has been the focus of abundant research; it has shown how individuals within the same group may use different behavioral strategies depending on their age, dominance rank, sex, or personality (e.g., Hosey, 2005; Lehmann and Boesch, 2008, 2009; Slater et al, 2009; Lonsdorf et al, 2014; Kulik et al, 2015a,b)
Summary
Non-human primates (hereafter, primates) show a high degree of behavioral diversity in terms of ecology, sociality, and cognition, across species (Mitani et al, 2012), and within the same species (Struhsaker, 2000; Strier, 2003, 2016). Larger groups may offer a larger availability of potential social partners, so that individuals may more find a suitable conspecific to interact with (see Majolo et al, 2008, across primates, and Majolo et al, 2009, on Japanese macaques). Larger groups might face higher within-group food competition, leading to a significant decrease in tolerance over food sources (across primates: Janson and van Schaik, 1988; Isbell, 1991). Group size may predict behavioral differences across conspecific groups in terms of social interactions, dominance style, social tolerance, and neophobia
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