A Tanzanian dam cut a waterfall’s flow by 90%; Engineers built sprinklers to save the coin-sized toad that lived there

The Kihansi Spray Toad, which lived on roughly five acres of wet rock and moss in a gorge in Tanzania’s Udzungwa Mountains. It was found nowhere else on Earth. According to the Global Environment Facility (GEF), one toad could sit on a dime with room to spare, and its young, born fully formed rather than hatched from eggs, could fit on the head of a pin.

What kept the species going was mist. Spray thrown up by the Kihansi waterfall kept that small patch of the gorge soaked through the year. Take the spray away and the toads had nothing else.

The dam took 90% of the waterfall

Scientists first described the toad in 1999, the year before the Kihansi dam began operating, Scientific American’s Extinction Countdown blog reported in 2012. The plant supplied nearly a quarter of Tanzania’s electricity at the time, the report noted. It also cut the water reaching the gorge’s falls by 90 per cent.


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Conservationists tried to protect the species in two ways. In the gorge, a gravity-fed sprinkler system was installed to imitate the lost spray using what little water remained, GEF says in its account of the project, which the World Bank implemented. Away from it, the Bronx Zoo collected 499 toads in 2000, at the Tanzanian government’s invitation, to hold as an insurance population.

The state utility, TANESCO, monitors the water that reaches the gorge, and the Tanzanian government committed to maintaining the misting system, Scientific American reported.

From 20,000 to zero

GEF puts the wild population at around 20,000 before it collapsed although accounts differ on the timing. A 2024 paper reports toads being collected dead in the gorge between June and August 2003, during what it calls the species’ terminal decline. GEF’s feature story, however, dates the crash to 2005. By 2009, the toad had been declared extinct in the wild.

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The cause was argued over for two decades. The sprinklers failed in 2003, Amphibian Ark notes, around the time chytridiomycosis, a deadly fungal disease, appeared. A paper in Proceedings of the Royal Society B in July 2024 went further. Researchers including Matthew Fisher sequenced DNA of the fungus from preserved toads that had died in the gorge.

It was not BdGPL, the globally notorious lineage, but one called BdCAPE, which Explorersweb’s summary describes as previously considered relatively harmless. The authors concluded that the habitat repairs had bought time, but that BdCAPE caused the final die-off. Fisher told Science, as relayed by Explorersweb, that the lineage’s aggressiveness had been underestimated.

A summary from North-West University, home to a co-author, adds that the dam-driven habitat change had already made the toads more vulnerable. The two causes, in other words, were not rivals. The dam had altered the habitat; the fungus delivered the final blow.

Seventy-two toads and a learning curve

Back in New York and Toledo, nobody knew how to keep the species. No facility had done it before, Bronx Zoo herpetology curator Don Boyer said in 2012, so staff worked it out themselves. At one point captive numbers fell to 72, GEF says, with parasites a major difficulty.

In October 2012, around 2,000 toads were reintroduced into the gorge, with contributions from the Bronx Zoo and Toledo Zoo, according to Scientific American. Additional toads had also been bred in Tanzania.

Representatives of the World Bank, the IUCN and local Tanzanian villagers attended. Conservation biologist William Newmark called releasing an amphibian where the fungus is endemic a pioneering achievement, and told GEF that the number of animals released is the best predictor of success.

Boots, pipes and a bit of grant money

A study published in Ecology and Evolution on January 9, 2026, reported that 98% of the 1,000 captive-bred toads released in February 2022 had died. The researchers identified Bd-CAPE as the cause of the mass mortality.

GEF’s 2015 feature notes the concrete footbaths at the entrance to each spray wetland to disinfect workers’ and visitors’ boots and an upstream pest-management program to reduce pesticide use. The third phase of the project ran from 2014 to 2018 and cost $5.95 million.

The Kihansi Spray Toad still remains as Extinct in the Wild. In July 2026, the Mohamed bin Zayed Species Conservation Fund gave the Tanzania Wildlife Research Institute $24,950 for disease monitoring and habitat work. The fund’s description also mentions Lufulutonya, a nearby wetland now seen as a promising second refuge.

The toad’s story shows how difficult conservation becomes when a species depends on a habitat altered by a major infrastructure project. The dam continues to provide electricity, but restoring the toad’s original environment has required artificial mist, captive breeding and continued disease monitoring.

A species that once numbered about 20,000 on five acres was held together, at its lowest, by 72 animals in zoo enclosures, and the IUCN still lists it as extinct in the wild. The dam delivered its power but the toad is still waiting to live without help.

The dam continues to generate electricity, but recreating the toad’s original habitat has required artificial mist, captive breeding and repeated attempts to return it to the wild. The discovery of Bd-CAPE has made the task harder: even when the habitat is restored, the disease still remains. For now, the Kihansi spray toad’s return depends on whether conservationists can find a way for it to survive in a place that no longer works as it once did.