斑马条纹到底有何用？

How did zebras get their stripes? It's hard to get a black-and-white answer.

斑马身上的条纹是如何形成的？我们很难得到确切的答案。

Some scientists say the stripes are a form of camouflage that protects zebras from hungry lions. Others say they're key to zebra mating rituals. Just last year, researchers published research suggesting that the stripes repel biting flies, thus protecting the animals from diseases flies sometimes carry.

有些科学家认为，条纹是一种伪装的形式，保护斑马免落狮口。另一些科学家则认为，条纹在斑马的求偶仪式中起到关键作用。2017年，有研究人员发表研究称，条纹能够赶走苍蝇，保护斑马远离苍蝇经常传播的疾病。

But a peculiar new study offers yet another possible explanation: the stripes help the zebras stay cool in their sometimes sweltering habitats.

一项特殊新研究提供了另一种可能的解释：斑马的栖息地有时会变得闷热难耐，条纹能助它们保持凉爽。

"We discovered that temperature is an important predictor of how stripy plains zebra are," Dr. Brenda Larison, an assistant researcher at the University of California, Los Angeles and the study's lead author, told The Huffington Post in an email. "Zebra in areas with seasonal cold temperatures are less stripy than those in areas with sustained warm temperatures."

“我们发现，温度差异是决定平原斑马条纹的一个重要因素，”这项研究报告的主要作者，美国加州大学洛杉矶分校助理研究员布伦达·拉尔松博士在写给《赫芬顿邮报》的一封电子邮件中说，“季节性低温地区的斑马，条纹比气候持续温暖地区的斑马要少。”

For the study, the researchers analyzed variations in the stripes seen in plains zebras at 16 sites in Africa. The researchers then examined the relationship between the stripe patterns and 29 environmental variables, including climate to predation to biting flies.

关于这项研究，研究人员对非洲16个地区的平原斑马条纹变化进行了分析。他们然后还研究了这些条纹图案与29种环境变量之间的关系，包括气候、捕食和苍蝇叮咬等。

What did the analysis show? The extent of striping was correlated more closely with hot weather than with other environmental variables. In other words, the hotter their habitat the more stripes zebras tended to have.

分析说明了什么？相比其它环境变量而言，条纹的覆盖程度与热气候关系更紧密。换句话说，栖息地越热，斑马条纹就越多。

One hypothesis for the correlation is that bold black and white stripes cool zebras by creating convection currents in the air around the animals' bodies. That is, air moves faster over sunlight-absorbing black stripes and slower over white stripes to create cooling airflow, National Geographic reported.

《国家地理》杂志报道称，此种关联的一种假说认为，醒目的黑白条纹能让斑马身体周围的空气产生对流，从而达到冷却效果。也就是说，空气在吸收阳光的黑色条纹上流动得快，而在白色条纹上流动得慢，这样就会形成冷却气流。

Indeed, preliminary observations using a digital thermometer gun showed that grazing zebras maintain a significantly lower surface body temperature (84.6 degrees Fahrenheit) than nearby antelopes that are similar in size but have brown coats (90.5 degrees).

的确如此，数字式测温枪的初步观察结果表明，牧场上斑马的体表温度（84.6华氏度）与附近同等大小、褐色毛皮的羚羊（90.5华氏度）相比，明显较低。

But this doesn't mean the zebra stripes mystery has finally been solved, according to Larison.

但拉尔松认为，这并不意味着斑马条纹的谜底被最终揭开。

"We need to give all the hypotheses for zebra striping serious consideration," she said in the email. "We don't see any of the hypotheses as being out of the running yet and there is no reason to think there has to be just one answer. Multiple functions of a trait are not unheard of."

“我们需要严肃对待关于斑马条纹的所有假说，”她在邮件中说，“目前尚无法断定哪一条假说说不通，也没有任何理由表明答案只有一个。一种动物的特性具有多种功能的例子此前也并非未听说过。”

The study was published in the journal Royal Society Open Science.

这项研究发表在《皇家学会开放科学》杂志上。

Vocabulary

zebra: 斑马

camouflage: 伪装

repel: 抵制

swelter: 闷热

habitat: 栖息地

variable: 变量

convection: 对流

preliminary: 初步的

thermometer: 温度计

antelope: 羚羊

hypotheses: 假定