Gorillas, the largest living primates, inhabit the tropical forests of equatorial Africa. These powerful creatures are often perceived as strictly vegetarian. While their primary food source is plant-based, a closer look reveals nuances in their dietary habits.
The Gorilla Diet
Gorillas are primarily herbivorous. Their diet includes leaves, stems, roots, bark, and fruits, with variations depending on the gorilla species and their specific habitat. Mountain gorillas, found in higher altitudes, consume large quantities of fibrous vegetation such as thistles, nettles, and bamboo shoots. Their diet consists of about 86% leaves, shoots, and stems, with only a small percentage of fruit due to its scarcity in their high-altitude environment.
In contrast, western lowland gorillas, inhabiting dense forests, have a more diverse diet that includes a greater proportion of fruit when available. Fruit makes up around 67% of their diet, supplemented by leaves, seeds, and stems. During dry seasons when fruit is scarce, these gorillas adapt by consuming more fibrous plants and tree bark to meet their nutritional needs. An adult male gorilla can consume over 18 kilograms (40 pounds) of vegetation daily to acquire sufficient nutrients from their low-quality plant diet.
Dietary Nuances
While gorillas are overwhelmingly plant-eaters, their diet is not exclusively vegan. They occasionally consume small quantities of animal matter, primarily insects such as termites, ants, grubs, and caterpillars. This constitutes less than 0.1% of their overall food intake. Western lowland gorillas, for instance, have been observed to break open termite nests to eat the larvae.
The consumption of insects is incidental or a supplemental source of certain minerals, not a primary food-seeking behavior. For example, western lowland gorillas may select termites high in iron and ash. Although these minor inclusions mean gorillas are technically omnivores, their diet remains overwhelmingly plant-based, classifying them as primarily herbivores.
Digestive Adaptations
Gorillas possess specialized digestive systems that enable them to thrive on their high-fiber, plant-heavy diet. Mammals lack the enzymes to directly break down cellulose, a tough fiber found in plant cell walls. Gorillas overcome this challenge through a symbiotic relationship with a diverse community of microbes, including bacteria, fungi, and archaea, residing in their large gastrointestinal tracts.
These gut microbes ferment the indigestible plant material, converting cellulose into short-chain fatty acids, which gorillas then absorb as an energy source. Their digestive system, particularly the large colon and cecum, is considerably larger than that of humans, allowing for prolonged fermentation of bulky vegetation. This efficient microbial processing and a long retention time for food in their digestive system help extract enough nutrients from their low-calorie, fibrous diet to support their massive size and energy requirements.