Fig. 1

Mobile Bluetooth Low Energy proximity loggers (0.9 g) (A) used in the experiment, which were protected within a plastic box (35 × 35 × 10 mm) (B) and attached to a neck collar (C)
Mobile Bluetooth Low Energy proximity loggers (0.9 g) (A) used in the experiment, which were protected within a plastic box (35 × 35 × 10 mm) (B) and attached to a neck collar (C)