Why zebras have stripes

There have been many theories to explain the zebra's unmistakable無誤, 不會錯的 stripes. Scientists have suggested that each zebra has a unique獨特的 pattern模式 that lets other animals recognise it. Or that the mass of black and white in a vast廣大的 herd群 provides confusing camouflage偽裝 that puts off predators肉食動物.

But this team set out to test exactly what effect the stripes had on a zebra's most irritating惱人的, 刺激性 and ubiquitous普遍的 enemy - the blood-sucking horsefly吸血虻.

As part of their experiment the team put sticky horse models - one white, one black and one zebra-striped - into a fly-infested field. When they collected the flies that had landed and stuck to each of the models, they found that the model zebra attracted by far the fewest最少的 flies.

The researchers think that zebras had a black-coated ancestor祖先, which evolved進化 its white stripes in an evolutionary進化的 arms race, with an insect that's become the biting, disease-carrying scourge災難 of most horse herds.

this text is from bbc learning english

http://www.bbc.co.uk/worldservice/learningenglish/language/wordsinthenews/2012/02/120210_witn_zebra_story.shtml