The social and spatial organisation of the beira antelope (Dorcatragus megalotis): a relic from the past?

Abstract

We studied the social and spatial organisation of the beira (Dorcatragus megalotis) in arid low mountains in the South of the Republic of Djibouti. Beira was found to live in socio-spatial units whose ranges were almost non-overlapping, with a surface area of about 0.7 km2. Each unit included a single adult male, and from one to three adult females. On average, the members of a unit made up a single group during 76% of the observation time, 92% outside the periods when a neonate was in the “hider” stage and/or an adult female in oestrus. Collective sequences of linked urination–defecation were frequent. Members of neighbouring units rarely met and interacted, chasing behaviour occurring mainly between adult males. Overall, the social and spatial organisation of the beira appears to be intermediate between that of the dik-diks (Madoqua spp.), in which units exceptionally include more than one adult female, and that of the oribi (Ourebia ourebi), in which units can include several adult males. Moreover, it resembles those of the klipspringer (Oreotragus oreotragus) and rhebok (Pelea capreolus), two morphologically conservative species that do not belong to the tribe Antilopini. We suggest that the beira’s social and spatial organisation might be similar to that of the last common ancestor to the Antilopini, if not to most of the extant Antilopinae.