The Tanzanian spray toad is a rare amphibian that has been living almost entirely in captivity for the past decade. The New York Times recently reported that the animal now has nowhere to live in the wild. Less than three quarters of an inch long, the toad used to flourish in a waterfall off the Tanzania's Kihansi River. But the river was in dammed in 2000, reducing the river to 10 percent of its former flow and virtually destroying the toad’s natural habitat.

This is bad news for the remaining 4,000 toads, all of whom of live in the Bronx Zoo and the Wildlife Conversation Society in Toledo, Ohio. The spray toad, known as Nectophrynoides asperginis, only exists today because scientists rescued them from Tanzania when the dam first opened. The toads have been preserved in the United States while living in misty tanks. 

Discovered in 1998, as many as 20,000 of the species lived in the misty waterfall tract on the Kihansi. When the dam went into operation in 2000, the moisture-dependent plants disappeared, taking most of the toads with them. The tiny amphibians were also attacked by pandemic of chytrid fungus, which has wiped out at least 120 species worldwide.   

And so, scientists sprung into action, collecting 499 spray toads into coolers for a plane ride back to the Bronx Zoo. Jim Breheny, the director of the Bronx Zoo, puts it bluntly, “It was get on the plane, collect them, get back.” Through trial and error, caretakers managed to keep the toads alive at the Bronx and Toledo zoos.

But the entire effort has called into question the logistics of preserving a species that has no place left to live. It is estimated that millions of dollars have been spent to save the tiny toads, and even more research has gone into attempts to develop a safe environment for them in the wild. As Breheny points out to the NY Times, “given the small number of spray toads, their minuscule range and their extreme vulnerability to environmental disturbance,” it may one day be determined that returning them to the wild will be impossible. And then, the entire effort would have to be re-evaluated.

One would expect the preservationists to argue that the dam should have never been built. But scientists are quick to point out that Tanzania is a poor country that needs an electricity source. And so, the issue remains a complex one.

The NY Times reports that, this month, the Bronx Zoo will display the tiny toads in a small exhibit in its Reptile House.

For further reading: Saving tiny toads without a home