Smart from the start
Animal embryos get some respect for their survival skills
By Susan Milius
Karen Warkentin speaks admiringly of the eggs of red-eyed tree frogs because, for one thing, they know what’s shaking.
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Masses of these glistening eggs hang on leaves that dangle over tropical ponds, and the eggs stay put even when branches thrash in storms. A hungry snake biting into one end of an egg mass can make the embryos’ home dip and dance too. But at this jouncing, older embryos flee. They can’t run, but they can hatch. A sudden burst of emergency hatching sends a rain of new tadpoles into the water, often saving some 80 percent of a clutch.