VOA慢速英语2019 斑马为何有条纹？（在线收听）

Why Do Zebras Have Stripes?

Scientists have provided new evidence to help solve one of the world’s oldest mysteries: why does a zebra have stripes? It appears that all those lines cause problems for insects and makes it very hard for them to land on the animal.

科学家提供了新的证据来帮助解决世界上最古老的谜团之一：斑马为何有条纹？那些条纹 似乎给昆虫带来问题，使它们很难落在斑马上。

Researchers recently described experiments showing that horse flies have a difficult time landing on zebras while easily landing on horses of a single color.

最近，研究人员称，实验表明马蝇很容易落在单一颜色的马上，却很难落在斑马上。 

In one experiment, the researchers put blankets with stripes on horses and saw that fewer flies landed on them. They “fly past them or …bump into them and bounce off,” said Tim Caro of the University of California-Davis. He was the lead writer of a report on the study. The report was published in the journal PLOS ONE.

在一项实验中，研究人员给马盖上了带有条纹的毯子，发现落在它们身上的苍蝇变少了。这些苍蝇“从马身边飞过，或者......撞到它们身上又反弹飞走，”加州大学戴维斯分校的蒂姆·卡罗说。他是该研究报告的主要撰稿人。该报告发表在《公共科学图书馆·综合》杂志上。

Closely related to horses, the world’s three zebra species are known for their black-and-white striped bodies.

斑马与马是近亲。世界上有三种斑马，它们以其黑白相间的条纹身体而闻名。 

Zebras are native to Africa’s savannas, or grasslands. The design and appearance of the stripes is different from one zebra to the next. No two zebras are alike.

斑马原产于非洲的稀树草原或草地。每匹斑马的条纹图案都是独一无二的。没有两匹斑马是完全相同的。

There had been four main theories about the reasons zebras developed stripes. The first theory is to avoid attack by meat-eating animals. Another is so that zebras have an easier time recognizing other zebras. A third idea is thermoregulation. That is the ability of a creature to control its body temperature, even when the surrounding temperature is different. The fourth theory is to prevent attacks by biting flies.

关于斑马为何进化出条纹主要有四个理论。第一个理论是躲避食肉动物的攻击。另一个是更容易识别其他斑马。第三个理论是调节体温。这是生物控制体温的能力，即使周围温度不同也能保持体温不变。第四个是阻止苍蝇叮咬。

“Only the last stands up…” Caro said. “Most biologists involved with research on mammal coloration accept that this is the reason that zebras have stripes.”

“只有最后一个理论站得住脚......”卡罗说。“大多数参与哺乳动物的自然色彩研究的生物学家都认为这是斑马有条纹的原因。”

African horse flies carry diseases, such as trypanosomiasis. The sickness can cause wasting and be deadly.

非洲马蝇携带疾病，如锥虫病，可能导致虚痨并致命。 

The researchers recorded videos of horse flies as they tried to bite zebras and horses at a farm in North Somerset, England. Stripes did not stop flies from a distance, as they circled horses and zebras at similar rates. But the flies were 25 percent less likely to land on zebras.

研究人员录制了马蝇的视频，在英格兰北萨默塞特的一家农场上，它们试图叮咬斑马和马。条纹并没有阻止苍蝇远离斑马，因为它们以相似的速度盘旋在马匹和斑马周围。但苍蝇落在斑马上的机率较之马匹降低了25％。

University of Bristol biologist Martin How worked with Caro on the study. He said stripes may confuse flies when they get too close to zebras.

布里斯托大学的生物学家马丁·豪与卡罗一起从事这项研究。他说，当马蝇非常接近斑马时，条纹可能会使它们眼花缭乱。

“In addition to stripes that prevent controlled landings by horse flies, zebras are always moving their tail and may frighten off the horse flies if they do land successfully,” How said. He added that zebras are also using behavioral means to prevent flies from biting them.

豪说：“除了其防止马蝇降落的条纹外，斑马总在摆动尾巴，如果马蝇真的落在它们身上，也可能会被吓跑。”他补充说，斑马还使用行为手段来防止苍蝇叮咬。

Words in This Story

mammal – n.a type of animal that feeds milk to its young and that usually has hair or fur covering most of its skin

confuse– v.to cloud; to make something more complex; to identify wrongly

species– n.a classification or grouping of living organisms

stripe– n.a long line that is different in color from nearby areas

blanket– n.a large covering