Horses Wearing Striped Pajamas Shed Light On How Zebras Avoid Biting Flies


Scientists explain the reason behind the zebra's unique stripes in new research that demonstrated findings by dressing horses up in the animal's tell-tale pattern.

Why Do Zebras Have Stripes?

For many years, researchers have wondered why zebras sport their very noticeable stripes. There were several possibilities, including protection from predators and cooling mechanisms, among others.

None of these reasons ever held up to scientific scrutiny, except one: protection against flies.

Zebras are extremely vulnerable to insect attacks, not just because of their short hairs that make it easy for flies to find and latch onto blood vessels, but also because of their susceptibility to fatal diseases transferred by horseflies and tsetse flies, according to a report from The Atlantic.

Stripes help protect the zebras from these attacks. In fact, a recent study revealed that even humans can benefit from zebra stripes.

Testing Horses And Zebras

In a new study published in the journal PLOS ONE, Tim Caro and his team demonstrated the relationship between stripes and flies by closely observing nine single-colored horses and three captive plains zebras.

Results showed that the horses and zebras had a similar number of flies approach them, likely due to the flies getting attracted to their smell and their inability to detect the stripes from afar, Caro points out in an article penned in Discover Magazine.

However, flies only landed on the zebras at one-fourth of the rate they landed on the horses, according to Science Magazine. In over five hours of observation, none of the flies that landed on zebras even pierced the animals' skin. On the other hand, flies were able to bite the horses 239 times within an 11-hour period.

Video recordings showed that flies either flew past the zebras or collided and bounced off them instead of decelerating and landing.

The scientists also clothed seven of the horses in three differently colored cloaks: a plain black cloak, a plain white cloak, and an irregularly striped black and white cloak that mimicked a zebra's coat.

Within a 30-minute observation period, only five flies landed on the horses dressed in zebra coats, while over 60 flies landed on the ones dressed in plain cloaks.

Many of the details about zebra's incredible ability to repel flies remain inconclusive for now. There could be a multitude of reasons why stripes prevent flies from attacking the unique animal.

Paloma Gonzalez-Bellido of the University of Minnesota tells The Atlantic that she thinks the inconsistencies in zebra stripes make it challenging for flies to gauge and control their landing.

Caro and his team are already looking ahead to the different ways they can study the relationship between zebra stripes and fly behavior.

"Now that we know striped coats work just as well as stripes on real zebras, we can really play around with them," he says in The Atlantic. "We can put on coats with very wide stripes, or different orientations, or gray stripes. We can see how those affect fly behavior."

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