Description
Kihansi spray toads are tiny, with adults measuring 10 - 18 mm snout-vent length. The overall background color is yellow/golden, with yellow and brown speckles on the dorsal surface, or dark lateral bands with adjacent lighter striping. Ventrally the skin is translucent whitish near the throat and posterior, with the liver, fat bodies, and intestines visible through the ventral skin. Gravid females also have a bluish-green cast to the abdominal wall, due to the developing larvae pressing up against the skin. These toads have flaps over the nostrils that may be a special adaptation for living in the spray zone of waterfalls. On the feet, toes are partially webbed. No external tympana are present (Poynton et al. 1998; Lee et al. 2006).

Females are slightly larger than males but morphologically difficult to distinguish unless gravid, when the females become more rotund (Lee et al. 2006). Males have somewhat more dark pores dorsally, especially around the head and shoulders (Lee et al. 2006). Breeding males in captivity have been observed to develop dark patches of interfemoral glands, in the inguinal cavities (on the lateral surfaces of the body and thighs, where they meet) (Poynton et al. 1998).

No free-living tadpole stage is present since this species is a direct developer. Newly hatched froglets are 5 mm in snout-vent length, and are dark gray dorsally with white ventral skin. As juveniles grow, lateral blue-gray streaks develop, along with striations on the head. In captivity, the yellow ground color and brown striping develop at about 6 - 8 weeks of age, along with sacral V-shaped marks (Poynton 1998).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Tanzania, United Republic of

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (12 records).

This toad is known only from one location encompassing about 2 hectares, the Kihansi River Gorge upper falls spray wetland in the Udzungwa Mountains, Tanzania. It has been found at several sites within the spray zone along the escarpments of the Gorge, in rocky, mist-shrouded wetland spray meadow. Vegetation includes club moss (Selaginella kraussiana), snail ferns (Tectaria gemmifera) and low grasses (Panicum spp.) (Poynton et al. 1998).

Life History, Abundance, Activity, and Special Behaviors

This species is ovoviviparous and a direct developer, meaning that there is no free-living tadpole stage; fertilization is internal and larvae are retained within the female, with juvenile toadlets being born through the female's cloaca (Lee et al. 2006; Orton 1949). Eggs are 2.4 mm in diameter (Poynton et al. 1998). Although Lee et al. (2006) reported that the clutch size may be as large as 24 - 28 eggs, Channing et al. (2006) state that clutch size varies from 5 - 13 offspring.

The male's dark interfemoral gland patches may produce both pheromones and a visual cue to signal territoriality to other males. In captivity, males have been observed stretching the rear legs out behind them and presenting patches, often while vocalizing. Axillary amplexus has been observed in captivity, and there is also a single report of ventrally opposed amplexus (Lee et al. 2006).

In captivity, this species has been observed feigning death when disturbed. It may also eject water from the bladder after being disturbed (Lee et al. 2006).

Stomach content analysis indicates that wild Kihansi spray toads prefer to feed on dipterids and dipterid larvae, but also consume some acarine mites as well as springtails (Lee et al. 2006).

Sympatric species include Arthroleptis stenodactylus, Schoutedenella xenodactyla, Nectophrynoides tornieri, and Arthroleptides spp. (NORPLAN 2002, cited in Lee et al. 2006).

Trends and Threats
In 1999, over 20,000 toads were estimated to be present in the Upper Spray Wetland region alone, but by January 2004, only three were seen in the wild with another two males heard calling (Lee et al. 2006). There was an unconfirmed report from May 2005 (CBSG 2007), but none have been seen since despite surveys of its very limited range. This species was classified as Extinct in the Wild in 2009 (Channing et al. 2009). Captive populations are being maintained in zoos.

The construction of a massive hydroelectric dam ($270 million US, funded by loans from the World Bank) caused the site to become considerably drier in early 2000 (Quinn et al. 2005). Brief experiments with high-flow water release were conducted in 2002 and late spring 2003 (Lee et al. 2006). In October 2000, it was estimated that 11,400 toads were present in five wetland areas (Upper, Lower, Mhalala, Mid-Falls, and Mid-Gorge Spray Wetlands; NORPLAN 2002, cited in Lee et al. 2006). Between Dec. 2002 and June 2003 the population was estimated to be 8,000 - 17,000 toads. In June 2003, one week after the last high-flow release experiments were conducted, only 43 Kihansi spray toads were seen in the area. In January 2004, three Kihansi spray toads were observed and two males were heard vocalizing, for a total of five toads (Lee et al. 2006). Although there is one unconfirmed report from 2005 (CBSG 2007), no toads have been sighted or heard since (Channing et al. 2009).

