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

Collective motion describes the global properties of moving groups of animals and the self-organized, coordinated patterns of individual behaviour that produce them. We examined the group-level patterns and local interactions between individuals in wild, free-ranging shoals of three-spine 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 organization within groups. Among the group-level properties reported here, we find that polarization is strongly influenced by group speed, but also the variation in speed among individuals and the nearest neighbour distances of group members. While we find no relationship between group order and group size, we do find that larger groups tend to have lower nearest neighbour distances, which in turn may be important in maintaining group order.

集体运动（Collective motion）指涉动物运动群体的全局特性，以及催生此类特性的个体行为自组织协调模式。本研究针对野生自由漫游的三刺鱼（Gasterosteus aculeatus）鱼群，考察了其群体级行为模式与个体间的局部交互行为。研究数据显示，与目标鱼间距处于1至2个体长的区间内时，近邻相遇频率最高，且在目标个体的侧方位置达到峰值。鱼类与这些侧方近邻的对齐度最高，整体上也与自身前方的个体对齐度更高。此外，相较于更远的同伴，鱼类与近邻在体型、游动速度与朝向的匹配度显著更高，这表明鱼群内部存在局部组织机制。在本次研究报告的群体级特性中，我们发现群体极化（polarization）受群体游动速度的显著影响，同时也受个体间速度差异以及群体成员的近邻距离影响。尽管未发现群体有序度与群体规模存在关联，但我们观测到更大的群体往往拥有更小的近邻距离，而这一因素反过来可能对维持群体有序性至关重要。