Kihansi spray toad (Nectophrynoides asperginis)

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Kihansi spray toad
IUCN Red List species status – Extinct in the Wild EXTINCT
IN THE WILD

Top facts

  • A tiny toad of just two centimetres in length, the Kihansi spray toad is endemic to a two-hectare area of Kihansi Gorge in Tanzania.
  • Once considered to be extinct in the wild, the Kihansi spray toad has been the subject of intensive conservation measures and has now been successfully reintroduced to the wild.
  • The Kihansi spray toad has yellow or golden skin speckled with yellow and brown marks on the upperparts and with translucent-white skin on the underside.
  • Interestingly, the Kihansi spray toad does not have a tadpole stage, with the female giving birth to live toadlets.
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Kihansi spray toad fact file

Kihansi spray toad description

KingdomAnimalia
PhylumChordata
ClassAmphibia
OrderAnura
FamilyBufonidae
GenusNectophrynoides (1)

First discovered and described in the mid- to late 1990s (3) (5), the Kihansi spray toad is a tiny amphibian with yellow or golden skin speckled with yellow and brown marks on the upperparts. Some individuals of this species may have dark bands along the sides which are bordered by paler striping (2).

The underside of the Kihansi spray toad is translucent-whitish, and organs such as the liver and intestines can be seen through the skin. In gravid females, the developing larvae press up against the skin of the toad’s underside, giving it a bluish-green hue (2). Male and female Kihansi spray toads are generally similar in appearance, although the females are usually slightly larger than the males (2) (3), and are typically more rotund when gravid (2). The male sometimes has more dark pores around its head and shoulders, and may develop dark patches at the tops of its thighs during the breeding season (2).

Interestingly, the Kihansi spray toad is reported to have flaps over its nostrils, which are thought to be a special adaptation for surviving in the amphibian’s waterfall spray zone habitat. The toes of this species are partially webbed (2).

Newly hatched Kihansi spray toads are dark grey (2) or purplish (3) on the upperparts and have white undersides, developing blue-grey streaks on the sides and head as they develop (2). In captivity, young Kihansi spray toads develop the yellow skin colouring and brown striping at about six to eight weeks of age (2).

The call of the Kihansi spray toad is described as being soft and simple, consisting of short call notes, parts of which are out of the range of human hearing (6).

Size
Adult snout-vent length: 1 - 2 cm (2) (3)
Average weight: 0.3 - 0.66 g (3)
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Kihansi spray toad biology

The Kihansi spray toad is a diurnal species (6) which is known to feed on small insects (3), including flies and fly larvae. It also eats some mites and springtails (2). In captivity, the Kihansi spray toad has been known to feign death or eject water from its bladder when disturbed (2).

This species is thought to reproduce at about nine months old (3), breeding by internal fertilisation (1) (2). It is thought that the male Kihansi spray toad may produce pheromones in glands located under patches between the thighs and the body, and in captivity males have been observed stretching their hind legs out behind them to display the patches as they call. As in many amphibians, the Kihansi spray toad mates in amplexus (2).

An ovoviviparous species, the Kihansi spray toad gives birth to live young, bypassing the tadpole stage (2) (3). The toad larvae are retained internally by the female, and little toadlets are born (1) (2), which are usually about five millimetres in length (2). Clutch size usually varies between 5 and 13 offspring (1) (2), although may be as large as 24 in the wild and 28 in captivity (2) (3).

Observations of the Kihansi spray toad’s social interactions indicate that this species has adapted to the high volume of ambient noise produced by the waterfalls by communicating at short-range when in visual contact with a conspecific (6).

The lifespan of the Kihansi spray toad in the wild is unknown, but in captivity this rare species has been recorded living to about three years of age (3).

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Kihansi spray toad range

As its name suggests, the Kihansi spray toad is endemic to the Kihansi Falls of the Kihansi River Gorge in the Udzungwa Mountains of eastern Tanzania (1) (2) (3) (5) (6). This species was previously known only from a two-hectare area (1) (2).

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Kihansi spray toad habitat

The Kihansi spray toad has very specific habitat requirements, being found only in rocky wetland spray meadows of upper waterfalls (1) (2) (5) (6). These areas are moistened by natural mists from the rapid waterfalls (2) (3), which create conditions of high humidity and low temperature (3). The preferred habitat of the Kihansi spray toad is dominated by moss-covered rocks and mossy vegetation (3), including club moss (Selaginella kraussiana) (2), and occurs at elevations between 600 and 940 metres (1).

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Kihansi spray toad status

The Kihansi spray toad is classified as Extinct in the Wild (EW) on the IUCN Red List (1), and is listed on Appendix I of CITES (4).

