Infanticide and social organization in the redtail monkey (Cercopithecus ascanius schmidti) in the Kibale Forest, Uganda.

The redtail monkeys of the Kibale Forest, W. Uganda, live in social groups of about 35 members with only one adult male. In one of the study groups the harem male was replaced by a new male from outside the group. This male-replacement was followed by the new male killing and eating two newborn infants in the group. Infants and young juveniles older than one month were not attacked. Following the infanticide the new male copulated with several adult females in the group. 8 months after this male joined the group, 5 other adult and subadult males associated with it. This multimale influx was accompanied by frequent and intense aggression among the males. Comparisons are made with the studies of langurs in India and Ceylon and it is suggested that infanticide following male-replacement in the harem affords reproductive advantages to the new male.