They Know the Way? Must Not Be Male Ants

Solved: the mystery of how the ants go marching home.

With nothing but a featureless expanse of sand around them, Saharan desert ants can still calculate the distance to their nest. Now German scientists have figured out that they use a sophisticated internal pedometer.

The ants take a meandering route from their nest in search of food, but when home beckons, they are able to figure the most direct route back.

The researchers, who published their findings Friday in the journal Science, knew the direction component of the ants’ navigation system relied on the sun. But they didn’t know how the ants made their way home.

A team led by neurobiologist Harald Wolf, of the University of Ulm in Germany, hypothesized that the ants essentially counted their steps.

To test their theory, the researchers lengthened the ants’ steps by attaching stilts made from pig bristles to their legs. Amputations left other ants with stumps.

The theory was that, with altered step sizes, the ants with longer legs would go too far in looking for the nest, and the ants with shorter legs would not go far enough.

The results showed just that.

Once they were accustomed to their new legs, the ants adjusted their distance calculations of how many steps it took to get home and behaved just like normal ants.

Now, said Wolf, scientists need to figure out how the ants’ odometer works. That’s the next step.