好英语网为什么大熊猫喜欢在马粪里打滚？
Last Wednesday, Aleah Bowie, a wildlife ecologist and animal behavior expert, received an interview request by email that made her do a serious double take.
上周三，野生动植物生态学者、动物行为学专家阿莱娅·鲍伊(Aleah Bowie)收到了一封邮件发来的采访请求，这个请求让她不由得一怔。
Attached to the message was a peer-reviewed scientific paper by a team of Chinese scientists who had dedicated more than a decade to investigating why giant pandas smear their bodies with mounds and mounds of horse manure.
邮件的附件是一份经过同行审议、由一队中国科学家撰写的科学论文，这群科学家花费十多年时间来研究为何大熊猫会把一堆堆马粪抹在自己身上。
“I was like, ‘Is this spam?’” Dr. Bowie, of Duke University, said.
“我当时心想，‘这是垃圾邮件吗？’”杜克大学的鲍伊博士说。
But it really is something that the charismatic mammals will do in the Qinling Mountains in China. The bears sniff out fresh horse droppings, lay themselves down and roll their bulky bodies in the muck, using their paws to really make sure they are covered from the tip of their fuzzy ears to the bottom of their tails, until their black and white fur is another shade entirely.
但这的确是生活在中国秦岭的那些招人喜爱的哺乳动物会做的事情。大熊猫能嗅出新鲜马粪，然后躺下，笨重的身躯在污物中打滚，用爪子确保自己从毛绒绒的耳朵尖到尾巴都能抹上马粪，直到黑白分明的毛皮完全变成另一个颜色。
The behavior may help the pandas tolerate cold temperatures because a compound in horse dung, the researchers propose in the paper published Monday in the Proceedings of the National Academy of Sciences, may short-circuit a cellular thermostat that makes pandas sensitive to chill.
这篇论文周一发表于《美国国家科学院学报》(Proceedings of the National Academy of Sciences)，研究人员在其中提出，这种行为也许能帮助大熊猫忍受寒冷，马粪中的某种成分可能导致某种体温调节细胞短路，而这种细胞原本会让大熊猫对寒冷敏感。
Horses and pandas aren’t necessarily natural partners, as their habitats don’t often overlap. But a rich history of domestication by humans has made horses a relatively common fixture in some of China’s forested wilds, where pandas live. Where the horses go, so go their droppings.
由于生活环境没有重叠，马和大熊猫并非天生的伙伴。但人类驯养马的漫长历史让这种生物成为了中国的野外森林中较为常见的物种，而森林也是大熊猫的栖息地。有马的地方，就有马粪。
A team of researchers led by Fuwen Wei, a biologist at the Chinese Academy of Sciences, first noticed a panda luxuriating in a pile of horse excrement in 2007. Unsure of whether it was a fluke, they spent years tracking the bears with dozens of camera traps, eventually convincing themselves that the behavior was “definitely frequent and typical,” Dr. Wei wrote in an email. Between July 2016 and June 2017 alone, 38 instances were documented, each typically characterized by a series of calculated steps.
2007年，中国科学院生物学家魏辅文领导的科研小组首次注意到一只熊猫在一堆马粪里快活的样子。由于不确定是否属于偶然现象，他们花费多年用数十个相机陷阱（即动物触发传感器后会启动的摄像机——编注）追踪这些大熊猫，最终认定，这种行为是“绝对常见且典型”的，魏辅文在一封邮件中写道。在2016年7月到2017年7月期间，他们记录下了38起类似行为，每一次都明显具有一系列精心安排的步骤。
Drawn to the irresistible stink of the droppings — the fresher the better — the bears would first take a careful whiff, then initiate a gentle rubbing with a cheek. They would next immerse themselves in an unbridled full-body tussle in the dung, before meticulously slathering themselves with their paws to ensure all their exposed bits were covered.
受到马粪诱人的臭味所吸引——越新鲜越好——大熊猫首先会小心地闻一闻，然后开始轻轻在脸上摩擦。它们接下来会肆无忌惮地把全身在马粪里扭动，然后仔细地用爪子大量在身上涂抹，确保所有暴露在外面的地方都被盖住。
Plenty of other animals have been recorded fondling feces for a variety of reasons, whether using them to mark their territories or snarfing them as snacks. But it’s a bit unusual to pilfer the poop of another species; it’s even weirder to lather it up on the regular.
许多动物出于各种原因喜爱粪便，不管是用它标记领地，还是将其狼吞虎咽地作为零食。但将另一种动物的粪便偷来略为不寻常，经常性把粪便抹遍全身就更奇怪了。
“There are all kinds of reasons you want to stay away from feces,” Dr. Bowie said. She added that if they really are doing this, there must be “a clear fitness benefit.”
