How the desert ant Cataglyphis fortis uses its nest hill for homing

The desert ant Cataglyphis fortis relies on path integration and environmental cues for navigation. In featureless environments, nest hills serve as landmarks that enhance homing success. We found that homing ants can discriminate their own nest hills from others based on visual cues. When, as a result of experimental displacement, the path integrator points towards a foreign nest, the ants compare visual cues from the perceived nest hill with their memory and continue approaching only if the hill size does not deviate markedly from the memorised one. Homing ants that mistake a foreign hill for their own climb it, indicating that the hills do not provide nest-specific contact cues. However, near the nest entrance in the centre of the volcano-shaped hills, nest-specific cues circumvent the risk of ants entering the wrong nest, where they would be killed. These findings demonstrate the integration of different modalities that enable ants to optimise their homing.