the leeward northern ones which are affected by dry Harmattan wind from the Sahara. The Nimba Range, as well as the reserve has exceptional microclimatic diversity. Ecology Mount Nimba Strict Nature Reserve lies within the Guinean Forests of West Africa Biodiversity Hotspot. It harbours an especially rich flora and fauna, and it is the home of more than 2000 vascular plant species, 317 vertebrate species, 107 of which are mammals, and to more than 2,500 invertebrate species. The reserve is a subject of biological surveys, because there are still large numbers of unknown species. Vertebrates endemic to the reserve include the Nimba viviparous toad (Nimbaphrynoides occidentalis), Lamotte's roundleaf bat (Hipposideros lamottei), and Nimba otter shrew (Micropotamogale lamottei). Other rare and endangered animals foudn within the reserve include the West African lion (Panthera leo senegalensis), pygmy hippopotamus (Choeropsis liberiensis), zebra duiker (Cephalophus zebra), and a population of western chimpanzee (Pan troglodytes verus) that use stones for tools. Terrestrial ecoregions within the reserve include Western Guinean lowland forest, Guinean montane forest, Guinean forest-savanna mosaic, and West Sudanian savanna. The Nimba Range is a part of a distinct freshwater ecoregion with a high portion of endemic aquatic species. Terrestrial vegetation varies with altitude and cardinal orientation. The mountain is isolated from other sky islands of Forest Guinea by the lowland West Sudanian savanna and Guinean forest-savannah mosaic. Savanna habitats are broken by gallery forests and closed canopy forest islands. The lowland foothills are covered by the Western Guinean Lowland Forest up to 600 meters. The characteristic forest type is semi-deciduous high forest with a main canopy and an emergent layer. There are 40-70 tree species found in a single hectare, and up to 500 forest tree species recorded in the area. Guinean Montane Forests are located between 600 and 1200–1400 meters. At lower levels, semi-deciduous high forests extend up to 900 meters; they are poorer in species compared to lowlands. Short dry forests can be found in the eastern end of the ridge. From 900 meters altitude, where the mountain is covered by clouds almost most of the year, mossy forests are present, which can be divided into three types: Parinari exclesa forests (1), summit forests (2), and tree fern forests in the valleys where ground water is abundant (3). Above the tree zone, there is a transition of Protea bushland to grassland. Isolated high-altitude grassland extends from 1200 to 1400 meters to