Evidence for homing behaviour consistent with path integration in Dascyllus trimaculatus

Path integration is a strategy that allows animals to monitor their movement relative to a starting point using directional and distance cues. It has been observed in a wide range of terrestrial species, but evidence of this behaviour in fish is still lacking. In contrast to most animals shown to navigate via path integration, fish are not surface bound but exist within a three-dimensional medium. This may present additional challenges when monitoring their position relative to a specific point. We developed a novel experimental paradigm to test whether the coral reef-dwelling domino damselfish Dascyllus trimaculatus could use path integration to navigate back to a shelter location. This consisted of a circular pool with a shelter and landmarks near the edge and a trap containing food in the centre. Our results show that these fish follow homing trajectories back to the previous location of the removed shelter without using landmarks after a foraging trip into the central trap. Error in homing trajectory increased with outward path length, consistent with the use of path integration. These results add D. trimaculatus to the growing list of path-integrating species, opening new avenues for investigating the evolution and neural underpinnings of this navigational strategy.