Stereoscopic motion analysis in densely packed clusters: 3D analysis of the shimmering behaviour in Giant honey bees.

Gerald Kastberger,Michael Maurer,Horst Bischof,Frank Weihmann,Matthias Ruether,Thomas Hoetzl,Ilse Kranner

doi:10.1186/1742-9994-8-3

Gerald Kastberger, Michael Maurer + Show 5 more

Open Access

https://doi.org/10.1186/1742-9994-8-3

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Abstract

BackgroundThe detailed interpretation of mass phenomena such as human escape panic or swarm behaviour in birds, fish and insects requires detailed analysis of the 3D movements of individual participants. Here, we describe the adaptation of a 3D stereoscopic imaging method to measure the positional coordinates of individual agents in densely packed clusters. The method was applied to study behavioural aspects of shimmering in Giant honeybees, a collective defence behaviour that deters predatory wasps by visual cues, whereby individual bees flip their abdomen upwards in a split second, producing Mexican wave-like patterns.ResultsStereoscopic imaging provided non-invasive, automated, simultaneous, in-situ 3D measurements of hundreds of bees on the nest surface regarding their thoracic position and orientation of the body length axis. Segmentation was the basis for the stereo matching, which defined correspondences of individual bees in pairs of stereo images. Stereo-matched "agent bees" were re-identified in subsequent frames by the tracking procedure and triangulated into real-world coordinates. These algorithms were required to calculate the three spatial motion components (dx: horizontal, dy: vertical and dz: towards and from the comb) of individual bees over time.ConclusionsThe method enables the assessment of the 3D positions of individual Giant honeybees, which is not possible with single-view cameras. The method can be applied to distinguish at the individual bee level active movements of the thoraces produced by abdominal flipping from passive motions generated by the moving bee curtain. The data provide evidence that the z-deflections of thoraces are potential cues for colony-intrinsic communication. The method helps to understand the phenomenon of collective decision-making through mechanoceptive synchronization and to associate shimmering with the principles of wave propagation. With further, minor modifications, the method could be used to study aspects of other mass phenomena that involve active and passive movements of individual agents in densely packed clusters.

Highlights

The detailed interpretation of mass phenomena such as human escape panic or swarm behaviour in birds, fish and insects requires detailed analysis of the 3D movements of individual participants
We studied shimmering in Giant honeybees under field conditions (Figure 1 and 2) in Chitwan (Nepal), with the goal to simultaneously measure the motions of hundreds of surface bees in the three directions of space to obtain a detailed view of the movements of individual bees within the entirety of the bee curtain
We propose a method for the automated identification of individual bees within the densely packed clusters of the bee curtain surface, including the computation of the 3D locations of individual agent bees, following them over time and identifying the arrival of shimmering waves at those agents

Summary

Introduction

The detailed interpretation of mass phenomena such as human escape panic or swarm behaviour in birds, fish and insects requires detailed analysis of the 3D movements of individual participants. Giant honeybee (Apis dorsata) nests [1,2,3,4,5,6,7] constitute a matrix of densely clustered individuals arranged in a multi-layered stratum, the “bee curtain” [8], around a central, flat comb (Figures 1 and 2) Collective behaviours such as mass flight activity and colony defence [7,9] are affected by the functional principles of the 3D architecture of this bee curtain. To avoid unwanted colony arousal, data recording must be non-invasive, keeping a distance of at least 2 m between equipment and nest

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