PRIMATE SOCIAL-GROUPS AS BIOLOGICAL ISLANDS

The intestinal protozoan faunas of 11 social groups of Cerocebus albigena, 3 groups of Cercophithecus mitis, 3 groups of C. ascanius, 2 groups of rain forest and 4 groups of savannah Papio anubis are documented. All individuals in a particular social group exhibit identical protozoan faunas. All social groups of each species, except the savannah P. anubis, exhibit intergroup differences in the composition of their protozoan faunas. The number of intestinal protozoan species in C. albigena social groups is a function of group size. The similarity between the protozoan faunas of different C. albigena groups is related to the density of social groups and types of land tenure in particular localities. Past social history of C. albigena groups may have some influence on the level of similarity of different groups'' faunas. Entrance of a nongroup member into a group of C. mitis resulted in an increase in the species richness of the group''s protozoan fauna. Group fission may result in reduction of a group''s protozoan species richness. All groups of savannah P. anubis exhibit identical protozoan faunas. This may be because savannah P. anubis has a higher rate of exchange of individuals between groups than has been recorded for the rain forest primates under consideration. The differing rates of exchange may be due to disease-related selection against traits which result in high rates of individual exchange among rain forest primate groups. Primate social groups are functionally biological islands; the species richness of their protozoan faunas changes according to group size and levels of protozoan migration between groups.