In animal groups, individual interactions achieve coordinated movements to maintain cohesion. In horse harem groups, herding is a behavior in which males chase females from behind; it is considered to assist with group cohesiveness. However, the mechanisms by which the individuals move to maintain group cohesion are unknown. We applied novel non-invasive methods of drone filming and video tracking to observe horse movements in the field with high temporal and spatial resolution. We tracked all group members and drew trajectories. We analyzed the movements of females and found two phases of interactions based on their timing of movement initiation. The females that moved first were those nearest to the herding male, while the movement initiation of the later females was determined by the distance from the nearest moving female, not by the distance from the herding male. These interactions are unique among animal group movements and might represent a herding mechanism responsible for maintaining group cohesion. This might be due to long-term stable relationships within a harem group and strong social bonds between females. This study showed that the combination of drone filming and video tracking is a useful method for analyzing the movements of animals simultaneously in high resolution.

中文翻译：

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保持后宫凝聚力的羊群机制：羊群中的两个互动阶段

在动物群体中，个体之间的相互作用实现协调运动以保持凝聚力。在马后宫群体中，放牧是雄性从后面追赶雌性的行为；它被认为有助于提高群体凝聚力。然而，个体移动以维持群体凝聚力的机制是未知的。我们应用了无人机拍摄和视频跟踪的新型非侵入性方法，以高时空分辨率观察马匹运动。我们跟踪了所有小组成员并绘制了轨迹。我们分析了女性的运动，并根据她们开始运动的时间发现了两个互动阶段。最先移动的雌性是离放牧雄性最近的雌性，而较晚的雌性则由与最近移动的雌性的距离决定的运动开始，不是与放牧雄性的距离。这些相互作用在动物群体运动中是独一无二的，可能代表了一种负责维持群体凝聚力的羊群机制。这可能是由于后宫群体内长期稳定的关系以及女性之间牢固的社会纽带。这项研究表明，无人机拍摄和视频跟踪的结合是一种以高分辨率同时分析动物运动的有用方法。