By Juliet Eilperin
Washington Post Staff Writer
Monday, May 12, 2008
NEW YORK -- The 300 Kihansi spray toads residing in a small room at the Bronx Zoo chirp cheerily as they bask in a light sprinkling of water 14 times a day. Until a few years ago, the tiny, mustard-colored toads existed only in a river gorge in Tanzania. Now the survivors are confined to the Bronx and Toledo zoos, having gone extinct in the wild.
With thousands of amphibian species facing unprecedented threats to their survival, scientists have launched a global effort to collect them in zoos in an attempt to save them from disappearing altogether. The program, called Amphibian Ark, aims to keep 500 species in captivity and breed enough to eventually reintroduce them into the wild.
"In terms of scope, I think this is the biggest conservation project that humanity has ever tried to tackle," said Kevin Zippel, the program's director, who said the initiative is testing zoos' ability to raise and maintain animals with specialized needs. "In the course of the last four years, we've realized how badly off amphibians are," he said.
Scientists have been tracking the rapid disappearance of amphibians for two decades, but new evidence suggests the animals face increasingly grave peril. A third to a half of all amphibians are now threatened with extinction; 165 species have already vanished. In Latin America and the Caribbean alone, three of every four amphibian species are critically endangered.
Research published Wednesday in PLOS One, a journal of the Public Library of Science, estimated that in the neotropic region, which spans from the Mexican deserts to Patagonia in southern Argentina, 35 percent of amphibians "are threatened by habitat loss, habitat fragmentation, and habitat split."
In response, members of the Association of Zoos and Aquariums, along with other institutions worldwide, have declared 2008 the "Year of the Frog" in an initiative to raise awareness of amphibians' plight and the roughly $440 million needed to conduct research, maintain captive species and preserve critical habitat worldwide.
"I don't think we're going to save everything we bring into captivity," said R. Andrew Odum, the Toledo Zoo's curator of herpetology, but "it's important that we try."
To give them the best chance of success, scientists are distributing amphibians to zoos around across the globe to create "assurance populations" that could potentially repopulate the wild.
Among them are 120 Panamanian golden frogs being kept at the District's National Zoo, among the 2,000 of the species now in 50 U.S. zoos.
"If you put all your eggs in one basket, you really have one basket," said Brian Gratwicke, an amphibian conservation biologist at the National Zoo, explaining why species are being kept at multiple zoos.
There are a number of reasons that frogs, toads, salamanders and wormlike caecilians are in peril.
Climate change is altering many habitats, forcing some species to move to ever-higher elevations to survive. Increased traffic poses a problem when the creatures migrate across roadways. A recent survey of Indiana highways, reported in the journal Herpetological Conservation and Biology, found that amphibians and reptiles accounted for 95 percent of roadkill. In Appalachia, mountaintop-removal mining threatens several species of salamanders, which can take 70 years to recover from such drastic disruptions.
Perhaps more important, however, may be the chytrid fungus, Batrachochytrium dendrobatidis, which researchers say has caused amphibian populations to plummet in North and South America, Europe, Africa, and Australia.
Researchers at the National Zoo first described the fungus in 1999. It attacks keratin proteins in the skin, and because amphibians breathe through their skin, this creates respiratory problems. While scientists are still debating the connection between chytrid fungus and global warming -- some believe they are inextricably linked, while others dispute this -- experts agree that the disease helps explain why amphibians are in such dire condition.
The Bronx Zoo's Kihansi spray toads fell prey to several pressures, including habitat destruction and, most likely, the fungus and pesticides. Their natural habitat encompasses just 10 acres in the Kihansi River gorge. In 2000, a World Bank-funded dam diverted 90 percent of the flow that sustained the toads, and their numbers started dropping precipitously.
By late 2000, the Wildlife Conservation Society brought 500 of the toads to U.S. zoos. A sprinkler system installed by the Tanzanian government seemed to be reviving them, but in July 2003 the population collapsed. The crash coincided with a flushing of sediment from the dam, and researchers suspect this could have unleashed pesticides from farmland runoff. Itinerant workers may also have unwittingly introduced the chytrid fungus to the area.
Last month, two herpetologists from Tanzania's University of Dar es Salaam, Charles Msuya and Wilirk Ngalason, visited the Bronx and Toledo zoos to learn how to breed the toads in captivity.
Jennifer Pramuk, the Bronx's Zoo's curator of herpetology, has spent the past year and a half exploring what works best for the tiny creatures, which at full maturity measure just three-quarters of an inch to an inch long.
"A lot of it is detective work," Pramuk said, noting that she and her staff have adjusted the phosphate levels in the frogs' water to better suit their needs. "When you have an animal that's never been kept before, there are a lot of things people didn't know."
Msuya and Ngalason are hoping to bring some of the frogs back to Tanzania within a year to breed them there before reintroducing them to the wild, but they still face the prospect of a habitat contaminated by the deadly fungus.
"So far it's a really challenging issue," Msuya said. "Nobody knows what can be done."