A desert ant in the Sahara finds its way home across flat, featureless sand partly by counting. In 2006 a team in Germany and Switzerland let ants walk out to a feeder about ten metres from the nest, then, before the walk home, glued pig bristles to some ants’ legs as stilts and trimmed others’ legs to stumps. The ants on stilts marched straight past the nest and started searching beyond it; the ants on stumps stopped short. Neither was lost. Each had taken the right number of steps for the trip out, with legs that were no longer the legs it had counted with. When the researchers let the altered ants make the whole trip out and back on their new legs, they got home fine. The counting itself never failed. It only misled them when the thing doing the counting had changed halfway through, and nobody told it.