Gorillas are predominantly herbivorous, meaning their diet largely consists of plant matter. While their immense strength might suggest a diet rich in animal protein, these powerful primates thrive on vegetation. However, their diet is not strictly vegetarian, as they occasionally consume non-plant items.
The Core Plant-Based Diet
The vast majority of a gorilla’s diet consists of various plant parts, including leaves, stems, shoots, bark, roots, and fruits. Mountain gorillas, for instance, are primarily folivores, with leaves making up about 68% of their intake and stems around 25%. This plant-based diet provides the necessary nutrients and bulk to sustain their large bodies.
Gorillas are selective eaters, adapting their intake based on seasonal availability. They prefer young, tender leaves over mature ones due to their lower fiber and higher protein content. The abundance of vegetation allows them to meet high caloric demands by consuming large quantities, sometimes up to 40 pounds (18 kilograms) per day for an adult male.
Beyond Plants: Occasional Inclusions
While gorillas are largely herbivorous, their diet is not exclusively plant-based. They opportunistically consume small quantities of non-plant items, primarily insects. These inclusions, such as termites, ants, and their larvae, contribute trace amounts of high-quality protein and essential amino acids.
The consumption of these invertebrates is minimal, typically contributing less than 0.1% to 2% of their total food intake. Western lowland gorillas, for example, break open termite nests for these protein sources. Some gorillas also ingest soil, which may provide minerals or help neutralize plant toxins.
Regional and Species-Specific Dietary Differences
A gorilla’s diet varies considerably depending on its species and geographical location. This flexibility allows them to adapt to available resources. Mountain gorillas, found in high-altitude montane forests, primarily consume herbaceous vegetation like leaves, shoots, stems, and bamboo. Fruits make up a very small percentage due to limited availability.
Western lowland gorillas, in tropical rainforests, incorporate a higher proportion of fruit when available, sometimes as much as 67% of their diet, supplemented by leaves, seeds, and stems. During dry seasons or when fruit is scarce, they rely more on fibrous plants, bark, and pith, demonstrating adaptability to seasonal shifts.
Nutritional Adaptations
Gorillas possess several biological adaptations enabling them to thrive on their predominantly plant-based diet. Their robust jaws and large, flat molars are well-suited for grinding tough, fibrous plant material. Powerful chewing muscles, anchored by a bony sagittal crest on their skull (especially prominent in males), allow for extensive mastication.
Their digestive system is uniquely adapted to process large quantities of low-calorie, high-fiber vegetation. Gorillas have an elongated intestinal tract, including an enlarged cecum and a large colon, where microbial fermentation of cellulose occurs. This hindgut fermentation, facilitated by gut bacteria, breaks down complex carbohydrates and extracts otherwise unavailable nutrients. This efficient process allows them to obtain sufficient energy and protein from plants to support their massive body size and muscular build.