The BMNP encompasses a broad range of habitats between 1,500 and 4,377 m altitude. These provide a large number of niches for animals, and as a result there is great variety in the fauna. Much of the original stimulus for making a National Park in the Bale Mountains was the plights of the endemic Mountain Nyala and the Ethiopian wolf. There are, in fact, at least 46 mammal species, and 160 bird species, in addition to the numbers of species from other animal orders-reptiles, amphibians etc., that all have a part in the complex ecosystems that have evolved in this unusual area.
A large proportion of the Bale Mountains fauna is endemic- found nowhere else in the world, and in some cases nowhere else in Ethiopia. The variety of species and high rate of endemicity is due to the wide variety of habitats conserved in BMNP and to the isolation of the highland areas of Ethiopia from other similar highlands in Eastern Africa, by the surrounding hot dry lands. Ethiopia as a whole has a large number of endemic species.

Yalden (1983) calculated that almost 80% of the land in Africa over 3,000 m altitude occurs in Ethiopia, and speculated that the high rate of endemicity was a result of this very large area of highland.

It is certain that the numbers of endemic species in the invertebrates, and in the flora, will also prove to be very high in Bale. Information from a number of sources, but mainly from the works of Largen and Yalden, underlines the importance of the Bale Mountains as a center of endemicity, and reserve of unknown genetic resources, (Hillman,1986).

The three main sub-sections of the park Northern Gaysay area, Central peaks and Sannetti plateau area and Southern Harenna area are demarcated by altitude, and this also controls vegetation zonation. Thus the central peaks and plateau area consists of Afroalpine vegetation; the northern Gaysay area of grassland, swamp and woodlands; and the southern Harenna area of dense forest.