Route retracing: way pointing and multiple vector memories in trail-following ants

Abstract

Maintaining positional estimates of goal locations is a fundamental task for navigating animals. Diverse animal groups, including both vertebrates and invertebrates, can accomplish this through path integration. During path integration, navigators integrate movement changes, tracking both distance and direction, to generate a spatial estimate of their start location, or global vector, allowing efficient direct return travel without retracing the outbound route. In ants, path integration is accomplished through the coupling of pedometer and celestial compass estimates. Within path integration, it has been theorized navigators may use multiple vector memories for way-pointing. However, in many instances these navigators may instead be homing via view alignment. Here, we present evidence trail-following ants can attend to segments of their global vector to retrace their non-straight pheromone trails, without the confound of familiar views. Veromessor pergandei foragers navigate to directionally distinct intermediate sites via path integration by orienting along separate legs of their inbound route at unfamiliar locations, indicating these changes are not triggered by familiar external cues, but by vector state. These findings contrast with path integration as a singular memory estimate in ants and underscore the system's ability to waypoint to intermediate goals along the inbound route via multiple vector memories, akin to trapline foraging in bees visiting multiple flower patches. We discuss how reliance on non-straight pheromone-marked trails may support attending to separate vectors to remain on the pheromone rather than attempting straight-line shortcuts back to the nest.

Acute exposure to caffeine improves foraging in an invasive ant

“… 22 However, whether these navigational mechanisms rely on the same neurological foundations, 23 , 24 and the extent to which L. humile rely on these mechanisms remains unclear. Nonetheless, recent work highlights the use of path integration in other trail-laying species 25 , 26 , 27 and L. humile has been shown to be a fast learner of multimodal cues. 28 , 29 , 30 …”