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 2.9 cm (1.1 in) long and males up
to 1.9 cm (0.75 in). The toads display yellow skin coloration
with brownish dorsolateral striping. 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.
These toads 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.
Habitat
Prior to its extirpation, the Kihansi
spray toad was endemic only to a two hectare 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 4 km 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 moss, and snail ferns (Tectaria gemmifera).Areas within the spray zones of the waterfall experienced
near-constant temperatures and 100% humidity.
Extinction in the wild
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. This led to the spray toad's microhabitat being compromised, as it reduced
the amount of water spray, which the toads were reliant on. A 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. The last confirmed record of wild Kihansi spray toads
was in 2004.
Survival in captivity
The Bronx
Zoo initiated a
project where almost 500 Kihansi spray toads were taken from their native gorge
in 2001 and placed in six U.S. zoos as a possible hedge against
extinction. Initially its unusual life style and reproduction mode caused
problems in captivity, and only Bronx Zoo and Toledo
Zoo were able to
maintain populations. By December 2004, fewer than 70 remained in
captivity, but when their exact requirements were discovered greater survival
and breeding success was achieved. In November 2005, the Toledo Zoo opened
an exhibit for the Kihansi spray toad, and for some time this was the only
place in the world where it was on display to the public. The Toledo Zoo
now has several thousand Kihansi spray toads, the majority off-exhibit.
The Bronx Zoo also has several thousand Kihansi spray toads, and it opened
a small exhibit for some of these in February 2010. In 2010 Toledo Zoo
transferred 350 toads to Chattanooga Zoo, which
has created a small exhibit for them. Groups numbering in the hundreds are now
also maintained at Detroit
Zoo and Omaha's Henry Doorly Zoo.
Reintroduction
In August 2010, a group of 100 Kihansi
spray toads were flown from the Bronx Zoo and Toledo Zoo to their native
Tanzania, as part of an effort to reintroduce the species into the wild,
using a propagation center at the University of Dar es Salaam.[10][13] In 2012, scientists from the
center returned a test population of 48 toads to the Kihansi gorge, having
found means to co-inhabit the toads with the chytrid fungus. They plan to
release a total population of about 1,800 toads after monitoring the initial
release for several months. In 2017 a reintroduction program
will be launched and currently a few Kihansi spray toads will be successfully
reintroduced in Tanzania