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More than 60 mammal species—like the famous flying squirrel—have adapted the ability to sail from tree to tree. Thrilling, yes. But what’s the evolutionary advantage?
超过60种哺乳动物——比如著名的会飞的松鼠——拥有从一棵树跳到另一棵树的能力。有些惊讶？事实确实如此。但这种能力有什么进化意义上的优势吗？
One theory suggests gliding saves energy. So researchers tested that idea using colugos—mammals from Southeast Asia that turn into giant skin sails when they stretch out their legs.
有一种理论认为滑行节省体力。因此研究人员用飞鼯猴——一种来自东南亚的哺乳动物，当它们滑行时会伸展出四肢，变成一张巨大的翼膜。
The scientists placed accelerometers onto the backs of six compliant colugos. The data packs revealed that each colugo glided an average of a quarter-mile each night. But gliding isn’t as effortless as it looks. The researchers’ calculations suggest that flying actually requires one and a half times the energy of a conventional traverse. That’s because colugos prepare for a launch by climbing higher up the tree. And climbing’s a lot more strenuous than walking. Those findings appear in the Journal of Experimental Biology.
科学家在六只飞鼯猴背上安装了加速度计。数据报显示每只飞鼯猴平均一个夜里要滑翔1/4英里。但滑翔并不像看上去的那样省力。研究人员的计算结果显示飞行事实上要比普通的行走多用一半的力气。这是因为飞鼯猴在准备滑行之前要爬上高高的树，并且爬行比行走更耗体力。这些研究结果发表在《实验生物学杂志》上。
So why do it? The upside is speed. Colugos can sail 10 times faster than they can tightrope through the canopy. Which leaves more time to snack. Plus, leaping into the air is an easy getaway from predators. In the end, it’s not too different from human flight—costs more, but way faster.
既然这样，那么它们为什么要这么做？因为滑行比在树丛中飞檐走壁要快上10倍，这也让它们有更多的时间睡觉。此外，滑行有助于它们逃脱天敌的追捕。到头来，这跟人类的飞行一样——花费更多，但更加省时。
