Landmark cues can change the motivational state of desert ant foragers

Desert ants of the genus Cataglyphis rely on path integration vectors to return to the nest (inbound runs) and back to frequently visited feeding sites (outbound runs). If disturbed, e.g., experimentally displaced on their inbound runs, they continue to run off their home-bound vector, but if disturbed in the same way on their outbound runs, they do not continue their feeder-based vector, but immediately switch on the home-bound state of their path integration vector and return to the nest. Here we show that familiar landmarks encountered by the ants during their run towards the feeder can change the ants' motivational state insofar that the ants even if disturbed continue to run in the nest-to-feeder direction rather than reverse their courses, as they do in landmark-free situations. Hence, landmark cues can cause the ants to change their motivational state from homing to foraging.