The Nimba viviparous toad, Nimbaphrynoïdes occidentalis, is the only frog or toad on earth to give birth to live young, which are directly nourished by the female during gestation. It has the unique adaptation of its young developing in the uterus of the mother, who hibernates in crevasses in the Nimba Mountains’ rocky, highest elevations during the harsh dry season from November through March. When the rains return, females emerge in April to May and eventually, after 9 months, give birth to live young.
The critically endangered Nimba viviparous toad’s primary habitat is restricted to less than 5 square kilometres of high-altitude grasslands in the Guinean and Ivoirian Nimba Mountains, in disjunct patches. A separate, small population of the toad is known from Liberia, classified as a distinct subspecies N. occidentalis liberiensis.
SMFG has a longstanding partnership with the Museum für Naturkunde of Berlin – the Berlin Museum of Natural History, see https://www.museumfuernaturkunde.berlin/en/science/nimba-project – to study and recommend how to ensure the protection and, if possible, the increase of the Nimba viviparous toad’s population. Every year since 2007, SMFG has supported teams of Guinean and German researchers to survey the toad according to standardised methods. As of early 2020, this had resulted in continuous 13-year dataset from which it is possible to get indications of trends in populations, and to correlate these trends with changes in the toads’ environment such as presence or absence of fire in the dry season, or exploration-related disturbance like drilling.
With support from SMFG, the Museum für Naturkunde has conducted genetic analyses to understand the toad’s genetic diversity across its high-altitude range. It has studied temperature and humidity across the toad’s range, the conditions outside its range in similar-altitude grasslands, and tested which microclimatic conditions the species needs and favours. During the dry season, the Museum’s scientists have searched for the hibernating habits of the Nimba toad.
The Museum für Naturkunde‘s studies have made significant contributions to understanding this unique species. Furthermore, they have informed the design of SMFG’s proposed mining project. Most importantly, because one of the Nimba viviparous toad’s three large populations lives on Signal Sempéré, which is inside SMFG’s Mining Concession, the company has permanently removed this from the mine plan as a ‘set-aside’. Signal Sempéré will be used only for research and conservation; no new infrastructure will be installed there.
Using the results of this research, SMFG and the Museum für Naturkunde will work with the Nimba protected area authority and other partners to manage the mountains’ high-elevation grasslands in manners that enhance its suitability for the toad. This could include managing wild fires to reduce their impact, encouraging certain native vegetation types, or simply minimising disturbance in the core of their range.