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Leaping to Their Aid
As amphibians continue to decline faster than any other group of vertebrates, Smithsonian scientists and their partners work together to save them.
by Dan Stone
A few years ago, while rescuing frogs in Panama, Smithsonian National Zoo biologist Matt Evans and his colleagues were in a pinch. After removing the amphibians from the path of a deadly microscopic fungus also known as chytrid, they had no place to hold the rescued frogs while an evacuation center was built. So what did they do? What any resourceful scientist would do: put them up in a hotel.
Evans, who at the time worked for the National Aquarium in Baltimore, went to Panama as part of a rapid response team that was helping save a number of species in the path of the dangerous fungus. “We had to act quickly,” Evans says. “Chytrid was already devastating some of the area’s amphibian population, so we targeted specific species in specific localities.”
After they caught the frogs, Evans and his associates tested them for the fungus and then brought them to a hotel near the El Valle de Antón region of Panama. The hotel actually donated a few of its rooms and a holding facility for the cause. “It was an amazing sight to see all these rare frogs together in a few rooms,” says Evans. “From June to August 2005, 42 species and 624 amphibians were collected as part of this project. Most frogs were housed in individual containers prior to their trip to the United States via our carry-on luggage.”
|Panamanian golden frogs are considered extinct in the wild but can be found at the National Zoo. (Jessie Cohen/NZP)|
With each passing day, amphibians around the world continue to disappear. A recent five-year survey by the International Union for Conservation of Nature (IUCN) and Conservation International of all 5,743 known amphibian species—including frogs, toads, salamanders, and caecilians—found that 42 percent were in danger of extinction. This number is much higher than any other class of vertebrates, including birds (13 percent are threatened with extinction) and mammals (26 percent). Scientists believe that at least 122 amphibian species have gone extinct since 1980, compared to five bird species and no mammals.
“As a group, amphibians have the same evolutionary importance as mammals, and what’s happening to them could happen to mammals—including humans,” says Claude Gascon, executive vice president of programs and science at Conservation International. “That should open our eyes to our collective footprint on the planet and its effect on living things.”
What’s to blame for amphibian decline? One of the main culprits is habitat destruction. But that’s not the only problem. Climate change and pollution are also wreaking havoc on our amphibian friends.
Since the 1980s, scientists have studied enigmatic declines and inexplicable crashes in populations of mountain-dwelling amphibians in the United States, Australia, and Central and South America. Smithsonian scientist Bill Laurence first speculated in 1996 that a disease might have been responsible for these population reductions. He was right; in 1999, scientists at the Smithsonian’s National Zoo and University of Maine discovered the chytrid fungus and determined that it was the cause of a deadly amphibian disease (see “More Than Skin Deep”).
“The Zoo’s discovery of the fungus completely changed the way scientists and conservationists viewed amphibian declines,” says Brian Gratwicke, interdisciplinary research biologist at the National Zoo. “Many historic disappearances of species were then re-examined and attributed to the chytrid epidemic.”
A Crisis in Panama
Recent investigations by scientists have documented the wave-like spread of chytrid through the mountainous regions of Central and South America. One of these scientists, Karen Lips, a Smithsonian associate, has studied the fungus in Panama and parts of South America since the early 1990s. From conducting disease surveillance to testing frogs to predicting where chytrid will hit next, Lips has been on the front lines of amphibian conservation for years.
Researcher Brian Gratwicke with a cane toad.(Brian Gratwicke/NZP)
“I’ve seen chytrid’s devastating effects firsthand,” she says. “Before it enters a site, the area is abundant with life and has a high diversity of amphibian species. Then, almost instantly, there is sort of this widespread infection and within four months the abundance of amphibians and numbers of species significantly decrease.”
Even Panama’s national symbol, the Panamanian golden frog (Atelopus zeteki), has suffered at the hands of chytrid. Many scientists believe these frogs are now completely extinct in the wild because of the fungus and habitat loss.
Thus far, scientists have determined that chytrid travels about 13 miles a year in Central America. When, as predicted by Lips, chytrid arrived at El Copé in western Panama in late 2004, species from all seven frog families in the area started dying. “Within months, half of all the species vanished all together, and the abundance of many surviving species plummeted to about 20 percent of what it should be,” says Gratwicke.
Continuing its spread eastward, the fungus arrived in the El Valle region, about 22 miles west of El Copé, in late 2006.
