Chimpanzees (Pan troglodytes) are highly intelligent, socially complex primates that share a close evolutionary relationship with humans. They inhabit diverse environments across Africa, exhibiting sophisticated behaviors like tool use and cooperative hunting. As omnivores, their diet primarily consists of fruit, leaves, insects, and meat. While not a routine dietary practice, cannibalism (the consumption of conspecifics) is a documented behavior in wild chimpanzee populations, occurring infrequently within specific social or ecological contexts.
Infanticide and Reproductive Strategy
The most intensely studied context for chimpanzee cannibalism is linked to infanticide perpetrated by adult males within their own community. This behavior is understood through the sexual selection hypothesis, which posits that the aggression serves a reproductive advantage. By killing an unweaned infant that is not his own, a male removes the nursing constraint on the mother. This action hastens the female’s return to estrus, enabling the male to mate with her and potentially sire her next offspring sooner.
Studies found that females who lost an infant to infanticide conceived on average about seven times more quickly than if their infant had survived. The victims of these attacks are disproportionately young; two-thirds of victims in one study were less than one week old. Cannibalism often follows the violent killing, but it is typically partial and infrequent. This suggests that meat acquisition is a secondary by-product of the aggressive reproductive strategy, and the motivation is rooted in reproductive competition rather than simple hunger.
Opportunistic Consumption of Deceased Group Members
A non-aggressive form of consumption occurs opportunistically when group members encounter an individual who is already deceased. This context involves the consumption of stillborn infants or those who died shortly after birth due to natural causes. These instances are distinct from aggressive infanticide because the individual was not killed for a social or reproductive gain. The motivation is often viewed as a response to the presence of a deceased body, sometimes involving resource utilization.
Mothers may exhibit complex behaviors toward their deceased offspring, often carrying the corpse for days or weeks before abandoning it. While the mother may groom and protect the body, rare cases of partial consumption have been reported by the mother or close relatives. In groups where hunting is infrequent, individuals may be less likely to perceive the deceased as a food source. This suggests a link between general predatory behavior and the likelihood of opportunistic consumption.
Consumption During Inter-Group Conflict
Cannibalism also surfaces in the context of lethal inter-group conflict, an extension of chimpanzee territoriality. When males conduct border patrols and encounter rivals, these clashes can result in fatal attacks on juveniles or adults. The resulting consumption of the defeated individual’s remains is linked to maintaining dominance and expanding territory.
During these lethal encounters, victorious chimpanzees have been observed to partially consume the bodies of their rivals, including juveniles and adult males. This behavior was documented during the years of conflict at Gombe National Park, where groups fought over territorial gains. The consumption of the enemy is a rare but powerful act that reinforces territorial boundaries and the dominance of the attacking community.