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The Chosen Path

In the shallow ponds of Arizona, juvenile tiger salamanders come in two types  both with feathery gills.  Scientists discovered the tiger salamander has a unique way to survive drought.  Some eggs carry the genetic blueprints to become harmless plankton feeders.  Others become cannibals.  A month after hatching, they transform into killers -with big teeth and big heads.  Which blueprint they follow depends on the weather.  If their pond remains full  the harmless small heads dominate, feeding on plankton.  But if the summer rains fail, a shrinking pond means more big heads armed with curved teeth and strong jaws, the big heads feast on the defenseless plankton eaters.

In the shallow ponds of Arizona, juvenile tiger salamanders come in two types both with feathery gills. Scientists discovered the tiger salamander has a unique way to survive drought. Some eggs carry the genetic blueprints to become harmless plankton feeders. Others become cannibals. A month after hatching, they transform into killers -with big teeth and big heads. Which blueprint they follow depends on the weather. If their pond remains full the harmless small heads dominate, feeding on plankton. But if the summer rains fail, a shrinking pond means more big heads armed with curved teeth and strong jaws, the big heads feast on the defenseless plankton eaters.

Photograph by Getty Images

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