nature

What's happening to
the amphibians
by Eric Jackson

Back in the 1970s, scientists studying amphibians in this region and elsewhere began to notice declines in the populations of frogs and other animals they were studying. By the 1980s they were sounding the alarm. In 2004 a worldwide wildlife survey was taken and it was determined that some 43 percent of all amphibian species were in decline --- that compares to 12 percent of bird and 23 percent of mammal species. It is estimated that 168 amphibian species have gone extinct, including 122 extinctions since 1980. With lightning speed, we have seen it here in Panama, where the symbol of El Valle and its tourism, the Panamanian golden frog, has gone extinct in the wild, surviving only in few zoo and laboratory environments.

"This is something a little different," Zimbabwean biologist Brian Gratwicke told an audience swelled by the annual influx of summer students at a July 22 lecture at the Smithsonian Tropical Research Institute's Tupper Auditorium. "This is something we haven't seen before."

Dr. Gratwicke, who was a Rhodes Scholar and now works with the Smithsonian's National Zoo program to save threatened species, told the audience that "Panama is one of the most important areas on the planet today, in terms of amphibian conservation."

He told the crowd that scientists need to pay more attention to communicating with non-scientists, so as to more effectively explain why amphibians matter: "As scientists we aren't very good about talking about our value systems." He also noted a tendency among people doing basic research to narrow their concerns: "When we are in science and focusing on collecting data, we don't think so much about our tool chest of things we can do to mitigate.

And why would anyone care about frogs?

Gratwicke talked of frogs as important symbols in many cultures, from oriental bearers of prosperity to the critters that foxy occidental princesses kiss to find Prince Charming. There are frogs that secrete substances with such diverse medicinal properties as are useful for gluing injured human cartilage, retarding the growth of retroviral infections like AIDS and treating antibiotic-resistant infections. But the frog whose secretions promised to yield better treatments for peptic ulcers? "That frog went extinct," Gratwicke noted. "We don't have that option anymore."

And yes, people eat frog legs. And yes, frogs eat a lot of bugs that people don't like. And yes, the town of Rayne, Louisiana draws lots of tourists for its annual frog festival. Until very recently El Valle used to bring in tourists to see the golden frogs, too.

We know what killed off El Valle's frogs in the wild. It's the chytrid fungus, which has been spreading down the Meso-American isthmus at about 30 kilometers per year, just crossed the Panama Canal in 2007 and is headed toward the Darien. It's laying waste to upland frog populations.

Gratwicke said that chytrid is likely an invasive species issue, possibly from frogs that were used in the 1940s and 1950s in pregnancy testing. The chytrid fungus genome has been mapped and genetic tests have been done on samples of the fungus around the world and they all seem to be of the same stock, which "probably means that it is one pathogen that has spread."

But setting aside the chytrid issue for a moment, on a worldwide basis the decline of frogs and other amphibians is for usual reasons. Most of the problem is about habitat destruction, be it for urban sprawl, conversion of forests into farm, strip mines, hydroelectric dams or roads upon which frogs always come out the losers in their encounters with cars.

Climate change is an issue in amphibian decline, and changes in amphibian populations have been among the first indicators of climate change. In a number of English country estates, Gratwicke noted, people are in the habit of keeping natural diaries, one typical entry in which is the date on which the year's first frog call has been heard. Some of these records go back to the 18th century. And it turns out that the frogs are tending to be heard earlier in recent years.

In Madagascar systematic studies have shown how montane frog species are steadily moving uphill and tendencies like this have been noticed elsewhere as well. The concern is about isolated species "being pushed off the last mountain top" as the world heats up.

Pollution is also a big factor in worldwide frog decline. The herbicide Atrazine is a particularly deadly threat, and hormones that people take as medicines or eat in the meat and poultry they consume tend to break down in neither the human body nor urban sewage treatment systems, and thus tend to affect frogs.

So what can be done to protect threatened frogs? In some cases, nothing very effective. There are a number of species that now live only in carefully controlled zoo or laboratory environments, and it may or may not be possible to reintroduce them into the wild. In many cases, Gratwicke thinks it's better to concentrate on saving habitats and letting their endangered amphibians survive or perish in the wild than to catch the remaining animals and keep them in a modern ark in hopes of a later opportunity to reintroduce them somewhere. Part of the reason is that climate change is altering habitats in ways that we can't predict very well, so that conditions that might be ideal in a particular spot might be ephemeral. 

But meanwhile, there are governments, like that of the Australian state of Victoria, setting up protected areas for the benefit of frog species. Amphibians, Gratwicke pointed out, tend to have small ranges, so often can be saved in rather small protected habitats.

In the United States, an unofficial Partnership for Amphibian and Reptile Conservation advises private land owners of things they can do to protect frogs and other living things, for example, fencing off just a part of a pond where cattle drink.

On the governmental level, the US Environmental Protection Agency is now testing herbicides for their effects on amphibians, a move that may keep the Atrazine disaster from repeating itself.

In Costa Rica, a landowner who might otherwise cut down his wooded lot to grow crops on it generates income by charging a small fee to be taken on poison dart frog tours.

In India, there was the decision to cut off a lucrative business in exporting bullfrog legs by the millions of tons in order to save the amphibians as a valued wildlife resource.

"Education and awareness is an awfully important part of amphibian conservation," Gratwicke said, noting efforts ranging from reaching out to schoolteachers to Kermit the Frog's appearance before a US congressional committee. This year has been designated The Year of the Frog, and a lot of publicity, from classroom presentations to posters warning of the insect infestations we'd have if there were no frogs

And what about chytrid fungus, and our golden frogs? There are certain hopes for them.

One thing that scientists have found is that while chytrid fungus exists among lowland frogs, it doesn't seem to be so virulent among them, and that if one cares to save the life of a chytrid infected frog one must turn up the temperature of that animal's habitat to help it fight off the disease. That's what was done at the National Zoo in Washington DC when they had a chytrid epidemic in their amphibian collection.

And then there is this bacterium that was isolated from the slime on salamander skins, which has been found to have anti-fungal properties. In a California experiment it was found that frogs inoculated with these bacteria resisted chytrids.

So can we just infect a bunch of the captive golden frogs with these bacteria and turn them loose in likely habitats in and around El Valle? We don't yet know with enough certainty whether that would be a wise thing to do with some of the precious few remaining captive golden frogs. It will take more experimentation and research to make a more informed decision about that.

And should a scientist --- or anybody else --- who is visiting the Darien from a chytrid-affected part of Panama take special precautions to avoid bringing in the fungus on his or her shoes or clothing? We don't know the answer to that question either, or for that matter the roles that frogs that can be infected with chytrid without apparent ill effects might be playing as vectors in the infection's spread to other species.

So what's holding us back from figuring out a solution to this problem and getting down to the task of restoring Panama's wild golden frog population, and other threatened amphibian populations around the world? "The money just hasn't been forthcoming," Gratwicke lamented.

That's why it becomes important for scientists to be able to communicate to the general public the nature and severity of the frog decline problem, and to effectively develop and promote such solutions as can be had, rather than to limit their activities to taking notes on an amphibian holocaust.