Homeward navigation in Pogonomyrmex occidentalis harvester ants

Abstract

This study determined the relative importance of sources of navigational information in Pogonomyrmex occidentalis harvester ants. Displacement experiments, polarized light manipulations, and view manipulations tested the use of path integration, polarized light patterns, and visual guidance in the ability of Pogonomyrmex ants to orient homeward during foraging. In the displacement experiments, worker ants that were displaced from their original locations to new locations equidistant from the nest initially walked in the direction of the home vector that would be determined by a path integrator (PI). Sham treatments showed that handling and returning ants to their original location had no effect on homeward navigation. Neither a polarizing filter nor changing nearby landmarks affected orientation. However, placement of a wall behind the nest while an ant was navigating homeward caused it to become disoriented. Ants viewing the wall walked in random directions and took more time to find their nest. These results suggest that P. occidentalis workers rely on PI to navigate homeward after foraging, but do not follow the home vector indicated by the PI if the panorama has been significantly altered and, therefore, conflicts with the available PI information.