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From Primate info net:Geladas are found only in Ethiopia, on the Ethiopian plateau predominantly south of the Tacazze River, north of the Awash River, and east of the Blue Nile River (Dunbar 1993a; Oates 1996). However, a population was found a significant distance from other populations further south along the upper Wabi-Shebeli River, in the Arusi Region (Mori & Belay 1990). In many places, the distribution is discontinuous and the species occurs only very near cliffs and gorges (Dunbar 1993a). Between subspecies, T. g. obscurus is found in the south of the species range, while T. g. gelada is found in the north. They are roughly divided by the gorges of the Belegas and upper Tacazze rivers (Yalden et al. 1977).

The total wild population of gelada baboons is estimated at slightly less than 250,000 individuals (Dunbar 1998).

Afar region

From Wiki:The gelada (Theropithecus gelada), sometimes called the gelada baboon, is a species of Old World monkey found only in the Ethiopian Highlands, with large populations in the Semien Mountains. Theropithecus is derived from the Greek root words for "beast-ape."[3][4] Like its close relatives the baboons (genus Papio), it is largely terrestrial, spending much of its time foraging in grasslands.