Why do zebras have stripes? Perhaps to dazzle away flies

The insects didn't slow down as they approached the zebras, "suggesting they did not see the target, or did not regard the striped surface as an appropriate place to land, or were confused somehow by the stripe pattern", the researchers write in a new study published in PLOS One.

There are no flies on a zebra thanks to the evolution of their black and white stripes, according to scientists at the University of Bristol.

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". In Africa, flies called horse flies carry diseases that may seriously harm zebras so they have developed the stripes to protect themselves.

The team said the study showed stripes did not act as a long-range deterrent but had an effect when the flies got up close - possibly because of the flies' low-resolution vision.

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The evolution of the zebra's black & white coat has intrigued scientists for years. Even Kipling would have struggled to construct a Just So story as unlikely as the discovery that the zebra evolved stripes to make flies go splat. It seems the stripes do something that messes with the flies own movement, making it hard to land.

The study noted that zebras and horses respond very differently to the presence of flies. While horses are more low-key about the presence of flies, merely twitching and occasionally swishing their tails to ward off the insects, zebras are far less tolerant. Some thought stripes must help zebras blend into the grasses to avoid lions, which is the worst explanation I've ever heard. Scientists finally (probably) figured out why zebras have stripes. Researchers both watched the animals and filmed them, recording the number of horseflies-which bite animals to obtain blood-that hovered nearby.

"Most biologists involved with research on mammal coloration accept that this is the reason that zebras have stripes". The striped animals nearly continuously swish their tails during the day and will stop feeding if they feel bothered.

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