Scientists Still Finding New Frog Species

May 28, 2004 -- Not all frogs are as green or as friendly as Kermit.

Julian Faivovich's fingers have been chomped several times while trying to collect specimens of the very rotund ornate horned frog.

"They bite hard," said Faivovich, a graduate student in herpetology and co-curator of a live frog exhibit opening this weekend at the American Museum of Natural History in New York City. "They have two very sharp teeth protruding from the bottom jaw."

If threatened, the fire-bellied toad throws its legs into the air to flash its menacing bright orange belly. And if that isn't enough to scare off trouble, its back is coated with lethal toxic secretions.

Sharp teeth and bright orange may not be qualities that usually come to mind when most think of frogs, but that's part of the problem. Ignorance of what's out there is a real hurdle when it comes to ensuring frogs' survival.

"We're in a phase of loss," said Christopher Raxworthy, associate curator of the department of herpetology at AMNH. "Just as we're learning about new species, we may be losing them."

Big, Small, Fierce, Weird

So far, researchers have recorded the existence of some 4,900 frog species (that includes toads, which are a kind of frog that are generally browner and drier and have more warts). But Raxworthy says there are likely many more. He estimates that researchers will have identified close to 6,000 frog species by the end of his lifetime. Since 1995, alone, he points out, 990 new species have been described.

There is the squat, round African bullfrog that lives underground 11 months out of the year, emerging only to mate and eat insects, birds and rodents. On a more delicate scale, the narrow mouth toad spans only 1 ½ inches and dines on ants and snails.

The golden poison dart frog is also petite, but packs a lethal poison. The tiny yellow creature from Central and South America emits enough poison on its back to kill up to 10 people, according to Taran Grant, a herpetology graduate student and co-curator at AMNH.

The gastric brooding frog of Australia is known for the unusual way its females gulp down their own eggs and then suppress their gastric juices as the eggs develop. Weeks later little frogs emerge one by one from their mouths. The Darwin frogs of South America have a similar brooding behavior, except it is the male frog that swallows the developing tadpoles and carries them in his vocal sacs.

As researchers study such wide-ranging behaviors of the frog family, they've been racing to understand what may be killing the amphibians.

Mysterious Killer

The U.S. Geological Survey found in 2000 that up to one-third of the nation's amphibians have vanished from their local habitats. In high elevation regions of South America and Australia, entire species of frogs have been reported missing for nearly a decade.

Some have blamed the disappearances on a fungus-like organism that penetrates the frogs' skin and stifles respiration. Others have identified a virus that might be spreading through species. Still others see environmental factors, including habitat loss and increased exposure to ultraviolet radiation due to ozone thinning and chemical contaminants, as culprits.

All may be right, says Raxworthy.

"It may be a synergy of factors," he said. "But to find the smoking gun — to find those dead frogs in ponds and diagnose them — remains a challenge."

In the meantime, despite their apparent diminishing numbers, there is plenty of variety within the world of frogs left to explore and, perhaps, even to inspire.

While eyeing the hefty African bullfrog at the AMNH exhibit, New Yorker Debby Branch wondered if the animal could play a beneficial role in her hometown.

"Maybe we could use this guy," she said. "We've got rats all over this city."