Seven tiny frog species found on seven mountains

Seven new species of tiny frog have been discovered on seven different mountains in south-eastern Brazil, the BBC reports. 

The cool "cloud forests" of this region have a unique climate, separated by warmer valleys that isolate the peaks like islands.

That isolation has produced 21 known species of Brachycephalus frog - and the new arrivals push that count to 28.

They are all less than 1cm long and many have colorful, poisonous skin to help them avoid becoming tiny meals.

The newly discovered species, reported in the journal PeerJ, are the fruit of five years of expeditions into the wilderness.

Marcio Pie, a professor at the Federal University of Parana in nearby Curitiba, said he had climbed more mountains than he can remember.

"It's really exhausting," he told the BBC. "The mountains are not that high - most of them are 1,000m to 1,500m - it's just that the trails are not particularly well marked."

These high forests near Brazil's southern Atlantic coast are a fertile place for ecologists to explore, Prof Pie said, yielding more different species per square km than the Amazon.

For animals like the Bracycephalus frogs that are particularly sensitive to their environment, even the temperature change from mountain to valley forms a barrier. That leaves the population on each mountain top to slowly develop into a separate species.

The little creatures are rather restricted in terms of just how different they can become. As some of the very smallest land-dwelling vertebrates, much of their anatomy is optimized to this tiny scale. For example, they typically have three toes and two fingers, instead of the five toes and four fingers found in most frogs.

The most obvious differences between Brachycephalus species, including the seven new ones, is their skin. This can vary quite a lot in how bumpy and rough it is, and quite dramatically in its color – with more vibrant tones normally reflecting higher levels of the deadly chemical tetrodotoxin.

Predicting what a new species might look like became a bit of a game for Prof Pie and his colleagues.

"It's a really exciting experience, because we have a good expectation that each mountain top will have a new species, but we don't know what it's going to look like," he said.

"So we play around while we plan each trip, and try to anticipate what the species is going to look like."