How desert ants navigate walking backward

Foraging species like Cataglyphis velox and Myrmecia piliventris (shown) use celestial cues and visual memory to walk backward — helpful when dragging a big dinner home.

AJAY NARENDA

Some ants are so good at navigating they can do it backward.

Researchers think that foraging ants memorize scenes in front of them to find their way back to the nest. But that only works when facing forward. Still, some species have been observed trekking in reverse to drag dinner home.

To find out how the ants manage this feat, Antoine Wystrach of the University of Edinburgh and his colleagues captured foraging desert ants (Cataglyphis velox) near a nest outside Seville, Spain. In a series of tests, they gave the ants cookie crumbles and released them at a fork in the route back to their nest.

With cookie chunks in tow, ants walking backward used cues from the sky to maintain a straight path. They also peeked behind them to check and adjust course. Regardless of their body orientation, ants maintained this new direction. Desert ants combine their celestial compass and long-term visual memories of the route to find their way home