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.