陈延洲

by Michael Slezak

树袋熊，又称“考拉”，是澳大利亚的国宝，性情温顺，体态憨厚，以桉树叶和嫩枝为食；一生的大部分时间都生活在桉树上，但偶尔也会因为更换栖息树木或吞食帮助消化的砾石下到地面。考拉身体新陈代谢较慢，每日需睡眠17到20小时。

Koalas spend a lot of their time sleeping， clinging to1 tree branches. But far from being lazy， it seems tree-hugging is an efficient way to keep cool.

考拉大多数时间都会抱住树枝睡觉。但也许这并不是因为它们懒惰，而是因为抱着树可以有效地使自己保持凉爽。

Koalas can usually endure2 temperatures above 40℃. They cool themselves by panting3 and licking their fur， but they do not sweat. So Natalie Briscoe from the University of Melbourne in Australia expected them to move into shadier areas when the temperature rose. But， in fact， they stay in shady areas most of the time anyway.

考拉一般可以忍受40多摄氏度的高温。它们通过喘息和舔舐自己的皮毛来降温，但是它们不会出汗。于是澳大利亚墨尔本大学的纳塔利·布里斯柯认为它们在气温升高时会躲到阴凉地儿去。不过，实际上它们大部分时间都是在阴凉地儿呆着。

“As it got hotter， they started moving down to the tree trunks and hugged really tightly4 to the trunks.” says her colleague Michael Kearney.

“当天气热起来的时候，它们会往下转移到树干，然后紧紧抱住它。”她的同事迈克尔·卡尼这样说。

So Briscoe used infrared cameras to measure5 the temperatures of the trunks and found they were much cooler than the air on hot days. At that point， “it was absolutely6 obvious what they were doing，” says Kearney.

布里斯柯用红外照相机测量了树干的温度后发现，树干的确在天热时比空气更凉爽。从这一点来看，“考拉抱树的原因显而易见了。”卡尼说道。

Briscoe tracked 37 koalas and watched their behaviour. He found that they not only moved to lower parts of the trunks in hot weather but also changed their posture， tending to hug branches when it was very warm， but sit upright7 in mild weather. In extremely hot conditions， they even spent time hugging the trunks of wattle trees， which they cant eat， but which have cooler trunks.

布里斯柯追踪了37只考拉并观察它们的行为，他发现它们不仅会在天热时挪到树干较低的位置，还会根据情况变换自己的姿势，比如在很热的时候抱住树枝，而在温和的天气里笔直地坐着。在极度高温的条件下，它们甚至会抱住金合欢树（考拉不吃金合欢树的树叶）——仅仅因为这种树的树干更凉爽。

The trees are probably cooled by the roots sucking up water from underground where the sun doesnt heat the soil so much， says Kearney.

卡尼说，树干凉爽的原因很可能是因为地下的土壤不会受到太阳的炙烤，从而使树根所吸收的地下水分可以保持清凉。……