Automated 3D-image based tracking system
A high-speed stereovision camera (G3 Evo 3, TYZX®) was fixed on the top
of a beehive (10-frame Dadant type) to track the flights of bees and
hornets at the beehive entrance (Figure 1a ). A controller
laptop was used to schedule the recordings and to encode the raw RGB-D
videos before being dumped on a NAS (Network Attached Storage). Video
surveillance was deemed as a robust and effective method to measure the
exact number of honey bees at the entrance of the colony. The
experimental beehive was located nearby the town of La Rochelle (France)
(46°8’N, 1°8’W), 200 km from where the Asian hornet was first spotted in
2004 (Haxaire et al., 2006; Villemant et al., 2011). The video
surveillance was carried out from October 16th to
October 25th 2015. In this oceanic climate, the
ambient temperature ranged between 6°C and 17°C, wind speed ranged
between 11km.h-1 and 39km.h-1, and
the relative humidity ranged between 65 and 82%. Video
tracking was performed from 9am to 6pm over 10 consecutive days,
providing a total of 90 hours of recorded activity, corresponding to
more than a terabyte of compressed data (i.e. RGB-D videos above 50
fps). The monitored beehive was isolated in the apiary (i.e. no other
beehives in a 300m radius) in order to ensure that all observed
trajectories belonged to the target hive. The stereovision camera was
placed 50 cm above the flight board of the beehive to ensure the
non-trivial trade-off between the device intrusiveness (no nearby source
of disturbance), the image definition (at least 8 pixels per bee on the
flight board) and the observed volume (that must include the 50 cm wide
flight board). The Western honey bees (Apis mellifera ) were not
bred from any particular genetic strain, while the native populations
are Apis mellifera melliefra in the region (Requier et al., 2019b) with
common hybridization towards A. mellifera mellifera ×caucasica (Requier et al., 2017). The Asian hornet is present in
high abundance in the region since 15 years (Rome and Villemant, 2022).