Fele M, Fürtbauer I, Lurgi M, Papadopoulou M, Bracken A M, Christensen C, O'Riain M J, King A J
Swansea University, Department of Biosciences, Singleton Park, Sketty, Swansea SA2 8PP, Regno Unito.
University of Glasgow, School of Biodiversity, One Health & Veterinary Medicine, 464 Bearsden Rd, Glasgow G61 1QH, Regno Unito.
Behav Ecol. 2025 Mar 11;36(4):araf022. doi: 10.1093/beheco/araf022. eCollection 2025 Jul-Aug.
How individuals in a group move relative to one another can influence both their survival and fitness. Spatial positioning has been well studied in baboons (), which travel collectively in line formations or "progressions." Early studies of baboon progressions presented contradictory findings on the progressions' order - some reporting random positioning of individuals, while others reporting non-random positioning, thought to protect more vulnerable group-members. Here, we revisit this topic and use high-resolution GPS tracking data to study travel progressions in a group of chacma baboon () on Cape Peninsula, South Africa. We identify 78 progressions over 36 d and find that progression orders are not random. We test four non-exclusive hypotheses to explain progression orders: vulnerable individuals position themselves in the middle (risk hypothesis), subordinate individuals position themselves at the front to gain better access to resources (competition hypothesis), dominant individuals assume leading positions (group decision-making hypothesis), or progression order is an emergent outcome of underlying social bonds (social spandrel hypothesis). We find no evidence that progression orders are adaptive responses to minimize an individuals' risk, maximize their resource acquisition, or are the result of decision-makers leading the group. Instead, we find that individuals' positions are predicted by pairwise affiliations, resulting in consistency in order, with more dominant individuals occupying central positions in progressions. This non-random structuring of individuals during progressions can be considered a side-effect or outcome of underlying social forces acting among individuals, providing an example of a "social spandrel" in collective animal behaviour.
群体中个体之间的相对移动方式会影响它们的生存和健康状况。狒狒的空间定位已经得到了充分研究，它们以队列形式或“行进”方式集体行动。早期对狒狒行进的研究在行进顺序上呈现出相互矛盾的结果——一些研究报告个体的定位是随机的，而另一些研究则报告是非随机定位，认为这是为了保护更易受伤害的群体成员。在这里，我们重新审视这个话题，并使用高分辨率GPS跟踪数据来研究南非开普半岛一群东非狒狒的行进情况。我们在36天内识别出78次行进，并发现行进顺序并非随机。我们测试了四个并非相互排斥的假说来解释行进顺序：易受伤害的个体将自己定位在中间（风险假说），从属个体将自己定位在前面以更好地获取资源（竞争假说），占主导地位的个体占据领先位置（群体决策假说），或者行进顺序是潜在社会关系的一种涌现结果（社会附带现象假说）。我们没有发现证据表明行进顺序是为了将个体风险降至最低、使其资源获取最大化的适应性反应，或者是决策者引领群体的结果。相反，我们发现个体的位置由成对关系预测，从而导致顺序上的一致性，更多占主导地位的个体在行进中占据中心位置。在行进过程中个体的这种非随机结构可以被视为个体间潜在社会力量作用的一种副作用或结果，为集体动物行为中的“社会附带现象”提供了一个例子。
