War on flies is where zebras earn their stripes

Rudyard Kipling supposed the zebra acquired its stripes so it could blend into the forest shadows, hidden away from the leopard and man.

But the markings also hold another advantage, scientists have discovered, after finding they disorientate bloodsucking horse flies.

Researchers at the University of Bristol used video analysis to test whether flies were more likely to attack zebras or horses at stables in North Somerset. They found that although flies circled and touched horses and zebras at similar rates, they actually landed on zebras 25 per cent less often. The video footage revealed why.

While flies slowed down substantially before the landed on horses, when they approached zebras they failed to decelerate, often crashing into the zebra and then ricocheting off, as if they were not expecting the animal to be so close.

‘‘Horse flies just seem to fly over zebra stripes or bump into them, but this didn’t happen with horses. Consequently, far fewer successful landings were experienced by zebras compared to horses,’’ Professor Tim Caro, an honorary research fellow at the university’s School of Biological Sciences, said.

Dr Martin How, a Royal Society research fellow in the School of Biological Sciences, added: ‘‘This reduced ability to land on the zebra’s coat may be due to stripes disrupting the visual system of the horse flies during their final moments of approach. Stripes may dazzle flies in some way once they are close enough to see them with their low-resolution eyes.’’

In a second experiment, researchers dressed horses as zebras to see if the effect was being caused by the stripes and not another reason, such as smell or behaviour. When horses wore coats with striped patterns, they experienced fewer fly attacks compared to when they wore single-colour coats.

In Africa, where zebras are native, horse flies carry dangerous debilitating diseases such as trypanosomiasis and African horse sickness, which cause wasting and often death, so the development of stripes may be a direct result of the lethal threat, researchers said.

The research was published in the journal

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‘‘Stripes may dazzle flies in some way once they are close enough to see them with their lowresolution eyes.’’

Dr Martin How

AP In this undated photo issued by University of Bristol, England, showing a horse wearing a zebra striped coat. Scientists from the University of Bristol and the University of California at Davis, dressed horses in blackand-white zebra type striped coats for part of their research, offering evidence that zebra stripes provide protection from blood-sucking insects that spread diseases.