The Amphibians of Mount Oku, Cameroon: an updated species inventory and conservation review

Abstract

Amphibians are a disproportionately threatened group of vertebrates, the status of which in Sub-Saharan Africa is still uncertain, with heterogeneous fauna punctuated by mountains. Mount Oku, Cameroon is one such mountain, which holds many endemic and restricted-range species. The history of amphibian research on Mt Oku, current knowledge on biogeography and conservation biology is reviewed, including recent findings. This updated inventory adds 25 further species, with 50 species of amphibian so far recorded to the Oku Massif (c. 900 to 3,011 m). This includes 5 endemic to Mt Oku, 7 endemic to the Bamenda Highlands, 18 restricted to the highlands of Cameroon and Nigeria, and 20 with broader ranges across Africa. This includes a new mountain locality for the Critically Endangered Leptodactylodon axillaris. Among others, the first record of Phrynobatrachus schioetzi and Ptychadena taenioscelis from Cameroon are presented. The uncertainty of habitat affinities and elevational ranges are discussed. The proportion of threatened species on Mt Oku is 44.2%, but projected to increase to 47.9% due to new species descriptions and recent dramatic declines. The natural habitats of Mt Oku are irreplaceable refuges for its endemic and restricted-range amphibian populations under severe pressure elsewhere in their range. Threats to this important amphibian fauna are increasing, including agricultural encroachment, expanding aquaculture, livestock grazing, pollution, invasive species, forest loss and degradation. Past, present and desired conservation interventions to address these threats are discussed.

Evolutionary history of the Cameroon radiation of puddle frogs (Phrynobatrachidae:Phrynobatrachus), with descriptions of two critically endangered new species from the northern Cameroon Volcanic Line

“…Phrynobatrachus mbabo was not found during a survey in June 2016, thus, the species was last seen in 2000, when the type material was collected. We presume that P. mbabo may be underlying a severe population decline like other montane Phrynobatrachus in the Cameroon Highlands (Hirschfeld et al, 2016;Doherty-Bone & Gvoždík, 2017;Tchassem et al, 2019). This is probably the reason why it was not found in 2016 as P. steindachneri was also not found.…”

“…Threat status: The species is of a high conservation concern. Phrynobatrachus is disappearing from the Cameroon Highlands (Hirschfeld et al, 2016;Doherty-Bone & Gvoždík, 2017;Tchassem et al, 2019), and it seems that this is also true for P. arcanus.…”

“…Similarly, G. Nikolaus collected only four specimens among 54 individuals of Phrynobatrachus in 1988 (the others being P. steindachneri-our investigation; Böhme & Nikolaus, 1989). Moreover, the failure to find this species in 2016 despite intensive searches may be related to a population decline, which is known to have occurred in Phrynobatrachus at different sites in the CVL (Hirschfeld et al, 2016;Doherty-Bone & Gvoždík, 2017;Tchassem et al, 2019). (Gosner, 1960), same collection data as holotype.…”

“…It is known only from high elevations of Mt. Oku (Zimkus, 2009;Pfalzgraff et al, 2015;Doherty-Bone & Gvoždík, 2017). On Mt.…”

“…At about 800-1,000 m the vegetation grades into the lowland coastal or more inland Congolian forest ecozones, or the Guineo-Congolian forest-savanna mosaic (Burgess et al, 2004). The natural habitats, mainly montane forests of the Cameroon Highlands, are highly threatened and are being lost due to intensive human activities, especially in the southern portion of the highlands (Cronin et al, 2014;Doherty-Bone & Gvoždík, 2017;Tchassem et al, 2019). The northern parts of the Cameroon Highlands (Mambilla Plateau, Gotel Mountains, Tchabal Mbabo, Tchabal Gangdaba, and Tchabal Nganha) are less densely populated and have always received less biological exploration and conservation attention (Cronin et al, 2014), probably due to their relatively remote locations with more difficult access.…”