THE FORMATION OF RED COLOBUS-DIANA MONKEY ASSOCIATIONS UNDER PREDATION PRESSURE FROM CHIMPANZEES

It is generally assumed that most primates live in monospecific or pol yspecific groups because group living provides protection against pred ation, but hard evidence is scarce. We tested the antipredation hypoth esis with observational and experimental data on mixed-species groups of red colobus (Procolobus badius) and diana monkeys (Cercopithecus di ana) in the Tai National Park, Ivory Coast. Red colobus, but not diana monkeys, are frequently killed by cooperatively hunting chimpanzees. Association rates peaked during the chimpanzees' hunting season, as a result of changes in the behaviour of the red colobus. In addition, pl aybacks of recordings of chimpanzee sounds induced the formation of ne w associations and extended the duration of existing associations. No such effects were observed in reaction to control experiments and play backs of leopard recordings.