The East African oryxes have traditionally been treated as a single species, Oryx beisa (and often even considered conspecific with the Gemsbok, O. gazella, of southwestern Africa). According to Groves (2011), however, although they are very similar in appearance they are best treated as three distinct species: Beisa Oryx (O. beisa), found in northern and central Somalia and the Ogaden region of Ethiopia north to Berbera, west to Eritrea, and south into the Awash Valley; Galla Oryx (O. gallarum), found in northern Kenya and northeastern Uganda and extending into Somalia and southeastern Ethiopia; and Fringe-eared Oryx (O. callotis), found in southeastern Kenya and northeastern Tanzania.
The Beisa Oryx is a large antelope with a thick neck, long face, and long straight horns. It is found mainly in desert country, arid grassland, and scrub. It typically occurs in small herds of 7 to 30 individuals. It is reported to be common in the Awash National Park, but declining elsewhere due to hunting and overgrazing. Population declines likely approached 25% over the past three generations.
(Kingdon 1997; Groves 2011)