It seems the stripes affect the insects only at very close range, the scientists say, and they suggest zebra-striped coats may be a simple way to protect domestic horses from biting flies.
In 2014, researchers showed the ranges of the horsefly and tsetse fly species and the three most distinctively striped equid species (Equus burchelli, E. zebra, and E. grevyi) overlap to a remarkable degree. But the flies managed to land on zebras less than a quarter as often. While flies slowed down substantially before landing on horses, when they approached.
Study leader Professor Tim Caro, from the University of California at Davis, US, said: "Once they get close to the zebras... they tend to fly past or bump into them".
Flies approach zebras animal with the intention of landing and drinking the zebra's blood.
Martin How, a member of the team from the University of Bristol, says "stripes may dazzle the flies in some way once they are close enough to see them with their low-resolution eyes".
There are several possible explanations as to why zebras have black and white stripes, but a definitive answer remains to be found.More news: Cyclone Oma tracks towards Queensland
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Anti-predation is also a wide-ranging area, including camouflage and various aspects of visual confusion. But what about a zebra's stripes?
In a similar way, human pilots can be dazzled when attempting to land into the sun.
The researchers videoed horse flies as they tried to prey on captive zebras and domestic horses at a livery in North Somerset, England.
The goal of zebra stripes has always been a mystery.
The idea that stripes somehow reduce the likelihood of being bitten by predatory flies has come to be accepted by most scientists, but the exact mechanism remained unclear until recently. The striped animals nearly continuously swish their tails during the day and will stop feeding if they feel bothered.
If the flies are particularly persistent, they will stop feeding or attempt to flee from them. They add, "The selection pressure for striped coat patterns as a response to blood-sucking dipteran parasites is probably high in this region [Africa]", researchers wrote in the journal Experimental Biology.