Visual navigation in ants while walking backwards

Animals walk for carrying out several tasks such as foraging, escaping predation, mating, and migration. Navigating animals need a compass to know where to go and typically they travel by facing the direction of the goal. For this, they rely on several compass cues such as terrestrial, celestial, olfactory, geomagnetic and wind cues. However, there are some instances like backward walking, where animals move not facing the goal direction, as observed in ball-rolling dung beetles, solitary foraging wasps and ants. Ants walk backwards when they must transport a heavy item, which they cannot lift and walk forwards. Backward walking has been previously described in Cataglyphis and Myrmecia ant species and they have been found to use both terrestrial and celestial cues. Here, I attempted to identify the compass cue used by the Rhytidoponera sp. ants to set their initial heading directions towards the nest while walking backwards. Filming these ants at their familiar and unfamiliar locations clearly showed that the initial heading directions are set in the direction dictated by the celestial compass while walking backwards.