Underestimate ants at your own peril.
You may be forgiven for observing ants seeking out food and thinking that their search pattern involves a random, somewhat frantic walk in any-which direction. But new research suggests you’d be wrong.
In fact, a study of the walking patterns of a species of rock ant are the ANT-ithesis of aimless wandering. Scientists from the University of Arizona, Tucson found that the ants intersperse random walks with systematic meandering to create a very orderly search pattern.
“Previously, researchers in the field assumed that ants move in a pure random walk when searching for targets of which they don’t know their location,” says a lead researcher in the study, Dr Stefan Popp. “We found that rock ants, Temnothorax rugatulus, show a striking, regular meandering pattern when exploring the area around their nests. This means that the ants smoothly alternate left and right turns on a relatively regular length scale of roughly three body lengths.”
Popp and his colleagues refer to the behaviour as “meandering”, like the flow of a river as it reaches its final destination.
This meandering, the team believe, may be a more efficient way to cover ground than a purely random search. Crossing their own path less often than if they were tracking randomly means they less often search the same area twice.
Their study shows that 78 percent of the ants exhibited a significant “negative autocorrelation” every 10 millimetres, or about 3 body lengths.
The negative autocorrelation means that turns in one direction were usually followed by a turn in the opposite direction roughly every 10 millimetres. As a result, the ants stay relatively close to the nest while avoiding double up in their search.
It’s hard to track the movements of ants in a colony in the wild. So, Popp’s team moved a whole colony into the lab. There, they could more easily track the ants and control the conditions.
To make sure the meandering pattern they’d noticed wasn’t the result of random walking, the team compared the ants’ trajectories to a statistical model.
In statistics, a random walk can be thought of as a “drunk stagger”. You can step left or right and each step you take has an equal probability (50 percent) of being a leftward step or a rightward one.
“We wanted to make sure that we are not just seeing patterns where there is none,” Popp explains.
The study is another example of complex behaviour in ants. Popp says he is interested in what processes in the ants’ minds allow such complex search patterns to emerge.
How ants evolved search patterns over hundreds of millions of years may inform how we design applications such as autonomous swarms of search robots, or drones used in disaster areas or unexplored landscapes, Popp adds.