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

斑馬身上的條紋是如何形成的？我們很難得到確切的答案。

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.

有些科學(xué)家認為，條紋是一種偽裝的形式，保護斑馬免落獅口。另一些科學(xué)家則認為，條紋在斑馬的求偶儀式中起到關(guān)鍵作用。2014年，有研究人員發(fā)表研究稱，條紋能夠趕走蒼蠅，保護斑馬遠離蒼蠅經(jīng)常傳播的疾病。

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

一項特殊新研究提供了另一種可能的解釋：斑馬的棲息地有時會變得悶熱難耐，條紋能助它們保持涼爽。

"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."

“我們發(fā)現(xiàn)，溫度差異是決定平原斑馬條紋的一個重要因素，”這項研究報告的主要作者，美國加州大學(xué)洛杉磯分校助理研究員布倫達·拉爾松博士在寫給《赫芬頓郵報》的一封電子郵件中說，“季節(jié)性低溫地區(qū)的斑馬，條紋比氣候持續(xù)溫暖地區(qū)的斑馬要少。”

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.

關(guān)于這項研究，研究人員對非洲16個地區(qū)的平原斑馬條紋變化進行了分析。他們?nèi)缓筮€研究了這些條紋圖案與29種環(huán)境變量之間的關(guān)系，包括氣候、捕食和蒼蠅叮咬等。

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.

分析說明了什么？相比其它環(huán)境變量而言，條紋的覆蓋程度與熱氣候關(guān)系更緊密。換句話說，棲息地越熱，斑馬條紋就越多。

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.

《國家地理》雜志報道稱，此種關(guān)聯(lián)的一種假說認為，醒目的黑白條紋能讓斑馬身體周圍的空氣產(chǎn)生對流，從而達到冷卻效果。也就是說，空氣在吸收陽光的黑色條紋上流動得快，而在白色條紋上流動得慢，這樣就會形成冷卻氣流。

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).

的確如此，數(shù)字式測溫槍的初步觀察結(jié)果表明，牧場上斑馬的體表溫度（84.6華氏度）與附近同等大小、褐色毛皮的羚羊（90.5華氏度）相比，明顯較低。

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

但拉爾松認為，這并不意味著斑馬條紋的謎底被最終揭開。

"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."

“我們需要嚴肅對待關(guān)于斑馬條紋的所有假說，”她在郵件中說，“目前尚無法斷定哪一條假說說不通，也沒有任何理由表明答案只有一個。一種動物的特性具有多種功能的例子此前也并非未聽說過。”

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

這項研究發(fā)表在《皇家學(xué)會開放科學(xué)》雜志上。

Vocabulary

zebra: 斑馬

camouflage: 偽裝

repel: 抵制

swelter: 悶熱

habitat: 棲息地

variable: 變量

convection: 對流

preliminary: 初步的

thermometer: 溫度計

antelope: 羚羊

hypotheses: 假定

（譯者：quella0 編輯：許晶晶）