Can ants count ? It would seem so. They can count their steps, at least, but how high can they go?

In a somewhat surprising article, German entomologists announced last week in the journal Science that ants have a kind of internal pedometer; while they do not count in the way humans do, they are able to retain the number of steps taken since they left home, which makes it easier for them to return.

It has already been shown that certain ant species appear to rely on visual cues to find their way, while others leave scent trails behind them. But the step-counting specie from the Sahara desert is even more remarkable because, as the researchers explain, visual cues are rare in the desert, and scents quickly fade in hot conditions.

In the past, other researchers have hypothesized that ants use the sun as a point of reference. Starting from this theory, Harald Wolf and his colleagues at the University of Ulm in Germany and the University of Zurich in Switzerland deduced that such a point of reference is only useful if the ants have a way to calculate distance. So they took a closer look at the ants' legs and found that ants with shortened legs had trouble finding their way back to the nest.

The same problem was seen with ants whose legs had been lengthened by a millimetre (the scientists glued tiny stilts to their legs). In the latter case, the ants travelled 50 percent too far, walking past the nest before wandering around looking for the entrance.

But though ants cannot really "count"-a point stressed by Wolf, probably concerned about the headlines journalists would use-it is not yet clear what internal system functions as a step counter. The Science article notes one possibility is that the pedometer forms an integral part of the ants' nervous system. But if so, ants are likely not the only animals with such a mechanism. More research is undoubtedly on the horizon.