Description
Astylosternus fallax is a long-bodied, West African frog that have males that range from 47.2 - 51.5 mm in snout–vent length with an average of 49 mm. The females are generally larger with a maximum of 64 mm and an average of 61 mm. This species has a broad head with a prominent, rounded canthus rostralis. The tympanic ridge is poorly developed and broken. The tympanum to eye ratio is 55.5%. The dorsal integument is conspicuously wrinkled and granulated, and the anterior limbs exhibit small tubercles. The toe tips are skinny, slightly dilated at the extremity with a moderate amount of webbing. The tubercles on the eyelid are small and preceded by large granulations. The males, during breeding season, have a double nuptial pad and no gular spines (Amiet 1977).

The adult dorsal coloration is brown, beige, or olive speckled with light spots and irregular, round, dark markings. The ventral coloration is bright yellow, turning to pink scattered with dark spots under the throat, and very little pigmentation on the legs. The hind limbs have two to six small transverse bands, and the forelimbs have two transverse bars which are less visible and interrupted (Amiet 1977).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Cameroon

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (9 records).

This species is found in the Cameroon Volcanic Line of western Cameroon. It is associated with hilly lowland forests up to about 1000 meters (Amiet 1977; Channing and Rödel 2019). Its presence has been confirmed through surveys in the following areas: Nkongsamba, Mount Yuhan in Korup National Park, and Mt. Nta Ali in the Mamfe basin (Amiet 1977; Lawson 1992), as well as on Mt. Nlonako (Plath et al. 2004; Herrmann et al. 2005).

Life History, Abundance, Activity, and Special Behaviors
The adults are nocturnal (Channing and Rödel 2019).

During the breeding season, males are found calling in leaf litter near rivers. The call is described as "oua-ha" or "oua-ha-ha" at an interval of two notes for 0.1 seconds (Channing and Rödel 2019).

On Mt. Nlonako, A. fallax has been found at the same sites as A. diadematus and A. perreti (Plath et al. 2004; Herrmann et al. 2005).

Larva
Tadpoles have a total length between 45 - 74 mm. The body length to total length ratio is 36.3 ± 2.6%. The ventral-fin-height to dorsal-fin-height ratio is 68.9 ± 11.5%. The anterior lip papillae are positioned laterally, and the posterior papillae are in 2 to 3 rows of 20 triangular papillae. The papillae of the inner row are shorter than the marginal row. The keratodont formula is 1:2+2/2+2:1. The rostral gap is large and the jaw sheaths are massive and serrated. The upper jaw has a medial fang, and the lower jaw is U-shaped with a broad medial notch (Griesbaum et al. 2019).

The tadpoles' coloration is pale brown and the dorsal surface is darker. The back and the tail have irregular, big, dark brown spots or blotches. The venter is pale with little or no dark speckling. Tail fins are beige and semi-transparent with dark brown spots. The jaw sheaths are black (Griesbaum et al. 2019).

Trends and Threats
This species has a decreasing population size due to loss of habitat caused by human settlement and agricultural encroachment. Human consumption may also be a threat (IUCN 2021).

Relation to Humans
It has not been confirmed but it may be consumed by humans (IUCN 2021).

Comments
Preliminary genetic studies have found two clades in the genus, a West African clade and a Central African clade (Portik et al. 2019). The phylogenetic placement of A. fallax likely falls into the Central African clade (Allen et al. unpublished data).

References

Amiet, J.-L. (1977). ''Les Astylosternus du Cameroun (Amphibia Anura, Astylosterninae).'' Annales de la Faculté des Sciences de Yaoundé, 23/24, 99-227.

Channing, A., Rödel, M.-O. (2019). Field Guide to the Frogs and Other Amphibians of Africa. Penguin Random House South Africa, Cape Town, South Africa.

Griesbaum, F., Hirschfeld, M., Barej, M. F., Schmitz, A., Rohrmoser, M., Dahmen, M., Mühlberer, F., Liedtke, H.C. Gonwouo, N.L., Doumbia, J., Rödel, M. O. (2019). "Tadpoles of three western African frog genera: Astylosternus Werner, 1898, Nyctibates Boulenger, 1904, and Scotobleps Boulenger, 1900 (Amphibia, Anura, Arthroleptidae)." Zoosystematics and Evolution, 95, 133–160. [link]

Herrmann, H.-W., Böhme, W., Herrmann, P.A., Plath, M., Schmitz, A., Solbach, M. (2005). ''African biodiversity hotspots: the amphibians of Mt. Nlonako, Cameroon.'' Salamandra, 41(1/2), 61–81.

IUCN SSC Amphibian Specialist Group. (2017). "Astylosternus fallax." The IUCN Red List of Threatened Species 2017: e.T54417A95841677. https://dx.doi.org/10.2305/IUCN.UK.2017-2.RLTS.T54417A95841677.en. Accessed on 09 February 2022.

Lawson, D. P. (1992). "The herpetofauna of Korup National Park, Cameroon: biogeography and comparative biodiversity of a tropical African rainforest." Doctoral dissertation, The University of Texas at Arlington

Plath M, Solbach M, Herrmann H-W (2004). ''Anuran habitat selection and temporal partitioning in a montane and submontane rainforest in southwestern Cameroon – first results.'' Salamandra (Frankf), 40, 239-260. [link]

Portik DM, Bell RC, Blackburn DC, Bauer AM, Barratt CD, Branch WR, Burger M, Channing A, Colston TJ, Conradie W, Dehlin JM, Drewes RC, Ernst R, Greenbaum E, Gvozdík V, Harvey J, Hillers A, Hirschfeld M, Jongsma GFM, Kielgast J, Kouete MT, Lawson LP, Leaché AD, Loader SP, Lötters S, van der Meijden A, Menegon M, Müller S, Nagy ZT, Ofori-Boateng C, Ohler A, Papenfuss TJ, Rößler D, SinschU, Rödel MO, Veith M, Vindum J, Zassi-Boulou AG, McGuire JA (2019). ''Sexual dichromatism drives diversification within a major radiation of African amphibians.'' Systematic Biology , 68(6), 859-875. [link]

Species Account Citation: AmphibiaWeb 2025 Astylosternus fallax <https://amphibiaweb.org/species/1482> University of California, Berkeley, CA, USA. Accessed Jun 13, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 13 Jun 2025.

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