The Kihansi spray toad (Nectophrynoides asperginis) is a small toad endemic to Tanzania. The species is live-bearing and insectivorous. The Kihansi spray toad is currently categorized as Extinct in the Wild by the International Union for Conservation of Nature (IUCN), though the species persists in ex situ, captive breeding populations.
Physiology
The Kihansi spray toad is a small, sexually dimorphic anuran, with females reaching up to long and males up to . The toads display yellow skin coloration with brownish They have webbed toes on their hind legs, but lack expanded toe tips. They lack external ears, but do possess normal anuran inner ear features, with the exception of tympanic membranes and air-filled middle ear cavities. Females are often duller in coloration, and males normally have more significant markings Additionally, males exhibit dark inguinal patches on their sides where their hind legs meet their abdomens. Abdominal skin is translucent, and developing offspring can often be seen in the bellies of gravid females. The toad breeds by using internal fertilization, in which females retain larvae internally in the oviduct until their offspring are born.
Habitat
Prior to its extirpation, the Kihansi spray toad was endemic only to a area at the base of the Kihansi River waterfall in the Udzungwa escarpment of the Eastern Arc Mountains in Tanzania. The Kihansi Gorge is about long with a north–south orientation. A number of wetlands made up the habitat of this species, all fed by spray from the Kihansi River waterfall. These wetlands were characterized by dense, grassy vegetation including Panicum grasses, Selaginella kraussiana clubmosses, and snail ferns (Tectaria gemmifera). Areas within the spray zones of the waterfall experienced near-constant temperatures and 100% humidity. Currently, an artificial gravity-fed sprinkler system is in place to mimic the original conditions of the spray zones. The species' global range covered an area of less than two hectares around the Kihansi Falls, and no additional populations have been located after searching for it around other waterfalls on the escarpment of the Udzungwa Mountains.
Extinction in the wild
Prior to extinction, there was a population of around 17,000 individuals and fluctuating naturally. The population hit a high in May 1999, dropped to lower numbers in 2001 and 2002, hit a high again in June 2003 (around 20,989 individuals), before steeply declining to a point in January 2004 when only three individuals could be seen and two males were heard calling. The species was listed as Extinct in the Wild in May 2009. The extinction in the wild of the Kihansi spray toad was mainly due to habitat loss following the construction of Kihansi Dam in 1999, which reduced the amount of water coming down from the waterfall into the gorge by 90 percent, hugely reducing the volume of the spray, particularly in the dry season, as well as altering vegetational composition. This led to the spray toad's microhabitat being compromised, as it reduced the amount of water spray, which the toads were reliant on. The sprinkler system that mimicked the natural water spray was not yet operational when the Kihansi Dam opened. In 2003 there was a final population crash in the species. This coincided with a breakdown of the sprinkler system during the dry season, the appearance of the disease chytridiomycosis, and the brief opening of the Kihansi Dam to flush out sediments, which contained pesticides used in maize farming operations upstream. The last confirmed record of wild Kihansi spray toads was in 2004.
Conservation efforts
Environmental management
Between July 2000 and March 2001, gravity-fed artificial spray systems were built and placed in three areas of spray wetlands that were affected by the Kihansi Dam. These spray systems functioned to mimic the fine water spray that had existed prior to the diversion of the Kihansi river, maintaining the microhabitat. The installation was initially successful in maintaining the spray-zone habitat, but after 18 months, marsh and stream-side plants retreated and a weedy species overran the area, changing the overall plant-species composition. The next steps in environmental management included ecological monitoring, mitigation, establishing rights of water authority and Tanesco to implement hydrological resources for conservation of the Kihansi spray toad and spray wetlands habitat.