This is the Kihansi spray toad, Nectophrynoides asperginis.
It is a small toad, at just 2 to 3 cm long, and yellowish in colour. Rather than laying eggs like most amphibians, female Kihansi spray toads give birth to fully developed, tiny young, called toadlets.
The species was only discovered in 1996, in the spray zone of the falls at Kihansi Gorge in the Southern Udzungwa Mountains, an area of high biodiversity 300 km inland from the central east African coast.
It was found during an environmental impact assessment for the building of a 180-mega-watt hydroelectric project, which had already been under construction in the area since 1994. The region’s mining and tourism industries had long suffered from a lack of dependable electricity supply, and the 275-million-dollar project was therefore seen as vital.
The discovery of the toad did not stop construction. When the dam was completed in 1999, the falls were reduced to a trickle, and the surrounding habitat immediately changed. Spray from the falls had previously allowed moss and other wetland vegetation to dominate the slopes of the gorge, but they quickly dried out. Forest plants started to take over, and the toad could no longer thrive. Its numbers began to drop.
In 2000, a plan was put in place to install an extensive sprinkler system - at that time the world’s largest - to emulate the mist from the falls. 499 toads were also removed from the site and flown to a zoo in North America, to be kept as an insurance population. It was clear the species was in grave danger.
The sprinkler system at Kihansi Gorge was prone to malfunction and provided only intermittent spray, but for a time the toads survived. In 2003, however, the population suddenly collapsed. The toads were stressed by the constantly changing conditions, which allowed infection by a chytrid fungus to take hold.
In 2004, it was reported that no individuals of this species could be found at the gorge, and the Kihansi spray toad was declared “extinct in the wild” in 2009.
The captive population, meanwhile, suffered many setbacks, succumbing to various ailments including lungworm, metabolic bone disease, hypovitaminosis A, short tongue syndrome, bacterial sepsis, and chronic bloating linked to renal disease. In 2004, as the Kihansi spray toad disappeared from the wild, the captive population was down to just 70 individuals.
Great care was taken to overcome these early problems. Strict biosecurity protocols were enforced in the facility. Each terrarium contained a mister, appropriate vegetation, UV lighting, and precise temperature and humidity control. The toads received intensive medical care including regular fecal tests and skin swabbing to determine infection, and they were fed a diet of live insects, which were bred on site.
Year by year, their numbers increased to the thousands. In 2012, with new, reliable sprinkler infrastructure in place, reintroduction of the species at Kihansi Gorge was attempted. It was not successful - none of the toads survived. Subsequent trials in 2013, 2015 and 2016 also failed. After several generations in terrariums, the Kihansi spray toad had forgotten how to hunt and avoid predators, and it had no immunity to local pathogens.
In another attempt beginning in 2017, the toads were instead placed into large acclimation enclosures at Kihansi Gorge, in a wild-like environment where they also received medical care and protection from predators. They remain there to this day. It is hoped that over months and years, the group’s lost behaviours will be gradually relearnt.
Eventually, they will be released from the acclimation cages. However, as long as the dam remains, their existence will be completely dependent on the functioning of the artificial misters. Pesticide levels in the water, the presence of chytrid fungus and invasive predators, and other conditions must also be continuously monitored.
