The oribi is diurnal ( active mainly during the day ) , though some activity may also be observed at night . The animal rest in cover during rain events . Unlike all other small antelopes , oribi can exhibit three types of mating systems , depending on the habitat – polyandry , polygyny and polygynandry ; polygyny tend to prevail as the female @-@ to @-@ male ratio increases . A study suggested that polygyny is preferred in areas of high predator risk , as it lead to formation of groups as an anti @-@ predator measure . Small herds of up to four members are also common .