Infanticide in chimpanzees: Review of cases and a new within-group observation from the Kanyawara study group in Kibale National Park

A prolonged attack on a mother and 2-year-old infant that resulted in the d eath of the infant was observed in the Kanyawara study group in Kibale Nati onal Park. The mother was a border-area resident who was first observed ass ociating with unit-group males six years previously. The attackers were an adult male and an adult female with a 6-week-old infant clinging ventrally to her. The attack was unusual in several respects: it is the first time a male and a female chimpanzee have been observed cooperating closely in an i nfanticidal attack; the adult female initially attempted to intervene in th e victim's behalf, but later joined in the attack after receiving aggressio n from the male; and the episode was longer in duration than other reported cases. In the year following the incident, the mother did not increase her association with community males, but was seen with the male who killed he r infant. The relevance of these observations to sexual selection-based exp lanations for infanticide in chimpanzees is discussed.