This week 100 tiny Kihansi spray toads landed in Tanzania after a flight from the United States, where they were born and bred.

This rare amphibian species is native to Tanzania, but not just anywhere in Tanzania. The natural habitat for the penny-size toads is equally small—just 5 acres of the Kihansi Gorge, to be precise, where they once thrived in the mist zone formed by the waterfalls.

The Kihansi spray toad wasn't discovered until 1996, at which point the species was already in danger. Three years later, the creation of a new hydroelectric dam would block much of water flow to the Kihansi Gorge, drastically reducing the spray of the waterfalls. The construction project rendered the toads effectively homeless, and scientists haven't seen them in the wild since 2004.

But in a bold effort to save the species from total extinction, the WCS Bronx Zoo and The Toledo Zoo have worked in close partnership with the Tanzanian government and the World Bank to rear the toads in zoos and then release them to the wild.

Generating one-third of Tanzania’s total electrical supply, the Kihansi dam is vital to the Tanzanian economy. With funding from the World Bank, which constructed the dam, WCS and the Tanzanian government agreed to have scientists and Tanzanian officials to take an assurance colony of almost 500 Kihansi spray toads from the gorge and bring them to the U.S.

Now, some of the offspring of those toads are back in their homeland. From the airport, the toads traveled to a new, state-of the-art propagation center in Dar es Salaam, where they will stay until they return to the gorge, which is now equipped with sprinklers to artificially mist the toads.

“For years, the Bronx Zoo has been anticipating this important step toward reintroduction of the species, and we are ecstatic that the first toads are thriving in the new facility,” said Jim Breheny, the director of the Bronx Zoo.

About 5,000 toads still live at The Toledo Zoo and 1,500 reside at the Bronx Zoo. The two zoos will continue breeding and exhibiting the animals, and will send more toads to Tanzania as their numbers rebound.

“On behalf of the Government of the United Republic of Tanzania, we are very grateful to the Bronx Zoo and The Toledo Zoo for taking care of these precious toads for ten years,” said Anna Maembe on behalf of the Government of Tanzania. “They have safely arrived home via KLM flight and all 100 toads are cheerful as witnessed by our Tanzanian trained Kihansi spray toad keepers at the facility at UDSM Zoology Department. We are very optimistic that they will acclimatize soon and be taken to their homeland in Kihansi Gorge in the near future.”

Last year, the International Union for the Conservation of Nature declared the Kihansi spray toad extinct in the wild. Scientists believe that in addition to the habitat loss, pesticide exposure and the emergence of the chytrid fungus are to blame for the toads' dramatic decline. Chytrid is responsible for alarming crashes and extinctions of amphibian species in many parts of the world.

Zoo officials hope that the reintroduction of the toads and the strides made in Tanzania will help to turn the tide for the species. “We are extremely proud of the staff members, curators, and keepers whose expertise in scientific husbandry made this tremendous accomplishment possible,” said Anne Baker, The Toledo Zoo’s Executive Director and CEO. “The level of collaboration involved here, from the World Bank, the Tanzanian government, and the participating zoos to the Tanzanian field biologists and students who shared their knowledge with us, has been nothing short of inspiring.”