Meet the shape-shifting baby amphibians that become cannibals

Some young salamanders and frogs are able to grow bigger heads and "fangs," which enable them to eat their kin and grow faster.

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An adult long-toed salamander (Ambystoma macrodactylum) photographed in Deschutes County, Oregon. In its larval stage, this species may grow a bigger head and vomerine teeth if food in its pond is scarce.

High in the Three Sisters mountains of the Cascade Range in central Oregon, researchers had to hike—and then ski—to get to the quiet ephemeral pool. Strange-looking salamanders, and not much else, lived in the water.

“I noticed right away that the [salamander] larvae were really skinny and big-headed,” says Susan Walls, now a research biologist with the United States Geological Survey. When she looked closer, she could see that the heads and jaws of this population of long-toed salamanders were much bigger than normal. It turns out that these larger mouths served a very specific purpose: cannibalism.

In one of the first research papers on this subject featuring salamanders, Walls had described how these larger jaws also held bigger vomerine teeth (which, in this species, are usually just small bumps behind the front row of teeth) that had grown resemble fangs. All the better to eat their brethren with—but why?

As juveniles, before they graduate to living on land, long-toed salamanders can “shape-shift”—their heads and jaws get bigger in proportion to their bodies, and their vomerine teeth become more pronounced....

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