D: Do you see that bug over there on the windowsill, Yaël?
Y: How could I miss it, Don? Those bright stripes are visible from miles away. I’m surprised it hasn’t been eaten yet.
D: It might be easy to spot when sitting still, but those stripes could actually be a great strategy when it’s moving—when prey with high-contrast stripes move, their stripes blur, making it hard to a predator to see them. That’s what a group of scientists found out in an experiment on praying mantises. The mantises watched a series of videos that showed rectangular shapes that imitated bugs moving across the screen. Some of the mock bugs had stripes, others had patterns that matched the background, and others had no pattern at all. The mantises moved their heads as they watched the shapes move, as though they were tracking prey. After observing the mantises, researchers found that the mantises found it especially difficult to track the bugs that had narrow stripes and were moving at high speeds. The stripes became blurred, which made the bugs difficult for the mantises to see. Though the experiment was done only on praying mantises watching mock bugs, the researchers think their findings can be applied more broadly to animals in the wild. Though stripes have other uses—for example, zebras’ stripes may help ward off dangerous flies—it’s possible that stripes have the additional benefit of helping animals evade predators if they move fast enough.
Y: Our bug over here doesn’t seem to be taking advantage of that benefit—I haven’t seen it move for the past half hour.
D: Are you sure it’s alive?
Y: Good question.