Assessment of the distribution and conservation status of the viviparous toad Nimbaphrynoides occidentalis on Monts Nimba, Guinea

摘要

We investigated the distribution of the viviparous Nimba toad Nimbaphrynoides occidentalis throughout its potential range, the montane grasslands of the Monts Nimba massif, West Africa. Although predominantly part of a World Heritage Site, the Monts Nimba also comprise a mining enclave in the northwestern part of the mountain massif. The present study revealed that the Nimba toad seems to have its most viable populations within the mining enclave (Mont Sempéré) or directly adjacent to it (Grands Rochers). These 2 populations and a third, presumably isolated one (Mont Richard Molard), may be source populations, whereas other smaller populations are likely to be sinks. We generally recorded lower toad densities than in earlier studies and failed to confirm the toads’ presence in parts of their former known range. Some of these changes might be due to an increased frequency of fires in recent years, resulting in the loss of a thick layer of grass roots on the rocky underground. However, the most imminent threat to the toads’ survival at present is the proposed mining project in the core area of their range. It is thus imperative that the Critically Endangered status of the Nimba toad be retained for the present. However, a broader and more in-depth study of the population sizes, population genetics and the microhabitat needs is urgently needed.