Sex, Rank and Age Differences in the Japanese Macaque (Macaca fuscata yakui) Participation in Inter‐Group Encounters

Abstract

In many species interactions among group are often characterized by agonistic behaviour. Although animals may participate in inter-group encounters in different ways, depending on their energetic requirements, reproductive tactics, and/or developmental stage, the proximate causes affecting an animal's participation in inter-group encounters are still poorly understood. Indeed, many studies have analysed the behaviour of males and females during inter-group encounters without considering the importance of additional factors (e.g. rank). This study focuses on wild non-provisioned Japanese macaques (Macaca fuscata yakui) living on Yakushima Island, Japan. It aims to determine how monkeys of different sex, age, and rank behave during inter-group encounters and it discusses the implications and consequences of their behaviour on group composition and male dispersal. Males participated significantly more than females in inter-group encounters, by displaying more aggressive or affiliative behaviour. High-ranking and/or adult males were more aggressive than lowranking and/or subadult males during encounters occurring in the mating season and they also showed more herding behaviour. This trend was not found in inter-group encounters occurring during the non-mating season. Finally, males which then emigrated to new groups were low-ranking and/or subadult individuals. Those males displayed more affiliative behaviour towards foreign males than males which did emigrate. These data indicate that in non-territorial species with male dominance over female and high competition for mating partners males play an active, and often aggressive, role during inter-group encounter while female participation is scarce. Factors such as age, rank and period of the year (in seasonally breeding species) have to be taken into considerations when analysing interactions between groups and their effects on group composition and social behaviour.

Individual participation in intergroup contests is mediated by numerical assessment strategies in black howler and tufted capuchin monkeys

“…For example, sexual dimorphism and the presence of dependent offspring can lead to higher costs of participation for females relative to males [2]. Similarly, better body condition and priority of access to contested resources may lower the costs of participation for high-ranking individuals while increasing benefits from contesting access to key resources [18,40,[47][48][49]. If group members adjust their participation accordingly, the maximum collective benefit may still be obtained [42], but sex-and rankbased differences in individual assessment may emerge that affect willingness to participate (e.g.…”

Group augmentation, collective action, and territorial boundary patrols by male chimpanzees

“…Although theoretical work has provided support for Olson's perspective (3), findings from studies of participation in between-group aggression, a frequent type of collective action in primates and other group-living animals, have been particularly difficult to interpret (4,5). As predicted, in many species that form dominance hierarchies, high-ranking individuals participate in intergroup encounters more often than do low-ranking individuals (6)(7)(8)(9)(10)(11)(12)(13). Nevertheless, their reasons for doing so are unresolved.…”

Experimental test of female black howler monkey (Alouatta Pigra) responses to loud calls from potentially infanticidal males: Effects of numeric odds, vulnerable offspring, and companion behavior

“…Such costs and benefits could include the probability of a physical assault being directed at her, the probability of her group winning the encounter, and the probability that a contest loss would have fitness consequences (e.g., based on her reproductive investment and the risk of infanticide). Although a handful of studies quantitatively analyzed the role of female primates during intergroup conflicts (e.g., Cheney, 1981;Hill, 1994;Perry, 1996;Steenbeek, 1999;Steenbeek et al, 1999;Reichard and Sommer, 1997;Fashing, 2001;Lazaro-Pareo, 2001;Nunn and Deaner, 2004;Sicotte and Macintosh, 2004;Majolo et al, 2005), few used experimental protocols to manipulate the costs and benefits of female participation (Thomas langurs: Wich et al, 2002aWich et al, ,b, 2004. Here, experimental playback techniques were used to explore the participation of female Belizean black howler monkeys (Alouatta pigra) in loud call displays directed at extragroup males.…”