Extinct Toad on Exhibit at WCS’s Bronx Zoo

February 2, 2010

The new exhibit highlights the work of WCS to conserve the Kihansi spray toad, which has disappeared from its native home in the Kihansi Gorge of Tanzania.

The Kihansi spray toad, which has hopped into oblivion in its native home of Tanzania, has found a safe haven at the Wildlife Conservation Society’s Bronx Zoo. A new exhibit at the zoo’s World of Reptiles features an “assurance colony” of the small, mustard-colored toads, a species listed as extinct in the wild last year by the International Union for Conservation of Nature (IUCN).

The chirps of Kihansi spray toads once filled a verdant, five-acre swath of Tanzania’s Kihansi Gorge, where the toads lived in the mist created by the waterfalls in the gorge. The species, unusual in that females give birth to fully-formed young, rather than laying eggs that hatch into tadpoles, is also exceedingly rare—it lives nowhere else in the world.

For the first time at the Bronx Zoo, visitors will be able to see and learn about the Kihansi spray toad. The exhibit is as unique as its inhabitants. To keep the toads comfortable, the zoo built a specialized filtration system that cools the water and treats it with ozone. A series of nozzles delivers the water to the animals in a fine mist that mimics their native clime.

The exhibit is a window into the conservation efforts of a team of herpetologists at WCS’s Bronx Zoo. For the past nine years, they have worked behind the scenes to ensure the toad does not disappear altogether from the planet, by propagating the species for eventual reintroduction into its natural habitat.

What happened to the Kihansi spray toad?


In 2000, the construction of a hydroelectric dam in the Kihansi Gorge was predicted to dramatically change the spray toad’s microhabitat in the falls. The dam provided much-needed power to Tanzania, generating a third of the country’s total electrical supply. But its construction reduced the original size of the Kihansi falls to 10 percent of its former flow, drastically curtailing the mist zone in which the toads thrived.

Following an agreement between WCS and the government of Tanzania, WCS scientists and Tanzanian officials collected 499 Kihansi spray toads from the gorge. The small colony was brought back to New York to initiate the off-site conservation program.

Scientists are still debating the ultimate cause of extinction of this species in the wild, but it likely resulted from a combination of habitat change and the emergence of infective chytrid fungus, which is responsible for wiping out an alarming number of amphibian species in many parts of the world. The Bronx Zoo and the Toledo Zoo in Ohio shelter the only remaining populations of Kihansi spray toads, which collectively number more than 4,000 individuals.

The project is now entering the repatriation stage, in which WCS is working with the government of Tanzania and several international partners to return a small population to a facility at the University of Dar es Salaam within the next year. The Tanzanian government has also been managing the Lower Kihansi Environment Management Project in the gorge. In preparation for the species’ return, Tanzanian park rangers have installed a system of sprinklers, replicating the toad’s habitat. When habitat conditions can be assured for the toads’ long-term survival, WCS and its partners hope to return the species to the wild.
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