Behavioral Observations on Oryx Antelope (Oryx beisa) Invading Serengeti National Park, Tanzania

In 1959 a boundary change in the Serengeti National Park excluded the area inhabited by oryx antelope. During the following years, only a few solitary animals came temporarily into the park. Beginning in 1972, oryx invaded the southeastern part of the park more frequently and in larger numbers. Recent observations (1974–1975) show that oryx are still only visitors to the Serengeti National Park, but there are indications that they may become resident in the future. Compared with a resident oryx population in the Tarangire National Park, the wandering herds in Serengeti were characterized by (a) a more frequent occurrence of mixed herds of some size, (b) the absence of subadults and juveniles, and (c) the absence of female groups. Small all-male groups, “harem” groups, and solitary adult bulls were recorded in both areas. Oryx exhibit a polyphasic rhythm of daily activity. Except when large concentrations of wildebeest arrive in an area, oryx do not avoid the company of other game species, although they hardly interact with them. A hierarchical organization was recognizable in all the groups observed. Generally bulls ranked over cows, but sometimes subadult or young-adult bulls were dominated by high-ranking cows. Fights among bulls were quite frequent. In addition to spontaneous sparring matches, these agonistic interactions were linked with coordination of group activities, with frontal approaches of group members at close range, particularly in grazing, and with strange bulls joining a herd. The severest fight observed took place between the alpha-bull of a mixed herd and a solitary bull. Peers challenge each other by equivalent, reciprocal displays until fighting develops. In an encounter of unequal opponents, only the dominant animal shows dominance and/or offensive threat displays. The subordinate responds by defensive threats and/or submissive displays. Such a “dominance encounter” ends with the withdrawal of the subordinate without a fight. An alpha-bull of a mixed herd does not fight the subordinate bulls, but frequently has “dominance encounters” with them. In this way, the alpha-bull reinforces his dominance over the others, affects changes in the activity of the group, influences speed, length, and direction of movements, and prevents members of the group, including subordinate bulls, from leaving.