Why does a zebra have stripes? 斑马为何有斑纹？

Victoria Gill, BBC News

White stripes could have been a result of natural selection

媒体英语会带大家一起学习 BBC 撰稿人在报道世界大事时常用到的单词和短语。

科学家们称他们已经揭开了斑马身上为何有黑白条斑纹的秘密。这篇刊登在《自然生物学期刊上》的文章说斑纹有掩护作用，因为昆虫不喜欢斑纹。

There have been many theories to explain the zebra's unmistakable stripes. Scientists have suggested that each zebra has a unique pattern that lets other animals recognise it. Or that the mass of black and white in a vast herd provides confusing camouflage that puts off predators.

But this team set out to test exactly what effect the stripes had on a zebra's most irritating and ubiquitous enemy - the blood-sucking horsefly.

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 flies.

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