Data from: Are 2D space-use analyses adapted to animals living in 3D environments? A case study on a fish shoal

Methodologies enabling the monitoring of animal movement and behavior in 3-dimensions (3D; x, y, z, the latter accounting for the vertical dimension) are becoming increasingly accessible and can be deployed on entire groups of animals inhabiting 3D habitats. When 2-dimensional (2D; x, y) space-use analyses are used on such groups, their spatial organization is represented as a planar projection of individuals’ space-use. Movement on the vertical dimension is ignored and could biased ecological inference made from the spatial structure of the group. We used a digital imaging technique to track movements and feeding behavior of individual animals within a free-range aggregation of juvenile drift-feeding fish (Galaxias anomalus) in 3D and at fine spatiotemporal scales. We estimated spatiotemporal overlap of space-use and feeding territories between group-members using 2D (x, y) and 3D spatial analysis to: (1) describe the spatial structure of the group, (2) identify patterns of resource partitioning, and (3) investigate the relationship between space-use overlap and feeding behavior. We found that overlapping ratios of space-use and feeding territories were over-estimated in 2D, while 3D analysis of space-use provided evidence of spatial partitioning between group-members. We also found that, regardless of the computation used, the overlapping ratios of space-use were positively correlated with overlapping ratios of feeding territories while no effect was found on feeding activity. In conclusion, whilst 3D analysis provided valuable information on the spatial structure of a group, inferences on the ecological function of space-use can also be obtained from 2D analysis.

可实现三维（3-dimensional，3D；x、y、z三轴，其中z代表垂直维度）环境下动物运动与行为监测的方法，其可用性正不断提升，且可应用于栖息于三维生境中的全部动物类群。当针对此类类群采用二维（2-dimensional，2D；x、y轴）空间利用（space-use）分析时，类群的空间组织会被表征为个体空间利用的平面投影，而垂直维度上的运动则被完全忽略，这可能会对基于类群空间结构得出的生态学推论造成偏倚。本研究采用数字成像技术，在精细时空尺度下对自由聚集的幼年期漂流食性鱼类（Galaxias anomalus）群体内的个体运动与摄食行为进行追踪。本研究分别采用二维与三维空间利用（space-use）分析方法，估算类群成员间的空间利用与摄食领地（feeding territory）时空重叠度，以达成三个研究目标：（1）描述类群的空间结构；（2）识别资源划分模式；（3）探究空间利用重叠度与摄食行为之间的关联。研究结果显示，二维分析会高估空间利用与摄食领地的重叠比率，而三维空间利用分析则为类群成员间的空间分隔提供了实证依据。此外，本研究还发现，无论采用何种计算方式，空间利用重叠度均与摄食领地重叠度呈显著正相关，但未发现其对摄食活动存在显著影响。综上，尽管三维分析可为类群空间结构提供极具价值的信息，但基于二维分析同样可得出有关空间利用生态学功能的推论。