ANTI-PREDATION BEHAVIOR OF RED COLOBUS MONKEYS IN THE PRESENCE OF CHIMPANZEES

Predator-prey interactions are usually regarded as evolutionary ''arms races'', but evidence is still scarce. We examined whether the anti-p redation strategies of red colobus monkeys (Procolobus badius) are ada pted to the hunting strategies of chimpanzees (Pan troglodytes) in the Tai National Park, Ivory Coast. Tdi chimpanzees search for red colobu s groups, approach them silently and hunt co-operatively. Our playback experiments and observations of natural encounters revealed that red colobus hid higher up the trees in positions where exposure to the for est floor is minimal and became silent, when chimpanzees were close. T hey moved away silently through the canopy, when chimpanzees were stil l at some distance. However, if a group of diana monkeys was nearby in the latter situation, red colobus sought their presence even if they had to move towards the chimpanzees. Chimpanzees refrained from huntin g associated red colobus groups, probably because diana monkeys are ex cellent sentinels for predators approaching over the forest floor. Thu s several elements of both the predator's and the prey's strategies co rrespond to each other. Finally, we compared the interactions between the two species in Tai and in Gombe, Tanzania. We suggest that the dif ference in size ratio between the two species at the two sites and ada ptation of hunting techniques and of escape modes to different forest structures can explain why Gombe red colobus attack chimpanzees while Tai red colobus try to escape. We conclude that predator-prey interact ions can indeed lead to evolutionary arms races, with the specific for m of co-adaptations depending on environmental factors.