Nsoung Long-fingered Frog
(Cardioglossa trifasciata)
The Nsoung long-fingered frog is a small grey, black and blue species that lives along high altitude mountain streams that run through shrub and montane forest vegetation. They shelter in cavities along the stream bank or under large stones. Males call along the stream for mates, and breeding is presumed to occur in the stream, with eggs hatching out into tadpoles. Mating calls are particularly frequent during the dry season and start at dawn. The habitat of this species is not especially threatened at present, but it remains at severe risk of extinction in the future given its very small range and vulnerability to agricultural encroachment, wood extraction, and expanding human settlements.
Urgent Conservation Actions
Remaining habitat in the only known area for the Nsoung long-fingered frog needs to be protected in a way that takes into account the needs of local communities.
Mount Manengouba in western Cameroon
The Nsoung long-fingered frog is names after the village of Nsoung, which is the nearest settlement to its distribution on Mount Manengouba in Western Cameroon.
Evolutionary Distinctiveness
Order: Anura
Family: Arthroleptidae
The genus Cardioglossa (commonly known as the long-fingered 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, with the long-fingered frogs diverging soon after. 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 15 known species of long-fingered frog and they are unusual among the squeaker frogs because they 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.
The Nsoung long-fingered frog is a fairly small species, adult females measuring between 24.5 to 28.5 mm. Long-fingered frogs are characterised by having exceptionally long third fingers with 15-20 small tooth-like structures of the skin (or dermal denticles) along the middle of this digit. The pattern across the back varies between individuals, and basically consists of large back markings that vary in their degree of separation. Some individuals may possess 3-4 blotches starting at their nose and finishing at the base of their back, whilst in others these blotches have become joined to form a continuous thick black band. The background colouration of the back is grey and the ventral (or lower) surface is blue.
Very little is known about this species because it have been little studies since it was officially described as a new species in 1972. It is known only from one locality, on the southern slopes of Mount Manengouba, below the village of Nsoung. The stream where it is located is small and runs through dense Ericaceous scrub (a common bushy vegetation type to be found at high altitudes indicating acid soils) and montane forest.

Males have been found to be very vocally active along the sides of the stream. They hide in small cavities along the stream bank, and the very young frogs also find refuges close to the stream. This species presumably breeds in streams, laying eggs which hatch into tadpoles before developing into froglets that hide in small cracks along the stream bank. It is important to note that the most calls can be heard in the dry season during the early mornings when it is very sunny. The calling starts at dawn, but may also continue into the day during the wet season when there is much cloud cover. This species only frequents little streams that are very enclosed in dense forest. Nsoung long-fingered frogs have also been found hidden under large rocks and small stones.
The Nsoung long-fingered frog has been found in and around a small stream running through dense secondary bush and montane forest, but has not been recorded from primary forest, although it might well occur there also. The difference between primary and secondary forest is that secondary forest is considered to be regenerates vegetation cover following forest clearance. Primary forest is a more mature ecosystem that has reached a stable assemblage of species, or “climax community”. Often in forests, secondary systems contains more undergrowth because the light has not been blocked out by the development of a close canopy of trees. This can be advantageous for amphibians that seek places to hide from predators. The secondary bush on the southern slopes of Mount Manengouba at 1,700-1,800 metres above sea level is mainly Ericaceous scrub, which often grows at high altitudes.
This species is known only from the southern slopes of Mount Manengouba in western Cameroon, at an altitude of 1,750-1,800 metres above sea level.
Population Estimate
Very little is known about this species and so there is no information available on its current population status.
Population Trend
The Nsoung long-fingered frog is considered to be in decline by the IUCN Red List of Threatened Species.
The Nsoung long-fingered 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., its distribution is severely fragmented, and the extent and quality of its forest habitat on Mount Manengouba is declining.
The habitat of this species is not especially threatened at present, but it remains at severe risk of extinction in the future given its very small range and vulnerability to agricultural encroachment, wood extraction, and expanding human settlements.
Conservation Underway
The Nsoung long-fingered frog is not known from any protected areas, and there are currently no conservation measures ongoing for this species.
Conservation Proposed
Remaining habitat in the only known area for the Nsoung long-fingered frog needs to be protected as a matter of urgency. This should take into account the needs of local communities and sustainable and ecologically sensitive solutions to issues such as wood extraction and agricultural expansion must be sought to find workable solutions to the conservation of this area.

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 Nsoung long-fingered frog is categorised as Critically Endangered, the possibility of a captive breeding programme for this species should be investigated.
Amiet, J.-L. 1972. Description de cinq nouvelles especes camerounaise de Cardioglossa (Amphibiens Anoures). Biol. Gabonica 8: 201-231.

Amiet, J.-L. 1972. Les Cardioglossa camerounaises. Science et Nature 114: 11-24.

Amiet, J.-L. 1973. Voix d'Amphibiens camerounais. II - Arthroleptinae: genre Cardioglossa. Ann. Fac. Sci. Cameroun 14: 149-164.

Amiet, J.-L. 1975. Ecologie et distribution des amphibiens anoures de la region de Nkongsamba (Cameroun). Ann. Fac. Sci. Yaounde 20: 33-107.

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

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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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