Alsco Long-fingered Frog
(Cardioglossa alsco)
The Alsco long-fingered frog is named after the company that funded the expedition that led to its formal discovery: American Linen Supply Company (ALSCO). This small tan, black, pink and blue frog is found in streams surrounded by remnant areas of forest, where it breeds and spends much of its time hiding under large stones in shallow creeks. When first discovered by scientists, it was observed in high densities – 73 individuals were collected during the first known sampling effort. The remaining forest habitat on Tchabal Mbabo is now confined to galleries and steep inaccessible slopes, as a result of the clearance of forest for pasture. These remnant areas are now threatened by fire.
Urgent Conservation Actions
A protected area has been recommended for Tchabal Mbabo to conserve the forest remnants; reforestation and habitat restoration around the area.
Mount Tchabal Mbabo in western Cameroon
The scientific name of this species is the acronym for the American Linen Supply Company (ALSCO) the German branch of which supported the expedition to the Tchabal Mbabo area where this species was discovered. The scientist who originally described this species names it after the company in acknowledgement of this support.
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.
This is a medium sized species, the male measuring 30 mm in total length and the females being slightly larger at 34 mm. The digits are long and thin with only slight webbing. 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 skin of the back is smooth but becomes increasingly granulates towards the bottom, and the skin of the stomach is smooth. The back is a tan brown colour with large, faded dark blotches. A broad black band extends along the side of the body from the tip of the nose to the base of the back. This band also passes across the eye, with only the top third of the iris being bronze and the rest being black. The flanks are pinkish-white and the arms and legs are tan on their upper surface with thin, broken black banding. The lower surface (stomach chest an throat area) is blue with intense black speckling.
This species associated with streams in montane gallery forest, in which it presumably breeds by larval development. This means that the eggs hatch out into free-swimming tadpoles before metamorphosing into froglets. Individuals have been found under large stones around shallow pools adjacent to a creek.

Alsco long-fingered frogs have been observed calling for mates at night during the dry season. Long-fingered frogs are known to deposit their eggs under stones in shallow pools, and this species is known to breed in streams. The fact that they may often be found in high densities under the same stone suggests that they meet in breeding aggregations, although it could also be due to a lack of available refugia for these frogs.
This species lives in montane gallery forest, and is associated with streams. Gallery forests are remnant areas of trees that have survived the intensive deforestation of a 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. The Alsco long-fingered frog is often found under large stones around shallow pools adjacent to creeks in gallery forest habitat.
The Alsco long-fingered frog is a recently discovered species known only from the southern slopes of Mount Tchabal Mbabo at 1,700 - 2,100m asl on the Adamaoua Plateau in western Cameroon. It is unlikely to occur on the northern slopes, at least not at the elevation of the type locality, because the forest habitat on the northern slopes at this elevation is very different from the gallery forest on the southern slopes.
Population Estimate
This frog was only officially described as a new species in 2000 and has not been intensively studied. Consequently, there are no population estimates for this species, although it is likely to be common within its small range – 73 specimens were collected from a small area, suggesting a high concentration of animals.
Population Trend
The Alsco long-fingered frog is thought to be in decline by the IUCN Red List of Threatened Species.
Listed as Critically Endangered because its Area of Occupancy is probably less than 10km sq., all individuals are in a single sub-population, and the extent of its forest habitat is declining.
The remaining forest habitat on Tchabal Mbabo is now confined to galleries and steep inaccessible slopes, as a result of the clearance of forest for pasture. This means that much of the forested habitat that can be easily removed has now been cleared and the remnant areas may be relatively safe from further deforestation. The main threat to this relic forest is fire.
Conservation Underway
The Alsoc long-fingered frog is not known from any protected areas, and there are currently no conservation measures ongoing for this species.
Conservation Proposed
A protected area has been recommended for Tchabal Mbabo to conserve the forest remnants. In addition, it may be necessary to carry out reforestation and habitat restoration around the area to increase the available habitat for this, and other, species. 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 Alsco long-fingered frog is categorised as Critically Endangered, the possibility of a captive breeding programme for this species should be investigated.
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