Here, conservationists associated with the Houston Zoo began capturing and housing species in a quarantined, managed-care facility that provided protection from chytrid exposure. Today, this small center at the El Nispero Zoo in Panama houses 50 amphibian species, 17 of which are likely extinct in the wild at El Valle.
Across the Canal
Biologists had hoped that the low-lying Panama Canal region would serve as a natural barrier to the spread of chytrid. However, by late 2007, the fungus was found for the first time east of the canal in Soberania National Park. “We’re not exactly sure how it crossed the canal,” says Lips. “It may have traveled naturally or people may have tracked it over on their boots, cars, or trucks.”
Now that the fungus has jumped the canal, Lips and her colleagues expect it will continue its eastward march toward the mountainous Darien Region, the last intact amphibian hotspot in Central America. This area contains at least 121 amphibian species—61 percent of all of Panama’s amphibian fauna—and is a stronghold for about 60 species listed as critically endangered or endangered by the IUCN.
“The diversity in the Darien Region is incredible,” says Evans. “It is a biological paradise—and not just for amphibians, but for many species. It would be a tragedy if anything happened to that pristine habitat.”
|Frog habitat in Panama. (Brian Gratwicke /NZP)|
Golden Frogs at the Zoo
Throughout the United States, only eight zoos breed Panamanian golden frogs (about 50 have them on exhibit). The National Zoo, which has one of the largest holding facilities for these amphibians, has bred golden frogs in hopes of contributing to a reservoir of zoo genes that will help ensure their survival.
“Four pairs of Panamanian golden frogs came to the Zoo in 2004,” says Evans. “Over the years they have produced hundreds of offspring, some of which have gone to other zoos to participate in the Panamanian golden frog Species Survival Plan.”
At the Reptile Discovery Center, visitors can see about 12 Panamanian golden frogs on exhibit. But this number represents only a fraction of the Zoo’s entire golden frog collection; more than 80 live in an off-exhibit, temperature-controlled holding facility at the Reptile Discovery Center. All of the Zoo’s current collection descended from the original pairs.
Found in high elevations and cloudy forested areas, Panamanian golden frogs need climate-controlled environments when living in zoos. An ideal temperature for them is around 70 degrees Fahrenheit with high humidity.
The more Zoo visitors learn about Panamanian golden frogs, the more fascinating they find these charismatic amphibians. “Many people don’t know that golden frogs are actually toads,” says Evans. “They are from the genus Atelopus, but from the family Bufonidae, which are true toads. Of course, their appearance is quite different from other toads and they don’t have warty skin.”
In the wild, Panamanian golden frogs eat mites and ants that make them poisonous. Since their Zoo diet doesn’t include
these insects, the Zoo’s collection carries no threat for keepers or other animals.
A Potential Cure?
Among frog populations in zoos, the chytrid fungus can be eliminated with fungicides. But using massive amounts of this
treatment in the wild would likely cause irreparable harm to natural ecosystems, probably without stamping out all the chytrid fungus. That’s why Reid Harris, a biology professor at James Madison University in Virginia, is studying an alternative solution. He and his colleagues recently identified several species of bacteria that live on the skin of certain amphibians. But these are no ordinary bacteria—they produce anti-fungal chemicals that inhibit the growth of chytrid.
One of Harris’s most promising studies involved treating uninfected mountain yellow-legged frogs with the anti-chytrid bacterium. Of the frogs treated with the bacterium, 100 percent survived exposure to the chytrid fungus. In another study, 13 chytrid-infected frogs treated with the bacterium lost less weight when compared with untreated individuals. Weight loss is one symptom of chytrid infection.
Smithsonian research associate Louise Rollins-Smith plans to build on Harris's work. She and her team at Vanderbilt University are hoping to find a way to protect amphibians in Panama, either by vaccination against the chytrid fungus or by finding some kind of bacterium on a Panamanian amphibian that is similar to what Harris found on the skin of mountain yellow-legged frogs. “Our research is helping us understand the immune response of Panamanian amphibians,” Rollins-Smith says. “We hope to use that information to help save them.”
Rollins-Smith and her colleagues believe frogs’ skin holds benefits for humans, too. They are researching whether certain antiviral peptides in amphibians’ skin may prevent the transmission of the HIV/AIDS virus. “If we lose amphibians, we lose the opportunity to study the medicines that might be found in their skin,” she says. “We must do all we can to ensure their survival.”
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