Monkeys, like many animals, exhibit behaviors that can seem unsettling to human observers, and the consumption of conspecifics—members of their own species—is one such phenomenon. While not a typical dietary staple, instances of conspecific consumption do occur in specific circumstances among primates. This behavior challenges common perceptions of animal conduct, prompting closer examination of its forms and underlying reasons. Understanding these instances provides insights into primate social structures, reproductive strategies, and survival mechanisms.
Understanding Conspecific Consumption in Primates
The term “cannibalism” in primates encompasses several distinct behaviors, not just active predation. One common form is infanticide followed by consumption, where an adult primate kills an infant of its own species and then eats part or all of it. This often relates to reproductive strategies, particularly among males seeking to accelerate a female’s return to fertility.
Another type involves scavenging on deceased conspecifics, meaning individuals feed opportunistically on those who have died from other causes like illness, injury, or predation. This is not active killing but rather utilizing an available food source. Direct predation on adult conspecifics for sustenance is exceedingly rare, typically occurring only under extreme environmental conditions.
Documented Cases in Monkey Species
Observations of infanticide followed by consumption have been documented across various primate species. Hanuman langurs, for instance, are well-known for male infanticide, where new dominant males kill infants sired by previous leaders, sometimes consuming the victims. Similarly, baboons, including chacma and olive baboons, exhibit infanticide, with some instances involving consumption of the infant. Chimpanzees, though apes, have also been observed committing infanticide and partially consuming victims, often in intercommunity conflicts.
Scavenging on deceased conspecifics also occurs. A rare case involved white-faced capuchin monkeys consuming a 10-day-old infant that had fallen to its death, though most group members only inspected the corpse. Mothers of various primate species, including baboons, orangutans, Japanese macaques, and rhesus macaques, have been observed carrying their dead infants for days and, in some cases, consuming parts of the mummified remains. A drill monkey mother was also observed consuming her deceased infant in a captive setting.
Why This Behavior Occurs
Several factors contribute to conspecific consumption in primates. Infanticide, particularly by males, is often a reproductive strategy. Males who take over a new group may kill unweaned infants, causing females to cease lactation and return to estrus sooner, thereby accelerating the male’s opportunity to sire his own offspring. This behavior increases the male’s reproductive success within his limited tenure as a dominant male.
Resource scarcity and nutritional stress can also drive conspecific consumption. When food is extremely scarce, the nutritional benefits from consuming a conspecific, even an infant, can become a desperate measure for survival. Some instances of consumption are purely opportunistic, such as scavenging on individuals who died from non-violent causes, providing an available protein source without the energy expenditure or risk of active hunting. Social pathology, stemming from overcrowded or stressful environments, may also contribute to such behaviors. These factors highlight the adaptive and sometimes desperate circumstances that lead to conspecific consumption in primate populations.