 Typically diurnal , the oribi is active mainly during the day . Small herds of up to four members are common ; males defend their group 's territory , 25 – 100 hectares ( 62 – 247 acres ) large . The oribi is primarily a <unk> , and prefers fresh grasses and <unk> occasionally . A seasonal breeder , the time when mating occurs varies geographically . Unlike all other small antelopes , oribi can exhibit three types of mating systems , depending on the habitat – <unk> , polygyny and <unk> . Gestation lasts for six to seven months , following which a single calf is born ; births peak from November to December in southern Africa . <unk> takes place at four to five months . 
