The question of whether apes are omnivores requires a look at the diverse diets across the Hominoidea superfamily, which includes the great apes: Gorillas, Orangutans, Chimpanzees, and Bonobos. Lesser apes, such as Gibbons, are also part of this group. While all these species share a close evolutionary history, their environments and foraging strategies have led to different dietary profiles. Determining if they are omnivores depends on how much non-plant matter they consume and what role it plays in their overall nutrition.
Defining Dietary Categories
Animals are classified into three primary dietary categories based on their main food source. Herbivores primarily consume plant matter, such as leaves, fruits, stems, and roots. Carnivores exclusively eat meat, hunting and consuming other animals for nutrition. Omnivores consume a diverse diet of both plant-derived and animal-derived food sources. For an animal to be classified as a true omnivore, it must derive significant nutritional energy from both plant and animal sources, demonstrating adapted digestive systems and foraging behavior. This classification is based on what an animal regularly eats for sustenance.
The Predominant Diet of Great Apes
The diets of most great apes are overwhelmingly dominated by plant matter, leading to their classification as herbivores, or more specifically, frugivores (fruit eaters) and folivores (leaf eaters). Orangutans, found in the rainforests of Borneo and Sumatra, are highly frugivorous, often consuming 60 to 90 percent fruit when it is abundant. They supplement this diet with young leaves, bark, and insects, but fruit remains their primary caloric source.
Gorillas, the largest of the primates, are primarily folivores, focusing on foliage and plant stems. Mountain gorillas, for example, consume up to 86 percent leaves, shoots, and stems, with only about two percent of their intake coming from fruit due to the high-altitude environment. Western lowland gorillas consume more fruit, sometimes up to 67 percent of their diet, but green plant material still makes up the majority of their overall food intake. Gibbons also fit this plant-heavy model, with fruit often accounting for 49 to 61 percent of their feeding time.
When Apes Consume Meat: Opportunistic Behavior and Insectivory
The complication in classifying apes arises from their consumption of animal matter, which is a regular, though small, part of their diet. Virtually all ape species engage in insectivory, regularly consuming termites, ants, caterpillars, and other invertebrates. This consumption of insects, while technically animal protein, is often viewed as a micronutrient supplement rather than a significant caloric driver.
Chimpanzees present the most compelling case for a broader dietary classification due to their systematic hunting of vertebrates. They frequently hunt small-to-medium-sized mammals, with Red Colobus monkeys being a preferred and regularly targeted prey. Although meat constitutes less than five percent of a chimpanzee’s total feeding time, the hunting behavior is coordinated, intentional, and observed across all studied populations.
Bonobos, the chimpanzee’s close relative, also consume meat. Recent observations indicate that bonobos, particularly females, capture and eat small antelopes, like duikers, and other small mammals at a frequency similar to some chimpanzee groups. This meat consumption, estimated to be around three percent of their diet, combined with regular insectivory, is best described as faunivory (the consumption of animal protein). While most apes are primarily herbivores, chimpanzees and bonobos exhibit a pattern of opportunistic omnivory because they deliberately and systematically incorporate vertebrate meat into their diet.