Why Do Zebras Have Stripes?

To protect against bloodsucking flies

These stripes have a purpose, no butts about it. (Getty Images)

What do you call a horse wearing Venetian blinds? A zebra. Because of the stripes. Get it? But those stripes aren't just for decoration. New research from the University of California, Davis finds that they serve as a defense mechanism, the Guardian reports. 

The study, published this week in Nature Communications, found that the zebra's stripes deter bloodsucking ectoparasites such as tsetse flies and horseflies, which transmit often-fatal diseases to horses and are probably also capable of draining large amounts of blood.

Researchers studied the geographical distributions of the seven different living species of zebras, horses, and asses, including 20 subspecies found in the Old World, and found that striped species such as the zebra often live in the same region as biting flies.

"I was amazed by our results," lead author Tim Caro, a UC Davis professor of wildlife biology, told the Christian Science Monitor. "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."

The study refuted previous theories for the purpose of the stripes—some dating back to Charles Darwin—that attribute the stripes to aiding camouflage, heat management, or social interaction.

Why don’t bloodsucking flies like stripes? Several studies dating back to the 1930s have shown that flies prefer to land on all-black or all-white surfaces rather than on stripes, but more recent research is needed for scientists to know for sure.

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