The four genera of great apes—gorillas, chimpanzees, bonobos, and orangutans—exhibit a wide range of dietary behaviors that challenge the common assumption that they are purely plant-eaters. While most of their caloric intake comes from plant sources, the inclusion of animal matter, whether opportunistic or actively hunted, provides the definitive answer. Examining the feeding strategies across the great ape family reveals a complex spectrum from near-total herbivory to regular meat consumption.
Largely Herbivorous Apes
Gorillas, the largest great apes, are the species most aligned with the public perception of a plant-based diet. Their massive bodies are supported primarily by a high volume of fibrous vegetation, classifying them as functional herbivores. The bulk of their daily intake consists of leaves, shoots, stems, pith, and bark, with an adult male consuming over 40 pounds daily.
This leafy diet is supplemented seasonally by fruits, particularly among western lowland gorillas, where fruit can constitute up to 67% of their diet when available. Mountain gorillas, by contrast, rely almost entirely on the abundant low-calorie foliage of their high-altitude habitat, consuming minimal fruit.
Gorillas are not strictly vegetarian, however, because they consume small amounts of animal protein, primarily insects. They ingest ants, termites, caterpillars, and grubs, sometimes deliberately to gain trace minerals and protein. This animal matter typically accounts for less than 0.1% of their total diet, confirming that even the most herbivorous ape is not a true vegan.
Apes That Actively Hunt and Consume Meat
The question of ape vegetarianism is decisively answered by the dietary habits of chimpanzees and bonobos, both classified as omnivores. Chimpanzees are known for active and coordinated hunting behaviors targeting small-to-medium-sized mammals. They frequently engage in group hunts, primarily for monkeys, demonstrating a preference for vertebrate meat.
Meat provides a concentrated source of protein and fat, which is highly valued and often becomes a social tool. Meat sharing is a political act, used by males to maintain alliances, secure social status, and gain mating opportunities. Beyond hunting mammals, chimpanzees routinely consume large quantities of insects, including termites and ants, often extracted using tools. Their diet is estimated to contain up to six percent animal matter, confirming their status as regular meat-eaters.
Bonobos share the omnivorous classification but display less frequent and less systematic hunting of mammals. Their diet is primarily frugivorous, meaning fruit is the dominant food source, making up over half of their intake. Despite this preference, bonobos regularly supplement their diet with invertebrates, such as earthworms and termites, and occasionally consume small vertebrates like flying squirrels or duikers. These instances of consuming animal protein cement their non-vegetarian status.
Dietary Opportunism and Regional Variation
The great ape diet is remarkably flexible, driven by environmental availability, which is clearly seen in orangutans. Orangutans are highly dependent on fruit, which can constitute up to 90% of their diet when abundant, leading to their classification as frugivores. The unpredictable nature of rainforest fruiting seasons forces them to be highly opportunistic feeders.
When preferred fruit sources are scarce, orangutans rely on a variety of “fallback foods” to survive. This shift includes consuming significant quantities of leaves, young shoots, tree bark, and roots to maintain energy. This fallback diet also includes animal matter, as they actively forage for insects, honey, and bird eggs. Though rare, they have been observed consuming small vertebrates like slow lorises, ensuring they obtain necessary protein when plant-based options are limited.
This flexibility highlights how geography and seasonality create significant variations in diet across all great ape populations. For example, western lowland gorillas consume far more fruit and insects than their mountain-dwelling counterparts due to habitat differences. The ability of all great apes to switch between a plant-heavy diet and a diet supplemented with animal protein, depending on what their environment provides, confirms that none are true vegetarians.