“How did zebras get their stripes?” is an age-old question that has vexed scientists and children’s book authors for years. But an even older question, asked by humans and our primate forbears long before we were even here is: “How do I get these damn flies to stop biting me?”

It turns out—and it’s here I’d like outdoor apparel makers to pay extra close attention—the answers to those questions may be related.

A recent study published in the science journal PLOS ONE argues that a zebra’s stripes evolved to protect them from biting flies and other nasty, annoying pests of the flying and biting variety. First, the article picks apart the classic explanations of the stripes. Camouflage? Nope, say the scientists. For one thing, we can spot zebras instantly in the field—they stick out like, well, a black-and-white striped horse in a field of green grass. Plus, animals that eat zebras, including lions and hyenas, can’t see well enough at a distance to discern stripes until they were already chasing down the zebras. Plus, you know, they eat zebras all the time, which suggests the stripes suck as camouflage anyway.



Those squiggly lines mark fly approaches. As you can see, the zebras were a no-fly zone.

Some say stripes help zebras tell each other apart, but unstriped horses don’t have trouble recognizing each other. Or maybe they help keep the animals cool? Nah, say the scientists, after coating water barrels with striped and unstriped hides, letting them heat in the sun, then noting the temps were the same regardless of the presence of stripes.

But, there was one area in which the stripes made a really big difference. The fly biting part.

Scientists who performed the study, led by Tim Caro, a wildlife biologist at the University of California, Davis, and Martin How of the University of Bristol, noticed that the most striped members of the equid species, including zebras and the African wild ass, lived in places with swarms of annoying horseflies, many of which carry deadly diseases. Acting on that assumption, they performed experiments.



Horses dressed like this received much less unwanted attention from biting flies than their naked companions. Photo: CC

Working on a horse ranch and mixing a group of zebras and plain-old horses, they recorded which animals were more likely to get bitten by flies. Horses had the flies hover over them, then alight on the uniformly colored animals for a blood snack. But the flies seemed to just bump full speed into the zebras and bounce off, as if they hadn’t even seen the zebras. They even tossed striped coats over horses and noted that the horses were still bitten on the head, but the flies ignored the striped areas.

Why? Good question. Could be that the stripes interrupt the vision of the flies and they don’t recognize the zebras as solid bodies and try to fly through them. Or maybe they just get confused by the stripe pattern and can’t figure out how to land. Either way, that part of the study is next.

Frankly, it doesn’t really matter why it seems to work, the real question is: Can apparel companies start making outdoor sports clothes in striped patterns? Please? DEET is nasty, picaridin can’t be any better, and natural oil-based mosquito and fly repellents don’t really work. And biting flies are horrible to deal with. Ever been to New Zealand in the summer and dealt with their maddening sand flies? Bitten by a horsefly or a deer fly? Heinous, heinous annoyance.

Until outdoor brands get on board, I may start dressing like a Foot Locker employee when I venture into biting fly territory in the backcountry this summer. Can’t hurt.


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