Gorillas are the largest primates on Earth, ground-dwelling apes that inhabit the forests of Central Africa. These powerful animals belong to the genus Gorilla, which includes two species and four subspecies, all of which are strictly herbivorous. While their diet is plant-based, the specific food items and nutritional focus vary significantly based on the subspecies and the altitudinal zone of their habitat. The local availability of vegetation and fruit dictates a specialized approach to foraging, leading to distinct dietary profiles across different populations.
The Herbivorous Diet of Mountain Gorillas
Mountain gorillas (Gorilla beringei beringei) live in high-altitude montane and bamboo forests where fruit is scarce, leading to a diet heavily focused on bulk vegetation. Their food consists of approximately 86% leaves, shoots, and stems, with roots and rhizomes accounting for another 7% of their intake. This high-fiber, low-sugar diet requires them to consume vast quantities of plant material; an adult male can ingest over 18 kilograms of vegetation daily to meet energy needs.
The high-altitude habitat limits fruit availability, which makes up only about 2% of their diet and is consumed opportunistically. They rely on plants like wild celery, thistles, and nettles, often stripping the outer layers to access the softer pith and stalk. This strategy allows them to process large volumes of fibrous matter. They have been documented to feed on parts from over 140 different plant species.
Roots, bark, and flowers also form minor parts of the mountain gorilla’s intake. Although primarily herbivores, they occasionally consume small invertebrates, such as ants, snails, and grubs, which provide a trace amount of protein, making up about 2% of their diet. Since their main food sources (leaves and stems) are available year-round, they do not require significant seasonal dietary shifts.
The Diverse Frugivorous Diet of Western Lowland Gorillas
The diet of the Western Lowland Gorilla (Gorilla gorilla gorilla), which inhabits equatorial rainforests, differs significantly from their mountain relatives due to the abundance of seasonal fruit. Fruit can constitute a large portion of their diet, sometimes reaching up to 67% of their food intake during periods of high availability. This reliance on fruit means their diet is more varied and fluctuates dramatically with the seasons.
When fruit is plentiful, the gorillas travel longer distances to access preferred fruiting trees, acting as effective seed dispersers. They consume parts of nearly 100 plant species, including leaves, seeds, and stems, which become dominant in their diet when fruit is scarce. During dry seasons, they shift to fallback foods like bark, the pith of woody plants, and fibrous terrestrial herbs.
A feature of the Western Lowland Gorilla diet is the consumption of invertebrates, which provides an important source of protein. Termites and caterpillars are regularly sought out, accounting for about 3% of their intake. They often use tools, such as small sticks, to access insects, a foraging technique less common in other gorilla subspecies. This dietary complexity reflects the nutritional richness available in the lowland forest environment.
Foraging Behavior and Hydration
Gorillas spend between four and six hours daily actively foraging for food. They are selective eaters, often consuming only specific parts of a plant, such as tender shoots, inner pith, or the base of a leaf. They use their hands and lips to manipulate vegetation, stripping leaves from stems or peeling bark to access the softer layer beneath.
They move through their environment, cropping vegetation in a way that allows for rapid regrowth, ensuring the sustainability of their food sources. The dominant silverback determines the daily foraging routes, leading the group to known patches of high-quality food. Their size and strength are used to break apart large, tough vegetation, such as shredding a banana plant to reach the central pith.
Gorillas rarely drink standing water, a behavior partly attributed to their fear of water bodies. They obtain almost all necessary hydration from the vegetation they consume, which can contain up to 50% water content in succulent plants. They also rely on morning dew that collects on the leaves they eat. In response to higher temperatures, gorillas have been observed to obtain water by using the hair on the back of their hands to soak up moisture.