Researchers say they've discovered the world's first shape-shifting amphibian, a tiny frog in Ecuador that can alter the texture of its skin from smooth to spiny in just minutes.

The changeable species dubbed "the mutable rain frog," the first vertebrate known to posses such a talent, was discovered in its native Ecuadorean forest in 2006.

However, its ability to morph its skin texture went unobserved for three years, the researchers report in The Zoological Journal of the Linnean Society.

"We took a specimen back to the house in a cup to photograph it, and when we looked in the morning, we thought we had grabbed the wrong frog," says biologist Katherine Krynak from Case Western Reserve University in Cleveland, an author of the study. "We put the frog back in the cup with some moss, and soon, it had the spines again."

The moss, plentiful in the frogs' protected cloud forest habitat, seems to be the key, the researchers say; when the creature is in moss, its skin grows bumpy with tiny tubercles, or spikes, and when it is away from any moss the skin reverts to being smooth.

For the frog, Pristimantis mutabilis, it is most likely a camouflage adaptation to protect it from birds and other predators, researchers say, although that is as yet unproven.

"The spines and coloration help them blend into mossy habitats, making it hard for us to see them," Krynak says. "But whether the texture really helps them elude predators still needs to be tested."

P. mutabilis, tiny at less than an inch long, is not alone in its unusual talent, it turns out; a related species has recently been discovered that can pull off the same shape-changing trick.

The fact that at least two species of frogs can significantly change their appearance could have broad implications for how species are identified, the scientists say, suggesting longer observations and photographs should be considered to ensure that one shape-changing species isn't inadvertently identified as two separate ones.

During almost three years of study, the scientists found that the frogs were capable of shifting their skin from spiky and bumpy to completely smooth, or vice versa, in about 3 minutes.

Previously, such skin-changing abilities have only been seen in invertebrate species such as octopus and cuttlefish.

The frog's fog-shrouded habitat, known as the Chocó cloud forest, is a protected biodiversity hotspot home to a number of rare species including birds and butterflies -- and one very talented amphibian.

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