A Zebra's Stripes May Not Keep it as Safe as We Thought
If you're a zebra, we have some bad news for you. Stripes, as it turns out, do not confuse predators nearly as much as experts once thought. In fact, their true purpose is still anyone's guess.
A zebra's stripes don't exactly make the animals inconspicuous. On the open plains of Africa, these black and white animals are clear as day, noticeable from miles away even as their primary predators remain well-hidden. So how exactly was it thought this helped?
Experts have long suspected that because zebras travel in groups, their many overlapping striped patterns made it harder for a hunter to tell any one zebra from another. In other words, for a hungry lion, a fleeing mob of zebras would look a lot like a big zigzagging mess of stripes. And if that lion has trouble focusing on one zebra in particular to take down, he and his pride are much more likely to miss out on a meal. (Scroll to read on...)
That, anyways, was the rational, which was even put into practice during both world wars. Geometric pattern paint jobs reportedly made it difficult for enemy artillery crews to judge the distance and speed of allied battleships traveling in tight formation. However, according to a study recently published in the journal Frontiers in Zoology, that 'motion dazzle' effect in nature, as it's been called, isn't nearly as effective as a zebra might like.
For the study, researchers had 60 human participants play a game to test whether stripes influenced their perception of moving targets. The gamers essentially had to 'catch' moving objects on a touch screen by quickly tapping where they were (pictured below). Some of the objects were striped in various ways, while others were a solid gray. They also moved in groups or 'ran' across the screen alone.
"We found that when targets are presented individually, horizontally striped targets are more easily captured than targets with vertical or diagonal stripes," Anna Hughes, a researcher with the University of Cambridge, explained in an emailed statement. "Surprisingly, we also found no benefit of stripes when multiple targets were presented at once, despite the prediction that stripes should be particularly effective in a group scenario." (Scroll to read on...)
So why do zebras boast such noticeable stripes in a predator-filled world?
"Motion may just be one aspect in a larger picture," Hughes added. "Different orientations of stripe patterning may have evolved for different purposes. The evolution of pattern types is complex, for which there isn't one over-ruling factor, but a multitude of possibilities."
According to the researcher, she and her colleague plan next to investigate if perhaps the nature of your average predator's vision system, as opposed to a human one, could be more vulnerable to motion dazzle. Likewise, they aim to see if the stark black and whites of zebras - colors relatively uncommon on an African plains - are the true stars in this show, and not the 'zebra pattern' itself.
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