“有各种原因会让你想要远离粪便，”鲍伊说。她补充道，如果动物真的这么做的话，一定有“一个明确的健康方面的好处”。
The researchers propose that this filthy act is all about tolerating low temperatures.
研究人员提出，这一污秽的行为完全是为了忍受低温。
Field observations revealed that wild bears seemed to smear themselves with scat on a schedule, preferentially engaging with excrement during the cooler fall and winter months.
田野观察显示，野生大熊猫似乎会定期将粪便抹在身上，在较为寒冷的秋季和冬季会倾向于接触粪便。
A chemical analysis of the dung revealed two short-lived compounds called sesquiterpenes, which are commonly found in plants. When applied onto the paws and fur of laboratory mice, the sesquiterpenes rendered the rodents indifferent to frigid temperatures or a chemically induced chill. Further lab experiments showed the sesquiterpenes were gumming up a type of cold-sensing protein that adorns the cells of pandas and many other animals, including humans.
对马粪的一项化验发现了两种名为倍半萜烯的短命化合物，它们通常存在于植物里。在抹到实验小鼠的爪子和皮毛上后，倍半萜烯便会让这种啮齿类动物感受不到寒冷气温或是一种由化学物质诱导的寒冷。进一步的实验显示，倍半萜烯会破坏某种感受寒冷的蛋白质，大熊猫和包括人在内的许多其他动物的细胞都含有这种蛋白质。
In theory, these chemicals, when applied topically like a salve, might temporarily inure pandas to the cold, Dr. Wei said.
理论上来说，当这些化合物像药膏一样外敷时，可能暂时让大熊猫习惯寒冷，魏辅文说。
Bill McShea, a wildlife ecologist at the Smithsonian Conservation Biology Institute who wasn’t involved in the study, said, “I never would’ve thought of that in a million years.”
史密森尼生物保护研究所(Smithsonian Conservation Biology Institute)的野生动植物生态专家比尔·麦克夏(Bill McShea)说，“我是绝对想不到这个的。”他没有参与该项研究。
“I would look at that behavior and say, ‘Wow, that’s weird,’” he said. “They took it to the next level.”
“我会看到这个行为然后说，‘这可真奇怪，’”他说。“而他们进行了仔细的探究。”
It’s still unclear how ubiquitous this behavior is among pandas, and whether other animals might also swaddle themselves in scat for warmth. Also mysterious is the particular allure of horse manure.
目前尚不清楚这种行为在大熊猫中有多普遍，以及其他动物是否也会为了保暖把自己包裹在粪便之中。马粪的独特魅力也是个谜。
And if the idea pans out, it would be a bit baffling, Dr. McShea said. Pandas, like other bears, have very thick coats of fur. “They are adapted for cold weather already,” he said.
如果这一理论得到证实，会让人感到困惑，麦克夏说。大熊猫和其他熊科动物一样，都有着厚厚的毛皮。“它们已经十分适应寒冷天气了，”他说。
Dr. Bowie was also hesitant to embrace the waste-as-warmth hypothesis. “How much of a benefit could this provide as opposed to finding a cave where there’s no wind?” she said.
鲍伊也没有立刻接纳这个“用粪便来保暖”的假说。“相比于找一个没有寒风的洞穴，这种行为能带来多少好处？”她说。
Isaac Chiu, a neuroscientist at Harvard University who wasn’t involved in the study, praised the team’s molecular work, but added that the sesquiterpenes the researchers found in horse manure can do far more than blunt an animal’s ability to sense the cold. Other research has found that these same chemicals might also tamp down inflammation and perception of pain.
没有参与该研究的哈佛大学神经系统学家艾萨克·赵(Isaac Chiu)赞扬了这个团队在分子研究方面的成果，但也说这些研究人员在马粪里找到的倍半萜烯的作用远不止让动物感觉不到冷。其他研究发现，它可能会抑制炎症和痛感。
Still, it’s possible that a patina of poo is just what the bears need to feel cozy.
但大熊猫也有可能只需要一层粪便来感受舒适。
“Maybe it’s like Vicks VapoRub, or maybe like Tiger Balm,” Dr. McShea said, describing the tingly feeling they cause.
“也许这就像是维克斯达姆薄荷膏(Vicks VapoRub)或者像虎牌万金油一样，”麦克夏描述其引起的刺痛感时说。
“I don’t know, though,” he added. “I’ve never rolled in horse manure.”
“但我不知道，”他说。“我从来没在马粪里打过滚。”