Running Toads of Spain

Last semester, I had the opportunity to study abroad in Spain. This was a great experience in many ways, and as I was enrolled in a class on the natural history of Spain, I was able to become very familiar with the herps of the Iberian peninsula. There are surprisingly few amphibians there, mostly because of the arid climate, but on one field trip I was able to identify the toad Epidalea calamita (formerly Bufo calamita).

Photo: Wikipedia commons

This particular specimen (which I do not have a picture of, unfortunately) was about 2 inches long and was found hiding under a rotting log on the shore of a new reservoir. We were not able to determine the sex. This toad is commonly called the Natterjack toad in English and "el sapo corredor" in Spanish. The Spanish name translates literally to "the runner toad", which gives away the toad's most unique feature: because of its proportionally short legs, it has a running gait instead of hopping like a typical frog. After a few seconds of prompting, our specimen ran further under the log and away from us.

Natterjack toads usually prefer sandy, moist environments and are found all over western Europe, including the British Isles. They breed over a 3-month period from April to July and reproduce by spawning in small, shallow pools. Because of the arid climate in southern Europe, they tend to lose lots of tadpoles when the pools dry out. They are nocturnal and feed mostly on small insects, worms, and other small reptiles or amphibians. They are very efficient at traveling large distances despite their tiny limbs, making them good at finding mates and invading new areas.

The Natterjack toad was one of the only amphibians we found in Spain in our natural history class. I was very excited when we found it, and the running gait is a unique trait that I found very interesting. I do not recommend traveling to Spain just to see the toad, but if you happen to be there, flipping over a log in a wet, sandy area can't hurt.