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Desert ants on their expeditions for food use clues to lead themselves in the homeward direction, but with few landmarks in the poor land, scientists have wondered how the insects always take the most direct route and know exactly how far to march.
The new study shows that counting their steps is an important part of the scheme.
Over the years, scientists have proposed several theories for how ants find their way home.One is that they do it like honeybees and remember visual clues, but experiments showed ants can travel in the dark.Another theory is that because ants run at a steady pace, they could time how long it took them to get to and from.Other studies have shown that once ants find a good source of food, they teach other ants how to find it.
The ant “pedometer” technique was first proposed in 1904, but it remained untested until now.Scientists trained desert ants to walk along a straight path from their nest entrance to a feeder 30 feet away.If the nest or feeder was moved, the ants would break from their straight path after reaching the expected spot and search for their goal.
Try that on stilts.They glued stilt-like extentions to the legs of some ants to lengthen stride.The researchers shortened other ants' stride length by cutting off the ants' feet and lower legs, reducing their legs to stumps.
The ants on stilts took the right number of steps, but because of their increased stride length, marched past their goal.Stump-legged ants, meanwhile, fell short of the goal.After getting used to their new legs, the ants were able to adjust their pedometer.