Individuals living in groups have to achieve collective action for successful territorial defense. Because conflicts between neighboring groups always involve risks and costs, individuals must base their decision to participate in a given conflict on an evaluation of the trade-off between potential costs and benefits. Since group members may differ in motivation to engage in group encounters, they exhibit different levels of participation in conflicts. In this study, we investigated factors influencing participation in intergroup encounters in Verreaux’s sifakas (Propithecus verreauxi), a group-living primate from Madagascar. Over a period of 12 months, we studied eight adjacent sifaka groups in Kirindy Forest. We observed 71 encounters between known neighboring groups in which adult females and males participated equally as often. No individual participated in every encounter, and non-participation occurred more often in larger groups. Females participated less often in encounters when they had dependent infants, presumably to reduce the risk of infanticide. Male participation was influenced by social status: dominant males participated in most encounters, whereas males with fewer opportunities to reproduce participated less often, hence male participation is influenced by the incentive of maintaining access to females. The number of actively participating individuals in the opponent group positively influenced the participation in both sexes. Thus, sifakas seem to decide joining a given encounter opportunistically, most likely based on a combination of individual incentives and the actual circumstance of each encounter, suggesting that the complexity in intergroup relationships appears to be the product of decisions made by each individual group member.Significance statementCooperation among group-living animals is often challenged by collective action problems resulting from individual differences in interests in contributing to collective behaviors. Intergroup encounters involve distinguished costs and benefits for each individual despite being in the same social group. Therefore, encounters between groups offer a good opportunity to investigate individual participation in collective action. In this study, we investigate the influence of different incentives on individual participation in intergroup encounters in wild Malagasy primate, Verreaux’s sifakas. We propose a novel approach that takes into account the variable circumstances of each conflict, such as the number of individuals fighting in both groups as a predictor for participation. We believe that our study not only provides novel data on wild sifakas, but it also offers new perspectives for the interpretation of intergroup relationships in other taxa.

中文翻译：

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Verreaux's sifakas (Propithecus verreauxi) 中的群体间遭遇：谁打架，为什么打架？


生活在群体中的个体必须采取集体行动才能成功保卫领土。由于相邻群体之间的冲突总是涉及风险和成本，因此个人必须根据对潜在成本和收益之间权衡的评估来决定是否参与特定冲突。由于群体成员参与群体遭遇的动机可能不同，因此他们在冲突中表现出不同程度的参与。在这项研究中，我们调查了影响维罗猴（Propithecus verreauxi）（一种来自马达加斯加的群居灵长类动物）参与群体间接触的因素。在 12 个月的时间里，我们研究了 Kirindy 森林中八个相邻的西法卡族群。我们观察到了已知邻近群体之间的 71 次遭遇，其中成年雌性和雄性参与的频率相同。没有个人参与每一次遭遇，而在较大的群体中，不参与的情况更常见。当女性有抚养婴儿时，她们很少参与冲突，大概是为了降低杀婴的风险。男性参与受到社会地位的影响：占主导地位的男性参与了大多数遭遇，而繁殖机会较少的男性参与的次数较少，因此男性参与受到保持与女性接触的动机的影响。对手群体中积极参与的个体数量对两性的参与产生积极影响。因此，西法卡斯似乎会机会主义地决定加入特定的遭遇，很可能是基于个人动机和每次遭遇的实际情况的结合，这表明群体间关系的复杂性似乎是每个群体成员做出的决定的产物。意义陈述 群居动物之间的合作经常受到集体行动问题的挑战，这些集体行动问题是由于个体在促进集体行为方面的利益差异而产生的。尽管处于同一社会群体，但群体间的遭遇对每个人来说都有着不同的成本和收益。因此，群体之间的接触提供了一个很好的机会来调查个人对集体行动的参与。在这项研究中，我们研究了不同激励因素对野生马达加斯加灵长类动物维罗猴个体参与群体间接触的影响。我们提出了一种新颖的方法，该方法考虑了每次冲突的可变情况，例如两个群体中战斗的人数作为参与的预测因素。我们相信，我们的研究不仅提供了有关野生西法卡斯的新数据，而且还为解释其他类群中的群间关系提供了新的视角。