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UC Davis Researchers Believe They Now Know Why Zebras Have Stripes

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A young zebra named 'Frauke' stands next to her mother in their enclosure at the zoo in the northern German city of Hanover, (Photo credit DAVID HECKER/AFP/Getty Images)

A young zebra named ‘Frauke’ stands next to her mother in their enclosure at the zoo in the northern German city of Hanover, (Photo credit DAVID HECKER/AFP/Getty Images)

HollyQuan20100908_KCBS_0017r Holly Quan
Holly was born and raised in Oakland and she graduated from San...
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DAVIS (KCBS) – A mystery of the animal kingdom that has baffled scientists for centuries may finally have been solved, according to UC Davis researchers who examined the pests that share the traditional range of the zebra.

It turns out the zebra may sport black and white stripes as a strategy to ward off flies, a not inconsequential problem considering that some flies bite hard enough to draw blood.

“If you’re ever bitten by a horse fly or a deer fly, you’ll know exactly that that’s the problem,” said Tim Caro, a UC Davis professor of conservation ecology.

“Zebras have shorter hair than other antelopes that live next door to them, like impala or buffalo, and that may make them very susceptible to having their skin penetrated by the mouth parts of these flies.”

Caro and his team arrived at their conclusion by overlaying the traditional ranges of the zebra and its related species with locations where biting flies are found.

“We plotted the geographic ranges of all the different species of horses and asses and zebras on maps of the Old World of Africa and Asia,” he said.

“Every time, we find that we get intense striping in areas where they’re really annoyed by biting flies.”

The dark and light bands may also have changed how air flows around the zebra, helping to keep it cool, Caro said, or the striped coat may have provided camouflage against a woodland background, somehow confusing predators or encouraging certain types of grooming by drawing attention to particular areas of the zebra’s body.

But deterring biting flies may be among the most compelling reasons for the success of stripes in the animal’s evolution, according to the study published in the online journal Nature Communications.

“We’re not sure whether these animals are really worried in a (sic) anthropomorphic sense about being bitten by many, many flies and losing lots and lots of blood,” Caro said, “or whether it’s that these flies in Africa carry fatal diseases for zebras.”

The zebra still has some secrets however, such as exactly why or how its stripes discourage flies from landing on it in the first place.

“Flies see the world in a different way than we see the world. They have different eyes, and they can see polarized light, whereas we can’t. And it may be that the hairs of the zebras are giving off different sorts of polarized light,” he said, different from the light given off by the fabric of a t-shirt, for example.

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