Scientists from the University of Edinburgh have found that ants use a combination of cues from the sun and visual memories to navigate. When walking backwards to their nest, ants must rely on their memory and the sun’s position to successfully make their way home. The details are in a paper that was just published in the journal Current Biology.
When ants are carrying larger objects, such as big pieces of food, they tend to drag the item while walking backwards to the nest. Previous research had showed that ants use their visual memories to navigate when walking forwards. It would be difficult to rely on memory alone when walking backwards, however, yet ants can successfully navigate for miles this way. This led some scientists to wonder if ants had an alternative means of navigation for situations where they must walk backwards.
A team of researchers observed ants as they walked back to their nest while carrying cookie pieces. The team first located an active desert ant (Cataglyphis velox) nest. The researchers placed underground barriers designed to encourage foraging ants to take the same path out of the nest. The barriers were otherwise not visible to the ants and had no effects on their natural behaviors. Ants were given small or large cookie pieces and each forager was marked with paint so that the team could track the movements of individual insects.
The team found that the ants were using more than just memories to find their way back—the individuals carrying large food items were also relying on cues from the sun. If the researchers tricked the ants by using mirrors to change the appearance of the sun’s position, the insects became briefly disoriented. Interestingly, these same ants would simply turn around and use their visual memories to get back on course. Even when not tricked, foraging ants would periodically put down their finds and look backwards—presumably to make sure they were going the right way. If they were off track, they would then reorient themselves based on their memory of the location. All of the ants were able to use two types of information, sun position and previously formed memories, to navigate backwards.
The findings provide new insights into the navigational abilities of ants. The results are especially impressive because ants have very small brains yet manage to use a combination of memory and visual cues to navigate while walking backwards.
Schwarz et al. How Ants Use Vision When Homing Backward. Current Biology (2017).