Monkeys do engage in intra-species consumption, but it’s not a common dietary practice. While rare, specific circumstances can lead to individuals consuming parts of, or entire, conspecifics. This article explores the forms and underlying reasons for such behaviors in the primate world.
Instances of Intra-Species Consumption
Monkeys engage in intra-species consumption primarily through two distinct behaviors: infanticide followed by consumption and opportunistic scavenging. Infanticide, the killing of infants by adults of the same species, sometimes includes partial or full consumption of the infant’s body.
Male primates, such as Hanuman langurs and chimpanzees, are known to commit infanticide, and on occasion, parts of the deceased infant may be consumed. A review of 40 chimpanzee infanticide cases found that 23% involved complete consumption and 37.5% partial consumption. Cases of infant cannibalism following infanticide have also been reported in New World monkeys, including common marmosets (Callithrix jacchus) and moustached tamarins (Saguinus mystax). A recent observation documented a case in wild white-faced capuchin monkeys, where group members consumed a deceased infant, likely a victim of infanticide.
Scavenging represents another form of intra-species consumption, where monkeys feed on the remains of conspecifics that have died from causes other than direct predation by group members. This often occurs opportunistically, such as when an individual dies due to illness, accident, or predator attack. For example, a female drill was observed consuming her infant’s corpse days after its death, a rare instance of maternal cannibalism.
While chimpanzees sometimes consume infanticide victims, the consumption of conspecific corpses following non-violent death is uncommon for them. This opportunistic feeding on already deceased individuals is distinct from actively hunting and killing a conspecific for food. These behaviors highlight specific contexts for conspecific consumption, rather than a general predatory inclination.
Motivations Behind These Behaviors
The motivations driving intra-species consumption in primates are diverse, often linked to reproductive strategies, resource availability, or extreme environmental pressures. Male infanticide is frequently explained by the sexual selection hypothesis. Male primates kill unrelated infants to shorten the mother’s lactational amenorrhea, accelerating her return to reproductive receptivity and increasing reproductive success. Consumption in these instances may be an opportunistic byproduct or a way to gain nutrients.
Resource competition can also motivate infanticide, especially in high-population density areas or during food shortages. Eliminating younger, dependent individuals reduces the overall demand for limited resources. Less common instances of maternal infanticide and consumption link to the mother assessing low chances of infant survival, potentially conserving resources for future reproductive attempts.
Scavenging on deceased conspecifics is primarily driven by nutritional needs. In environments with scarce food sources, consuming available remains provides energy and nutrients. This is often an act of desperation, not a primary food source. Extreme starvation or environmental stress can lead to conspecific consumption beyond typical infanticide or scavenging, indicating a survival mechanism in dire circumstances.
The Infrequency of True Cannibalism
Despite these documented instances of intra-species consumption, true predatory cannibalism—where a primate actively hunts and kills another for food—is remarkably rare among monkeys. Behaviors like infanticide with consumption or scavenging are typically opportunistic and context-specific, differing significantly from a deliberate hunting strategy.
Several factors contribute to the rarity of predatory cannibalism in primates. Engaging in such behavior carries high social costs, potentially leading to aggression from other group members or exclusion. There is also a significant risk of injury during a confrontation with a healthy conspecific. Furthermore, consuming individuals from the same species increases the risk of disease transmission, particularly for pathogens like prions, which caused Kuru in humans through ritualistic consumption.
While primates do consume meat from other species, their typical diets are diverse, often consisting of plants, fruits, and insects, which meet their nutritional requirements. The overall evidence suggests that while monkeys may consume parts of conspecifics under specific circumstances, predatory cannibalism is not a common or adaptive strategy. These rare occurrences are generally driven by unique ecological or social pressures, rather than being a routine part of their diet or behavior.