'Ark' Designed to Save Imperiled Amphibians

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."