Visual processing and collective motion-related decision-making in desert locusts

Collectively moving groups of animals rely on decision-making of locally
interacting individuals in order to maintain swarm cohesion. However, the
complex and noisy visual environment poses a major challenge to the
extraction and processing of relevant information. We addressed this
challenge by studying swarming-related decision-making in desert locust
nymphs. Controlled visual stimuli, in the form of random dot
kinematograms, were presented to tethered locust nymphs in a trackball
setup, while monitoring movement trajectory and walking parameters. In a
complementary set of experiments, the neurophysiological basis of the
observed behavioral responses was explored. Our results suggest that
locusts utilize filtering and discrimination upon encountering multiple
stimuli simultaneously. Specifically, we show that locusts are sensitive
to differences in speed at the individual conspecific level, and to
movement coherence at the group level, and may use these to filter out
non-relevant stimuli. The locusts also discriminate and assign different
weights to different stimuli, with an observed interactive effect of
stimulus size, relative abundance, and motion direction. Our findings
provide insights into the cognitive abilities of locusts in the domain of
decision-making and visual-based collective motion and support locusts as
a model for investigating sensory-motor integration and motion-related
decision-making in the intricate swarm environment.