A Method for Visual Psychophysics based on the Navigational Behaviour of Desert Ants (Melophorus bagoti)

The Australian desert ant Melophorus bagoti is known to navigate in their complex visual environment relying on path integration and landmark learning. We investigated the navigational behaviour of desert ants in response to visual stimulus changes along their route to a food source. Ants were trained to self navigate a track between their nest and a feeder, with visual stimuli introduced near the feeder. After three days of training, we altered the visual scene by changing colours and observed the ants reactions. The results showed that ants in the test conditions, when visual changes were introduced, displayed more meandering paths, increased scanning behaviour, and slower speeds compared to control conditions. The sinuosity of their paths increased, and their orientation became less efficient. Additionally, changes in colour led to significant alterations in path characteristics, including a higher frequency of head oscillations and deviations from straight-line paths. These findings suggest that disruption to visual cues used for navigation causes noticeable changes in their movement patterns. A subset of these changes, easy to measure and calculate, can provide a signature to indicate that ants have detected a change in the visual stimuli. This proof of concept study thus highlights a method for studying visual psychophysics in ants in their natural habitat.