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Zebra stripes confuse bloodsucking flies and could inspire anti-bug device

Zebra surrounded with black and white stripes - Moment RF
Zebra surrounded with black and white stripes - Moment RF

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 bothersome bloodsucking horse flies.

Researchers at Bristol University used video analysis to test whether flies were more likely to attack zebra or non-striped horses at a 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.

And the footage revealed why.  While flies slowed down substantially before landing on horses, when they approached zebras they failed to decelerate often crashing into the zebra and ricocheting off, as if they weren’t expecting the animal to be so close.

Professor Tim Caro, Honorary Research Fellow from the University of Bristol’s School of Biological Sciences, said: “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.”

Dr Martin How, Royal Society University 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, the researchers dressed horses up as zebras to see if the effect really was being caused by the stripes and not another reason, such as their smell or behaviour.

Scientists double-checked the results by dressing up a horse as a zebra - Credit: Bristol University 
Scientists double-checked the results by dressing up a horse as a zebra Credit: Bristol University

Just as before, when horses wore coats with striped patterns, they experienced fewer horse fly attacks compared to when they wore single-colour coats.

Horse flies are a widespread problem for domestic animals so developing coats which resemble zebra stripes may offer relief, the scientists conclude.

The research also found that zebra deployed many more tactics to avoid flies, such as running away and swishing their tails at a far higher rate than horses.

Consequently, any horse flies that did successfully land on zebras spent less time there compared to those landing on horses, with few staying long enough to probe for a blood meal.

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, the researchers add.

The research was published in the journal PLOS One.