In the tropical forests of Papua New Guinea, scientists have found a truly tiny frog. The adult frogs are just three-tenths of an inch long, which makes them a millimeter or so smaller than an itty-bitty fish found before on the Indonesian island of Sumatra.
The frogs can sit on a dime and still have space available to invite a few friends along. The little frogs are now the world’s smallest vertebrate, or animal with a backbone. An article reporting the finding was published last week in the online science journal PLoS One.
Finding The Tiny Frog
Louisiana State University herpetologist Christopher Austin and graduate student Eric Rittmeyer discovered the miniature frog in 2009, during a trip to Papua New Guinea to study the wide variety of life on the island. Herpetologists study amphibians, which includes frogs, toads, salamanders and newts.
Finding the world’s smallest frog happened by accident. The researchers were recording the calls of frogs at night near the Amau River in eastern Papua New Guinea, when they heard a bunch of high-pitched sounds. "This frog has a call that doesn't sound like a frog at all. It sounds like an insect," said Austin.
The calls were coming from all around them, and it took the two researchers a while to figure out that the sounds were coming from the ground. They thought they would find an insect. What they got instead surprised them.
"We found it by grabbing a whole handful of leaf litter and putting it into a clear plastic bag and very, very slowly going through that litter leaf by leaf by leaf until we saw that small frog hop off one of those leaves," said Austin.
Taking pictures of the frog also proved difficult. The frogs can leap 30 times their own length, and at first they weren’t posing for a photo. After hopping around for some time, though, the frogs stopped long enough for Austin to get the shot. Even so, he had to enlarge the photos in order to describe the new species.
The scientists also found another new little frog species in New Guinea. Austin estimated that they found 20 previously unknown species on the island of New Guinea. (Half the island forms part of Indonesia; the other half is the independent country Papua New Guinea.)
Claims about the tiniest animal with a spine are still up for debate. Theodore Pietsch is an ichthyologist (ick-thee-ahl-eh-jist)—a scientist who studies fish—at the University of Washington. In 2006, he described a species of deep-sea anglerfish that are about 2 mm smaller than the frogs. But only the males are that small. They don’t have stomachs, and they live as parasites on larger 1.8-inch-long female fish. Austin knew about the anglerfish, but felt that average species size—which would include both the females and males of the species—would make a better comparison.
Either way, both scientists would probably agree that finding the smallest spine isn’t the most important discovery. Instead it is understanding that lots of tiny frogs, at least 29 species worldwide, live in a unique habitat and eat creatures even tinier than they are.
"We realized these frogs were probably doing something incredibly different from what normal frogs do — invading this open niche of wet leaf litter that is full of really tiny insects that other frogs and possibly other creatures weren't eating," said Austin. And that’s how a tiny frog can be a big discovery.