The use of path integration to guide route learning in ants.

Cataglyphid ants travelling between their nest and feeding site follow familiar routes along which they are guided by views of the surrounding landscape. On bare terrain, with no landmarks available, ants can still navigate using path integration. They continually monitor their net distance and direction from the nest, so that they can return home from any point using their computed 'home vector'. Here we ask whether path integration also provides signals to reinforce the learning of visual landmarks. A fall in the value of the home vector indicates when a homing ant moves in roughly the correct direction, and that it is appropriate to store those views that can guide subsequent trips to the nest. We tested this hypothesis by training the ant Cataglyphis cursor to negotiate a variety of mazes that led from a feeding site back to the nest. Efficient passage of each maze required an ant to discriminate between different pairs of shapes. We show that if the value of the home vector drops while the ant approaches and passes a shape, the shape's appearance is learnt, but if the vector grows, or is absent, no visual learning occurs. Path integration may both help ants navigate through an unfamiliar landscape, and assist them to become familiar with it