科學(xué)60秒:飛行的代價(jià)

More than 60 mammal species—like the famous flying squirrel—have adapted the ability to sail from tree to tree. [--1--], yes. But what’s the evolutionary advantage?

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 [--2--] their legs.

The scientists placed accelerometers onto the backs of six [--3--] 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 [--4--] than walking. Those findings appear in the Journal of Experimental Biology. [Gregory Byrnes et al, Gliding saves time but not energy in Malayan colugos (citation to come)]

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, [--5--] the air is an easy getaway from predators. In the end, it’s not too different from human flight—costs more, but way faster.
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