This frog easily fits on a ten peso coin, making it one of the smallest frogs in the world. In southern Mexico, scientists have discovered six new species of these tiny amphibians – none of which grow to more than 15 millimeters.
“Biodiversity research tends to focus on larger, charismatic animals and may neglect smaller species,” says senior author Eric Smith of the University of Texas at Arlington. “That’s why these little frogs went undiscovered for so long.” A research team led by Tom Jameson from the University of Cambridge has now devoted itself to these special amphibians.
The scientists searched the undergrowth in the southern Mexican states of Oaxaca, Mexico, Guerrero and Jalisco. “These animals live in a very limited space among fallen leaves on the mountainsides,” Smith explains. “If you walk too fast or too far, you can simply overlook them.” In their investigation, they finally found six frogs of the species Craugastor mexicanus and Craugastor pygmaeus that had not been classified in detail before.
According to the scientists, the exceptionally small body size of the discovered amphibians is related to the so-called pedomorphosis. In this evolutionary phenomenon, animals reproduce at progressively earlier stages of development over time, resulting in underdevelopment of some traits. Even when they are fully grown, Mexican frogs remain smaller than average.
In addition to the challenge of not overlooking the tiny amphibians, the scientists faced other problems in their work. In some research areas, such as Guerrero and Michoacan, they could not continue their work safely because the areas are partly controlled by armed groups that act independently of the state.
“Our sampling of western Mexico and east of the Tehuantepec Isthmus is very limited, but we already know of other new species from this group that have yet to be described,” Smith explains. With the progressive limitation of their habitat, the scientists also recommend putting the frogs directly on the list of endangered species.