Lemoine Sylvain, Boesch Christophe, Preis Anna, Samuni Liran, Crockford Catherine, Wittig Roman M
Department of Primatology, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
R Soc Open Sci. 2020 May 27;7(5):200577. doi: 10.1098/rsos.200577. eCollection 2020 May.
Territorial social species, including humans, compete between groups over key resources. This between-group competition has evolutionary implications on adaptations like in-group cooperation even with non-kin. An emergent property of between-group competition is group dominance. Mechanisms of group dominance in wild animal populations are difficult to study, as they require long-term data on several groups within a population. Here, using long-term data on four neighbouring groups of wild western chimpanzees, we test the hypothesis that group dominance impacts the costs and benefits of between-group competition, measured by territory size and the pressure exerted by neighbouring groups. Larger groups had larger territories and suffered less neighbour pressure compared with smaller groups. Within-group increase in the number of males led to territory increase, suggesting the role of males in territory acquisition. However, variation in territory sizes and neighbour pressure was better explained by group size. This suggests that the bisexually-bonded social system of western chimpanzees, where females participate in territorial behaviour, confers a competitive advantage to larger groups and that group dominance acts through group size in this population. Considering variation in social systems offers new insights on how group dominance acts in territorial species and its evolutionary implications on within-group cooperation.
包括人类在内的领地性社会物种会在群体之间争夺关键资源。这种群体间竞争对诸如群体内合作（甚至与非亲属之间的合作）等适应性特征具有进化意义。群体间竞争的一个突出特性是群体优势。野生动物种群中群体优势的机制很难研究，因为这需要关于种群内多个群体的长期数据。在此，我们利用野生西部黑猩猩四个相邻群体的长期数据，来检验群体优势会影响群体间竞争的成本和收益这一假设，群体间竞争的成本和收益通过领地大小以及相邻群体施加的压力来衡量。与较小群体相比，较大群体拥有更大的领地且遭受的相邻群体压力更小。群体内雄性数量的增加导致领地扩大，这表明雄性在获取领地方面的作用。然而，领地大小和相邻群体压力的变化用群体大小能更好地解释。这表明西部黑猩猩的双性结合社会系统（雌性也参与领地行为）赋予了较大群体竞争优势，并且在这个种群中群体优势通过群体大小起作用。考虑社会系统的差异为群体优势在领地性物种中如何发挥作用及其对群体内合作的进化意义提供了新的见解。
