Summary: Merkle & Wehner (2009)

Foraging desert ants, Cataglyphis fortis, do not rely on chemical cues when searching for their nest, but rather navigate using path integration. In this process, all directions steered and covered for all movements are summed, providing ants with a home vector that leads them back to the nest on a straight path. Ants also use landmark information to adjust their movements as the path integrator is prone to error. Ants engage in systematic search behaviour if they do not encounter the nest entrance at the position suggested by the path integrator. Merkle & Wehner (2009) investigated whether additional cues influence the systematic search patterns of desert ants or whether this is exclusively determined by distance travelled. They captured ants at different points during inbound journeys or when about to enter the nest. Ants were then transferred to an unfamiliar test area and their paths recorded. Merkle & Wehner (2009) found that searches were influenced by distance covered, as well as other factors, but certainty of nest location increased with closeness to the nest. Most inbound ants, regardless of distance, continued the remaining part of their runs and then commenced their nest search, whereas those captured at the nest entrance started searching for the nest immediately. They suggest that the ants' systematic search behaviour does not depend only on the length of the foraging trip, but is more flexible than previously thought.