74.
Nganha Night Frog
(Astylosternus nganhanus)
CR
Overview
This species is only known from five specimens and very little is understood about its behaviour and ecology. Tadpoles (almost certainly of this species) have been found in rock pools in streams, which indicates that, unlike many other squeaker frogs, Nganha night frog eggs do not hatch out into froglets via “direct development”. It is found along watercourses in a few narrow gallery forests, and in seepage areas in nearby grassland. This poorly known species is probably at severe risk from habitat loss.
Urgent Conservation Actions
Protection of the remaining habitat; survey work to establish the current population status; development of a Conservation Action Plan for this species.
Distribution
Mount Nganha on the Adamaoua Plateau in western Cameroon
Evolutionary Distinctiveness
Order: Anura
Family: Arthroleptidae
The genus Astylosternus (commonly known as the night frogs) is present in a family called the Arthroleptidae, or squeaker frogs. This is a fairly small family which contains (depending upon which family tree you consult) between about 50 and 129 known member species, all found across Africa below the Sahara desert. The family gets its common name from the distinctive calls of its constituent members, which are very similar to the sounds made by crickets. They are also sometimes caller “screechers”.

The squeaker frogs are closely related to the “true frogs” in the family Ranidae, and diverged from all other frog families about 75 million years ago in the Late Cretaceous. This was 10 million years before the extinction of the dinosaurs, making them as different from their closest relatives as camels are to whales! There are only 11 known species of night frog, and they are unusual among the squeaker frogs because they are presumed to lay eggs that hatch into tadpoles. Many other squeaker frogs have eggs that undergo “direct development” – meaning they hatch into miniature adults, avoiding any tadpole phase outside of the egg.
Description
The Nganha night frog is a fairly small frog, about 45 mm in total length. The head is very narrow, and is triangular and flattened in shape with rather small eyes that do not protrude greatly. The fingers are fairly short and slender. The hind-limbs are proportionally rather short and the ends of the toes are not dilates into discs. The skin of the body is smooth, except for some longitudinal fine wrinkles, especially on the sides of the body. The colouration of this species is dark with black patterning. The top of arms and fore-arms have large raised black bumps, but the thighs, unlike the rest of the body, do not have many markings. Dark pigmentation is also present under the throat and along the ventral (or lower) surfaces.
Ecology
This is a poorly known species and very little information has been collected about its behaviour and ecology. Tadpoles, almost certainly of this species, have been found in rock pools in streams, which indicates that, unlike the majority of squeaker frogs, Nganha night frog eggs do not hatch out into froglets via “direct development”.
Habitat
This species is found along watercourses in a few narrow gallery forests, and in seepage areas in nearby grassland. Gallery forests are remnant areas of trees that have survived the intensive deforestation of an area as a result of their inaccessible location – it is difficult to access because it is bordered by steep slopes, e.g. in gorges along streams.
Distribution
This species is restricted to Mount Nganha on the Adamaoua Plateau in western Cameroon, at an altitude of at 1,400-1,700 metres above sea level.
Population Estimate
This species is only known from five specimens and so there is insufficient information to formulate a population estimate.
Population Trend
This species is thought to be in decline by the IUCN Red List of Threatened Species.
Status
The Nganha night frog is listed as Critically Endangered in the IUCN Red List of Threatened Species because its extent of occurrence is probably less than 100 km sq. and its area of occupancy is probably less than 10 km sq., all individuals are in a single subpopulation, and the extent of its habitat on Nganha Mountain is probably declining.
Threats
This poorly known species is probably at severe risk from habitat loss.
Conservation Underway
The Nganha night frog is not known from any protected areas, and there are currently no conservation measures underway fro this species.
Conservation Proposed
Protection of the remaining habitat in the range of this species is urgently needed. Further survey work is required to establish the current population status of the Nganha night frog, and any information collected should be used to develop a Conservation Action Plan for this species.

In addition to conserving native habitat for this species, the IUCN Technical Guidelines for the Management of Ex situ Populations, part of the IUCN Red List of Threatened Species, recommend that all Critically Endangered species should have an ex situ population managed to guard against the extinction of the species. An ex situ population is ideally a breeding colony of a species maintained outside of its natural habitat, giving rise to individuals from that species that are sheltered from problems associated with their situation in the wild. This can be located within the species’ range or in a foreign country that has the facilities to support a captive breeding programme for that species. Since the Nganha night frog is categorised as Critically Endangered, the possibility of a captive breeding programme for this species should be investigated.
Links
References
Amiet, J.-L. 1977. Les Astylosternus du Cameroun (Amphibia, Anura, Astylosterninae). Ann. Fac. Sci. Yaounde 23-24: 99-227.

Amiet, J.-L. 2004. Astylosternus nganhanus. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. IUCN Red List of Threatened Species. Downloaded on 31 July 2007.

AmphibiaWeb: Information on amphibian biology and conservation [web application]. 2006. Berkeley, California: AmphibiaWeb. Available: amphibiaweb. Accessed: 08 December 2006.

Duellman, W. E. and Trueb, L. 1986. Biology of Amphibians. McGraw-Hill, New York.

Frost, Darrel R. 2006. Amphibian Species of the World: an Online Reference. Version 4 (17 August 2006). Electronic Database accessible at: . American Museum of Natural History, New York, USA.

Frost, D. R., Grant, T., Faivovich, J., Bain, R.H., Haas, A., Haddad, C. F. B., De Sá, R.O., Channing, A., Wilkinson, M., Donnellan, S.C., Raxworthy, C.J., Campbell, J.A., Blotto, B.L., Moler, P., Drewes, R.C., Nussbaum, R.A., Lynch, J.D., Green, D.M., and Wheeler, W.C. 2006. The Amphibian Tree of Life. Bulletin of the American Museum of Natural History 297: 1-370.

Halliday, T. and Adler, C. (eds.). 2002. The new encyclopedia of reptiles and amphibians. Oxford University Press, Oxford.

IUCN, Conservation International and NatureServe. 2006. Global Amphibian Assessment. Global Amphibian Assessment. Accessed on 08 December 2006.

Mattison, C. 1987. Frogs and toads of the world. Blandford Press, U.K.

Obst, F.J., Richter, K. and Jacob, U. 1984. The Completely Illustrated Atlas of Reptiles and Amphibians for the Terrarium. T.F.H. Publication Inc., N.J., U.S.A.

Roelants, K., Gower, D. J., Wilkinson, M., Loader, S. P., Biju, S. D., Guillaume, K., Moiau, L. and Bossuyt, F. 2007. Global patterns of diversification in the history of modern amphibians. Proceedings of the National Academy of Sciences 104: 887-892.

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