Even ants can count: to be precise, according to a study, ants Cataglyphis fortis – typical of the Sahara desert – would be able to count their steps. Ants generally go in search of food, leaving a scent trail which they exploit to be able to return to the anthill without getting lost, a bit like Tom Thumb did with breadcrumbs. But there are places on Earth where it is not possible to exploit smell to orient oneself in space. For example in the desert: the heat, together with the sand easily moved by the wind, destroys the scent trails of the ants. This “internal pedometer” of the Saharan ants allows them to know how far they are from their anthill, so that they can then easily find it again.
How Researchers Discovered That Ants Can Count
The researchers linked the anthill and a food supply with a 10 meter metal corridor and waited for the ants to get used to walking back and forth along the corridor to get the food. After a day of training, the researchers “captured” the ants near the food, before they had a chance to return to the anthill, and divided them into 3 groups:
- to the first group have “lengthened” the legs by gluing some microscopic stilts made of very thin pig bristles;
- with the second group were less lenient and have shortened the legs cutting them at the height of the tibia;
- Finally, the legs of the third group have not been modified in any way.
The researchers then placed the ants on a identical corridor to the previous one, but longer and without an anthill.
Normally, when they are near the anthill, the ants change the way they move: instead of proceeding in a straight line, they begin to move back and forth in sudden U-turns at the point where they expect to find the entrance to the nest.
To everyone’s surprise, the ants in the experiment began looking for the entrance at three different heights of the path. The ants with stilts overtook the anthill by about 5 meters, those with shorter legs stopped 5 meters before, and only the ants with normal legs traveled exactly the 10 meters that, in theory, separated them from home.
Why Ants Can Count Their Steps
A logical explanation might be that ants have stored the number of steps to walk between the anthill and the food, and that returning from the food to the anthill they walked the exact same number of steps, but with one big difference: the ants with stilts took longer steps, while those with cut legs took shorter steps. In this way, even walking the same number of steps as the control ants, they covered respectively longer and shorter distances.
But that’s not all. Unfortunately, it’s very difficult to “count” how many steps each ant actually walked. So, to be sure, the researchers did a counter-test. They put each group of ants back into the nest and tested them again a couple of days later. As expected, all three groups were able to reach the food and return precisely to the nest. This suggests that the ants with stilts counted and walked a smaller number of steps, while those with cut legs a larger number.
