Where Have All the Frogs Gone?

By Colleen M. Smith

As part of our ongoing efforts to educate people about the rainforest and its inhabitants, KSTR is tracking the decline of indigenous frog populations within and outside of Costa Rica.

For the past three decades, scientists in Central and North America have been closely following a wave of disease that has wiped out amphibians in the Central American highlands. The fungal disease, called chytridiomycosis, has been advancing at a rate of about 30 kilometers per year and eradicating dozens of frog species in its path. Scientists have identified this as the same disease that killed off Costa Rica’s golden frogs in the 1980s.

Anticipating the spread of the disease outside of Costa Rica, researchers from the Smithsonian Tropical Research Institute in Panama and the University of Maryland in the U.S. set up a monitoring program in El Copé, Panama to track the effects of the devastation.  The area’s abundant amphibian community allowed Karen Lips, associate professor of biology at the University of Maryland, and a team of scientists to study frog populations before, during, and after the arrival of the disease.

In the seven years of field studies and data collection prior to the disease outbreak in 2004, Lips and her group were able to identify 63 different species of frogs located in El Copé’s Omar Torrijos National Park. 25 of those species disappeared from the site in the subsequent epidemic that spanned from 2004 to 2008, with no species reappearing there as of 2008.

Given the magnitude of the amphibian population in that specific region, the scientists questioned if there were undiscovered species of frogs that vanished even before they could be known to the world. Using a genetic technique called DNA barcoding, the team was able to study the DNA sequences that make each living organism, or in this case frog, unique. The data showed 11 additional species of frogs that had yet to be discovered before the epidemic hit, and of these 11 species, 5 had been wiped out by the deadly disease.

“It’s sadly ironic that we are discovering new species nearly as fast as we are losing them,” said Andrew Crawford, former postdoctoral fellow at Smithsonian Tropical Research Institute and member of the Círculo Herpetológico de Panamá. “Our DNA barcode data reveal new species even at this relatively well-studied site, yet the field sampling shows that many of these species new to science are already gone here.”

The study—the first before and after view of amphibian die-off—raises the question of just how many undiscovered frog species have already been lost due to the disease epidemic. The results were published online in Proceedings of the National Academy of Science.

KSTR will continue to follow the effects of the epidemic and investigate ways in which we can help save the frogs in our area.