Reversing Ants Often Walk Backwards
The desert ant, nicknamed the "reversing ant," can navigate backyard just as well as it moves forward.
People and many other animals can move backwards, however awkwardly, but the desert ant -- nicknamed the "reversing ant" -- can navigate like this just as well as it moves forward, finds new research that also identifies the ant's surprising technique.
The spindly-legged desert ant (Cataglyphis fortis) actually measures the length of each stride that it takes, allowing it to keep track of its location at any point, according to the paper, published in the Journal of Experimental Biology.
The ability allows the ants to drag food that is much heavier than them over long distances back to their nests.
"They are really awesome," co-author Matthias Wittlinger from the University of Ulm said in a press release. "All the cues are from the other direction."
Wittlinger and colleagues Verena Wahl and Sarah Pfeffer traveled to the Tunisian desert to study the ants. It was not too hard to lure them, especially with "colossal" cookie crumbs weighing 10 times more than each ant.
When the ants encounter that kind of treat, it's as if "they say, 'Wow, there is a large food item. Let's get home," Whittlinger said.
He and his team filmed the ants with a high-speed camera and recorded that the reversing ants walked at about the same step rate as when they moved forward. Each leg, however, was moving on its own, versus the "tripod gait" of always keeping three legs in contact with the ground as the other three swing forward, which is what the ants use when moving forward.
They go backwards "by faster swings and they often use leg combinations where more than three legs have ground contact to increase their static stability," Pfeffer explained.
The researchers said that the ants could be using one of two methods to measure the length of each stride. The first is that they might utilize a copy of their brain motor signals and subconsciously add them up to calculate a distance.
The second possibility is that they measure the length of each stride or leg swing.
Because the ants know precisely how far they travel, even though each leg moves individually, Wittlinger said, "The data suggest it is the second hypothesis."
It's still a mystery as to what exact cues the ants are using to so skillfully navigate their environment. Are they following odors, visuals and/or perhaps signals from something else? The answers, if determined, could some day be applied to man-made tech.
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