To try to save the toads in the wild, a sprinkler system was deployed over about 1/4 of their habitat between July 2000 and March 2001 to mimic the natural spray from the waterfall. Despite the artificial sprinkler system, the plant species assemblage changed and within 18 months the marsh and stream-side plants had retreated, with weedy species proliferating (Quinn et al. 2005). Thus the habitat was irreversibly altered by the dam (Lee et al. 2006).

Factors also associated with the population crash are chytrid fungus (Batrachochytrium dendrobatidis) and pesticides used upstream, but these factors are considered secondary to the effects of the dam cutting off the waterfall spray (Quinn et al. 2005, Krajik 2006).

Fearing the toads would go extinct, the Tanzanian government and the Wildlife Conservation Society collected a total of 499 animals from two localities for captive breeding, in late 2000. About 460 individuals, most captive-bred, survive in two zoos in the United States, the Toledo Zoo, in Ohio, and the Bronx Zoo, in New York (CBSG 2007). In 2010, a captive population was established in Tanzania by National Environmental Management Council and University of Dar Salaam researchers. As of Dec 2012, the captive populations were estimated to have over 6,000 individuals (IUCN 2012).

By 2010, suitable habitat was restored by the sprinkler system and habitat restoration. On 29 October 2012, the IUCN Species Survival Commission (specifically their Amphibian Specialist Group and Re-introduction Specialist Group) released 2,500 individuals back into the wild with more individuals slated for release (IUCN 2012).

Relation to Humans
The decline of this species was unintentionally caused by human alteration of the environment. Efforts to keep the toad from going extinct have illustrated just how difficult it is to reverse a near extinction.

Possible reasons for amphibian decline

Dams changing river flow and/or covering habitat
Long-distance pesticides, toxins, and pollutants
Disease

References

CBSG (IUCN/SSC). 2007. Kihansi Spray Toad (Nectophrynoides asperginis) Population and Habitat Viability Assessment: Briefing Book. CBSG, Apple Valley.

Channing, A., Finlow-Bates, K. S., Haarklau, S. E. and Hawkes, P. G. (2006). ''The biology and recent history of the Critically Endangered Kihansi Spray Toad Nectophrynoides asperginis in Tanzania.'' Journal of East African Natural History, 95, 117-138.

Channing, A., Howell, K., Loader, S., Menegon, M. and Poynton, J. 2009. Nectophrynoides asperginis. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2. www.iucnredlist.org. Downloaded on 05 January 2010.

IUCN (2012). ''Kihansi Spray Toad returns to the wild'' https://www.iucn.org/content/kihansi-spray-toad-returns-wild. Downloaded on 16 October 2018.

Krajik, K. (2006). ''The lost world of the Kihansi Toad: NewsFocus.'' Science, 311, 1230-1232.

Lee, S., Zippel, K., Ramos, L., and Searle, J. (2006). ''Captive-breeding programme for the Kihansi spray toad Nectophrynoides asperginis at the Wildlife Conservation Society, Bronx, New York.'' International Zoo Yearbook, 40, 241-253.

NORPLAN (2002). Lower Kihansi Hydropower Project: immediate rescue and emergency measures. Final specialist report: amphibian studies. Report produced for Tanzania Electric Supply Company Ltd. (TANESCO), Dar es Salaam, Tanzania.

Orton, G.L. (1949). "Larval development of Nectophrynoides tomieri (Raux), with comments on direct development in frogs." Annals of the Carnegie Museum, 31, 257-278.

Poynton, J. C., Howell, K. M., Clarke, B. T., and Lovett, J. C. (1998). ''A critically endangered new species of Nectophrynoides (Anura: Bufonidae) from the Kihansi Gorge, Udzungwa Mountains, Tanzania.'' African Journal of Herpetology, 47, 59-67.

Quinn, C. H., Ndangalasi, H. J., Gerstle, J., and Lovett, J. C. (2005). ''Effect of the Lower Kihansi Hydropower Project and post-project mitigation measures on wetland vegetation in Kihansi Gorge, Tanzania.'' Biodiversity and Conservation, 14, 297-308.

Species Account Citation: AmphibiaWeb 2023 Nectophrynoides asperginis: Kihansi Spray Toad <https://amphibiaweb.org/species/5397> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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