Have you ever wondered why ants tend to walk in a line?

Have you ever seen a trail of ants? You’ll find all of them walking in the same line almost as if they are following a leader. Most ants do not follow the leader. Instead, they follow a trail of chemical molecules called pheromones. Ants can sense the presence and intensity of these pheromones with their antennae.

When an ant finds food, it deposits these pheromones along the path as it travels back to the nest. Because other ants can sense these pheromones, they too are able to follow this path to the food source. On the way back, pheromones are deposited again re-enforcing the food trail. When eventually the food at the source diminishes, ants stop depositing pheromones and slowly the trail vanishes. Not only do these scent trails enable ants to communicate with each other but it is also an incredibly easy to find your way back home.

But something altogether more interesting happens in desert ants. In the desert where the temperature is so high and the winds so strong, a chemical trail often vaporizes or gets distorted. Ants, like the Saharan Desert Ant, will have to do something more inventive. And their method is quite simple. They appear to be able to count their steps.

Saharan desert ants can use an internal compass and the sun’s angle to identify the direction of home. But how do they know exactly how far? Like us, ants too have standard stride lengths. So simply having a way to track the total number of strides made, rather than actual distance, seems to work.

In 1965, researchers Wolf, Wittlinger and Wehner published the results of an their experiments in a paper titled “The Ant Odometer: Stepping on Stilts and Stumps”. When ants reached a food sources, those researcher took the ants and lengthened their legs by fitting them with tiny stilts. This meant that the ants would now take longer strides. If the made the same number of strides as they had originally counted, they would actually overshoot their nests. And that’s exactly what ants did. Wolk and colleagues followed these experiments with another set – this time surgically shortening the ants’ legs when they reached the food source. As expected, ants tried making the same number of steps as they had taken to get to the source. But because their stride lengths were shorter, they stopped much before reaching their homes.

To date, these experiments are considered landmarks in the study of animal behaviour and cognition. Clearly, their nervous systems were wired in a way that allowed a mechanism of counting. Scientists haven’t yet cracked that neural code.

Ants do not count the way we humans do. They may not have a numerical system like us. But it is apparent they are extremely intelligent using simple ways to adapt to strange places like deserts. As we discover more and more about the animals around us, it seems we will forever be amazed at their ingenious methods.

This feature is from Agastya International Foundation (www.agastya.org), which runs hands-on science programmes for students