Subtrooping in a chacma baboon (Papio ursinus) population

Subtrooping in two baboon troops at Suikerbosrand, South Africa, was observed during a study of intertroop relations. Individual associations and locations were opportunistically recorded. Subtrooping varied in frequency according to season, being more frequent in the seasons with lower temperatures and food availability. Some subtroops frequented only certain parts of the larger troop range and remained separate from other groups for up to several days. Comparison with reports of subtrooping in other chacma populations reveals the study population to be relatively unique in the seasonality of subtrooping, the consistency of membership and the frequent occurrence of one-male subtroops. Lack of predation coupled with genetic isolation for several generations may have allowed the Suikerbosrand population to increase the efficiency of resource use in the less favorable seasons of the year, especially for less dominant individuals, through subtrooping. Subtrooping appears to be a facultative potential of all baboon species that requires little genetic change to develop.