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The surprising reason why zebras have stripes

The surprising reason why zebras have stripes... 01:38

It's a natural phenomenon that has forever puzzled curious zoo visitors and scientists alike: why do zebras have stripes? Well, the riddle is no more. Scientists finally have an answer.

Researchers at the University of California, Davis, say it's nature's way of protecting them from the bites of blood-sucking flies.

Evolution gave zebras shorter hair than similar species, like horses, leaving them more vulnerable to the wrath of blood-sucking flies, the researchers explained in a press release. Not only are the flies pesky, they also carry deadly diseases. If they were constantly biting, they would be a major risk to the zebras.

But for reasons that are not yet fully understood, the flies that pester large mammals -- usually horseflies and tseste flies -- avoid landing on black and white striped surfaces. And so, by giving them stripes, evolution gave the upper hand back to the zebras.

It's a theory that has been proposed in the past, alongside other hypotheses that suggested perhaps the stripes were a form of camouflage, heat regulation, or a way for zebras to recognize each other.

Research published in February 2012 in the Journal of Experimental Biology also tested the stripes-as-protection conclusion. At the time, scientists from the University of Sweden investigated whether the flies actually avoid the stripes. They concluded that they do, and that zebra stripes are just the right width to deter the flies. Any wider, and the stripes no longer ward off flies, reported Discovery News.

In the UC Davis study, the researchers looked at where horses, zebras and asses live; compared the sizes, color and location of stripes on the zebras' bodies; and considered a few other variables, like the local populations of blood-sucking flies. The results showed that more striped animals lived in areas with larger fly populations.

"I was amazed by our results," said lead author Tim Caro, a UC Davis professor of wildlife biology, in the release. "Again and again, there was greater striping on areas of the body in those parts of the world where there was more annoyance from biting flies."

After more than 120 years of debate, the mystery finally appears to be solved.

"No one knew why zebras have such striking coloration," Caro said. "But solving evolutionary conundrums increases our knowledge of the natural world and may spark greater commitment to conserving it."

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