The great apes, which include orangutans, gorillas, bonobos, and chimpanzees, along with the lesser apes (gibbons and siamangs), are primarily herbivorous species. Their diets rely overwhelmingly on plants, consisting mostly of fruits, leaves, and other vegetation, a feeding strategy known as frugivory and folivory. Despite this general rule, some ape species engage in limited consumption of animal protein. This occasional shift from a plant-based diet provides concentrated energy and specific nutrients that are otherwise scarce in their environment, serving both nutritional and complex social functions.
The Great Apes Known for Predation
Among the great apes, the common chimpanzee (\(Pan\) \(troglodytes\)) is recognized as the most frequent and sophisticated predator. Across their range, chimpanzee communities regularly hunt small and medium-sized mammals, a behavior observed at all long-term field sites where prey species are available. Hunting frequency varies significantly by location, but in some well-studied communities, events occur as often as four to ten times per month. These predatory activities are predominantly carried out by adult males, who are responsible for the vast majority of successful kills.
Bonobos (\(Pan\) \(paniscus\)), the chimpanzee’s close relative, also consume meat, often at rates comparable to chimpanzees in certain forest areas. However, the social context of their carnivory differs; bonobo meat consumption involves less organized hunting and is frequently controlled by females. Female bonobos have been documented aggressively maintaining possession of a carcass, sometimes sharing it selectively with subadult males.
The other great apes, gorillas and orangutans, rarely consume vertebrate meat. Gorillas are highly herbivorous, with a diet that can be over 99% plant-based. Their consumption of animal matter is generally limited to small insects and larvae ingested incidentally with their massive quantities of vegetation. Orangutans also maintain a highly frugivorous and folivorous diet, and reports of them consuming vertebrate meat are exceedingly rare, often involving opportunistic scavenging.
Defining Meat: Insects, Scavenging, and Active Hunting
Insectivory
The simplest form of animal protein acquisition is insectivory, the consumption of social insects like termites and ants, which is common across many ape species. Apes frequently use tools, such as modified sticks and grass stems, to extract these insects. This provides a readily available source of protein and mineral salts. This form of animal protein acquisition is widespread and often low-cost.
Scavenging
Scavenging, or consuming an animal that has died from other causes, is a less common but observed behavior. Bonobos, for instance, have been seen feeding on carcasses of small forest antelopes, suggesting opportunistic meat acquisition. While there are anecdotal accounts of gorillas sampling small dead animals, intentional scavenging of large vertebrates is not a defining characteristic of their diet.
Active Predation
Active predation represents the most complex form of meat acquisition, primarily observed in chimpanzees and bonobos. Chimpanzees specialize in hunting small to medium-sized mammals, with non-human primates, particularly red colobus monkeys, being the preferred prey in many regions. These hunts often involve strategic, cooperative tactics, where groups of chimpanzees work together to block escape routes, drive the prey, and ambush it, demonstrating a high level of coordination. Bonobos also engage in active hunting, targeting small forest antelopes like the Weyn’s duiker.
Nutritional and Social Drivers for Carnivory
Meat consumption, while a small percentage of the total diet, is biologically significant because it provides a concentrated package of nutrients. Animal flesh delivers high-quality protein and essential fatty acids that are difficult to obtain efficiently from the typically fibrous, low-nutrient plant foods of the forest. For developing young and reproducing females, this dense source of calories and micronutrients is particularly valuable for growth and reproductive success. Analyses of stable isotopes in chimpanzees confirm that adult males, the primary hunters, consume measurably more vertebrate meat than females, reflecting its importance in their overall metabolic needs.
Meat serves as a form of social currency within chimpanzee and bonobo communities. A successful kill becomes a highly valued resource that the possessor can use to influence social dynamics. Meat sharing is not always a peaceful, altruistic act; it is often a tactical behavior used to reinforce alliances between males, secure support, or even be exchanged for mating opportunities with females.
The act of sharing can solidify the hunter’s status, demonstrating his prowess and reliability to the rest of the group. In chimpanzees, the division of a carcass is frequently competitive, with individuals begging or harassing the possessor for a piece. This social context of competition and exchange means that the value of meat is often as much about maintaining group structure and individual rank as it is about satisfying a biological hunger.