Reclaiming the lost world: Kihansi spray toad re-introduction in Tanzania

Summary

The Kihansi spray toad (Nectophrynoides asperginis), discovered only in 1996 in Tanzania's Kihansi river gorge, went extinct in the wild after hydropower diversion cut natural river flow from 16 to under 2 cubic meters per second, desiccating its misted-wetland habitat; the population crashed from over 20,000 to fewer than ten by late 2003, with chytridiomycosis, pesticide runoff and dam-flushing pollution suspected as compounding causes. About 500 toads had already been collected for a captive breeding program launched in December 2000 by the Tanzanian government and Wildlife Conservation Society at Bronx and Toledo Zoos in the US; early breeding suffered severe die-offs that reduced the global population to just 37 individuals, but improved husbandry has since rebuilt it to roughly 4,000. In parallel, Tanzania's Lower Kihansi Environmental Management Project restored artificial misting systems at the gorge's wetland meadows, secured a legally mandated minimum bypass flow of 2 cubic meters per second, built boardwalks to reduce trampling, and funded income-generating projects in 21 surrounding villages to reduce pesticide use and habitat encroachment. As of the report, no toads had yet been reintroduced to the wild; plans called for local breeding facilities in Dar es Salaam and Kihansi, screening for chytrid strains and pesticide residues, and soft releases tentatively by December 2010, guided by IUCN protocols. Major difficulties included persistent gaps in understanding the original chytrid outbreak's cause, ongoing local threats like wildfires and stream-side cultivation, and unresolved risk from dam-flushing releases of the pesticide endosulfan. The project rates itself Partially Successful, citing the rebuilt captive population as its clearest achievement so far.