IUCN Red List species status – Extinct in the Wild

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Kihansi spray toad threats

A key factor in the dramatic decline of the Kihansi spray toad is believed to be the construction in 2000 of a dam upstream of the toad’s habitat as part of the Lower Kihansi Hydropower Project to produce electricity. This development cut off 90 percent of the original water flow in the area, reducing the volume of spray being produced by the falls, particularly during the dry season (1) (2) (3) (5). The reduction in available moisture led to a change in the composition of the wetland vegetation (1) (3), enabling the overgrowth of other plant species which previously remained in the forest (3).

In addition, the construction of the dam is believed to have reduced the water quality in the region (3). From an estimated 20,000 or more Kihansi spray toads in 1999 in the Upper Spray Wetland alone, the population suffered a devastating decline and by January 2004 only 3 individuals were seen in the wild (1) (2). No further Kihansi spray toads were sighted after this (1), and the species was declared Extinct in the Wild in 2009 (2).

Other factors implicated in the Kihansi spray toad population crash include the arrival of the deadly chytrid fungus Batrachochytrium dendrobatidis (1) (2) (3), which may have been introduced by construction workers when building the dam, as well as the encroachment of non-native plants (3) and the use of pesticides upstream (1) (2).

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Kihansi spray toad conservation

The Kihansi spray toad is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which means that international trade in this species is strictly prohibited (4). Unfortunately, the Kihansi spray toad is not known from any protected areas (1), but thankfully fears that the toad might go extinct spurred the Tanzanian government and the Wildlife Conservation Society into collecting 499 individuals in 2000 for a captive breeding programme (2). There is currently ongoing work at Toledo Zoo, Ohio, and the Bronx Zoo, New York, to breed this rare species (1) (3). Although several husbandry issues were initially encountered, including nutritional deficiencies and diseases, these have since been addressed and the breeding programme is progressing well (1) (2), with more than 6,000 captive individuals raised by 2012 (7).

In an attempt to save the dwindling wild population of Kihansi spray toads, a special sprinkler system was developed and deployed during 2000 and 2001 at three wetland meadows to try and mimic the natural mists previously produced by the rapid waterfalls (1) (3).

Other conservation measures put into place included implementing various field studies, such as assessments of the Kihansi spray toad’s diet, studying the microclimate and vegetation of the gorge, screening toads for the chytrid fungus, and constructing bridges and walkways within the toad’s habitat to prevent trampling damage. Work was also undertaken to establish the required water flow levels in the gorge. All of these measures provided invaluable data for the long-term conservation of the Kihansi spray toad (3).

In 2012, 2,500 Kihansi spray toads were flown from captive breeding facilities in the USA to Tanzania, where some individuals were released into the wild after a period of acclimatisation. More releases are expected in the future (7).

View information on this species at the UNEP World Conservation Monitoring Centre.
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Find out more

Find out more about the Kihansi spray toad:

Learn more about amphibians and their conservation:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Amplexus
The mating position of frogs and toads, in which the male clasps the female around the back or waist.
Diurnal
Active during the day.
Endemic
A species or taxonomic group that is only found in one particular country or geographic area.
Fertilisation
The fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.
Gland
An organ that makes and secretes substances used by the body.
Gravid
Carrying developing young or eggs.
Larva
Immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.
Ovoviviparous
Producing young that develop inside eggs, but the eggs hatch inside the female’s body and the young are born live.
Pheromone
A chemical produced by an animal, which stimulates a behavioural or physiological response by another member of the same species.
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References

  1. IUCN Red List (October, 2013)
    http://www.iucnredlist.org/
  2. AmphibiaWeb - Nectophrynoides asperginis (October, 2013)
    http://www.amphibiaweb.org/cgi/amphib_query?where-genus=Nectophrynoides&where-species=asperginis
  3. Rija, A.A., Khatibu, F.H., Kohi, E.M. and Muheto, R. (2011) Status and reintroduction of the Kihansi spray toad Nectophrynoides asperginis in Kihansi gorge: challenges and opportunities. Proceedings of the 7th TAWIRI Scientific Conference, 2-4 December 2009, Arusha, Tanzania: 11-20.
  4. CITES (October, 2013)
    http://www.cites.org/
  5. Natura lHistory Museum- Nectophrynoides asperginis (October, 2013)
    http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/endangered-species/nectophrynoides-asperginis/index.html
  6. Arch, V.S., Richards-Zawaki, C.L. and Feng, A.S. (2011) Acoustic communication in the Kihansi spray toad (Nectophrynoides asperginis): Insights from a captive population. Journal of Herpetology, 45(1): 45-49.
  7. IUCN News - Kihansi Spray Toad returns to the wild (October, 2013)
    http://www.iucn.org/news_homepage/?11673/Kihansi-Spray-Toad-returns-to-the-wild
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Image credit

Kihansi spray toad  
Kihansi spray toad

© Danté B Fenolio

Dante Fenolio
dante@anotheca.com

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