Chimpanzees-red colobus monkeys: A predator-prey system

The arms race between a predator and its prey may lead to different outcomes in different environments. To follow such 'coevolution' between chimpanzees, Pan troglodytes, and red colobus monkeys, Colobus badius, populations of both species living in the Gombe Stream National Park, Tanzania, and in the Taï National Park, Côte d'Ivoire, were compared. Humans have a much stronger impact on hunting in Gombe than in the Taï forest and when this is accounted for, Taï chimpanzees hunt more frequently than Gombe chimpanzees. After excluding this human effect, Gombe colobus monkeys are more aggressive towards chimpanzees than Taï colobus monkeys, which might explain why Gombe chimpanzees are more afraid of the colobus than Taï chimpanzees. The initial factor that might have led to these differences is the lower height of trees in the woodland of Tanzania than in the tropical rainforest of Côte d'Ivoire. A dynamic arms race is in progress between the two species in both sites. In one case Gombe chimpanzees initiated a new strategy that was followed by a counter-response from the red colobus monkeys. A scheme is proposed that could account for the evolution between the two species from the aggressive colobus and fearful chimpanzees in Gombe to the more wary colobus and confident chimpanzees in the Taï forest. © 1994 The Association for the Study of Animal Behaviour.