The interaction of path integration and terrestrial visual cues in navigating desert ants: what can we learn from path characteristics?

Ant foragers make use of multiple navigational cues to navigate through the world and the combination of innate navigational strategies and the learning of environmental information is the secret to their navigational success. We present here detailed information about the paths of Cataglyphis fortis desert ants navigating by an innate strategy, namely path integration. Firstly, we observed that the ants' walking speed decreases significantly along their homing paths, such that they slow down just before reaching the goal, and maintain a slower speed during subsequent search paths. Interestingly, this drop in walking speed is independent of absolute home-vector length and depends on the proportion of the home vector that has been completed. Secondly, we found that ants are influenced more strongly by novel or altered visual cues the further along the homing path they are. These results suggest that path integration modulates speed along the homing path in a way that might help ants search for, utilise or learn environmental information at important locations. Ants walk more slowly and sinuously when encountering novel or altered visual cues and occasionally stop and scan the world; this might indicate the re-learning of visual information.