Data from: Local interactions and global properties of free-ranging stickleback shoals

Collective motion describes the global properties of moving groups of animals and the self-organised, co-ordinated patterns of individual behaviour that produce them. We examined the group-level patterns and local interactions between individuals in free-ranging shoals of threespine sticklebacks, Gasterosteus aculeatus. Our data reveal that the highest frequencies of near neighbour encounters occur at between one and two body lengths from a focal fish, with the peak frequency alongside a focal individual. Fish also show the highest alignment with these laterally placed individuals, and generally with animals in front of themselves. Furthermore, fish are more closely matched in size, speed and orientation to their near neighbours than to more distant neighbours, indicating local organisation within groups. Among the group-level properties reported here, we find that polarisation is strongly influenced by group speed, but also the variation in speed among individuals and their nearest neighbour distances of group-members. While we find no relationship between group order and group size, we do find that larger groups, faster groups and those exhibiting lower variance in speed tend to be more densely packed, which in turn may be important in maintaining group order.群体运动（Collective motion）描述了动物运动群体的全局属性，以及催生这些属性的个体行为自组织、协同模式。本研究针对自由巡游的三刺鱼（Gasterosteus aculeatus）鱼群，分析了其群体层面的行为模式与个体间的局部交互。研究数据显示，目标个体鱼的近邻相遇频率峰值出现在距离自身1至2个体长的范围内，且在侧方位置的相遇频率达到顶峰。目标个体与侧方位置同伴的朝向对齐程度最高，总体上也与自身前方的个体对齐更佳。相较于距离更远的同伴，目标个体与近邻个体在体型、移动速度与朝向取向的匹配度更高，这表明鱼群内部存在局部组织机制。在本次研究报道的群体层面属性中，我们发现群体极化（polarisation）显著受群体移动速度、个体间速度变异度以及群体成员最近邻距离的共同影响。尽管未发现群体有序性与群体规模间存在显著关联，但我们观察到规模更大、移动更快且速度变异度更低的鱼群往往更为密集，而这种群体密集性反过来可能对维持群体有序性具有关键作用。