SSS 2010-07-26

（单词翻译）

You’d think an animal that hops¹ would know how to land. But for a kind of frog, that’s not the case. Imagine trying to catch a frog. You reach and they jump, only to land gracefully³ on their feet a few feet away.

It was thought that all frogs moved this way. They'd push off with their back legs, and then once in flight, rotate the limbs forward. Then they landed fore-limbs first. But researchers compared frogs of the family Leiopelmatidae, which still sport an ancient physiology⁴, to two more modern frog species. Unlike their more graceful² cousins, the primitive⁵ frogs kept their back legs straight out after they jumped. So they don’t land on their feet. Instead, they do an ungainly belly⁶ flop⁷, and then struggle to get to their feet and jump again. The finding is in the journal Naturwissenschaften.

The scientists say that the back-leg push-off must have evolved first, with the ability to rotate and land softly evolving later. Although the bad landers are still around, their more controlled relatives appear to be better at making longer trips, foraging⁸ for food and, most importantly, avoiding other animals that have an interest in frog legs—for dinner.

Thanks for the minute for Scientific American’s 60-Second Science. I’m Cynthia Graber