Currently the size of primate groups is believed to be determined by the density and distribution of food resources. However, this model rests on a number of assumptions, and there are reasons to question the widespread acceptance of these assumptions. For example, the model assumes that as group size increases, animals will have to travel further to find food. However, studies of leaf-eating monkeys find no such relationship. The model also assumes that food resources are clumped, however some primates rely on resources that are quite dispersed. It is unclear how this group size model, as presently developed, would apply to either of these situations. We will conduct a 3-year study in Kibale National Park, Uganda to examine what determines the size of primate groups in three species that differ in their foraging strategies. Based on previous three species of monkeys have been selected for study; one species for which the assumptions of the model are probably upheld (mangabeys - Cercocebus albigena) and two species for which the assumptions are violated (red colobus - Colobus badius rely on leaf resources which have been suggested to be non-depleting; and redtail monkeys - Cercopithecus ascanius rely on dispersed foods).
