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Desert Diary

Amphibians & Reptiles/Toad Metamorphosis


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Red, squalling, and—to everyone except the parents—downright ugly! Nevertheless, we all immediately recognize a baby as a miniature human. True, the proportions aren't quite right and it's going to be awhile before it talks and walks, but clearly human nonetheless.

On the other hand, take a look at some very distant relatives of ours: If we watch their water-lain eggs, we'll see them hatch into what look like little fish to the uninitiated, with a streamlined body, a tail fin, gills sticking out of its neck, and nary a sign of legs. Obviously, a baby fish that'll grow up to be a bigger fish—or is it? Watch carefully, and you'll see one of nature's marvels. Over time, stubs appear that soon transform into legs, and gills and tail retreat into the body. Lo and behold, metamorphosis—from tadpole to toad!

Some toads have the luxury of taking their time. But not our desert spadefoot toads. Breeding in short-lived pools during the rainy season, it's a deadly race between metamorphosis and a dry pool and death. pen and ink


Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.


Two tadpoles (probably common toads, genus Bufo) in the process of metamorphosis. The tail is still present in both, but the hind legs are well underway. The coiled structure in the upper tadpole is the intestine, seen through the translucent skin; the mouth is visible to the far right. Preserved specimens, photograph by A.H. Harris.



Degenhardt, W. G., C. W. Painter, and A. H. Price. 1996. Amphibians and reptiles of New Mexico. University of New Mexico Press, Albuquerque. 431 pp.

Web Resources

Overview of Couch's Spadefoot from the University of Michigan Museum of Zoology.

Photographs of adult spadefoot toads, with links to individual species.