Maintaining tandem movement cohesion through antennal movements in termites.

How do animals coordinate their motion during migration? Traditional models of movement coordination, for example, describing bird flocks or fish schools, rely on visual interactions. However, many animals are blind, requiring movement coordination through the maintenance of physical contact. The risks and cost of becoming accidentally separated may encourage the evolution of compensatory strategies. Here, we study tandem running in blind termites. We quantitatively investigate how these animals use their appendages to maintain stable pair movements. During tandem runs, male followers use their palps and antennae to maintain physical contact with female leaders. Our posture-tracking analysis revealed that termites dynamically change their antennal movements. Males stabilize their antennae to maintain contact with their partners while their palps are in contact. When the male palps lost contact with a female, males started swinging antennae while increasing movement speed. Antenna removal experiments revealed that antennal swinging contributes to pair maintenance, and males compensate for single antenna loss by increasing the swinging of the remaining one. By providing detailed information on contact-based movement coordination, our results contribute to understanding the diversity of animal collective motion.