Gorillas, the largest living primates, are primarily associated with a strictly vegetarian diet. While their imposing size might suggest varied consumption, their feeding habits are overwhelmingly focused on vegetation. Examining their foraging behavior reveals a nuanced picture, moving beyond the simple label of “herbivore” to explore the minor role non-plant items play.
The Primary Herbivorous Diet
The majority of a gorilla’s daily food intake consists of fibrous plant matter, reflecting their adaptation to the dense vegetation of African forests. An adult male gorilla can consume up to 40 pounds of food daily to sustain its large body mass. Their digestive system is specialized for processing large quantities of leaves, stems, shoots, and pith, which form the dietary backbone year-round.
Staple plant foods vary by region, but often include the leaves and stems of herbs and vines. Young leaves are preferred over mature ones because they contain less fiber and more protein. Lowland gorillas incorporate significant amounts of fruit when seasonally available, while mountain gorillas rely heavily on tough, year-round resources like bamboo shoots, thistles, and nettles. This high-volume, plant-based diet provides necessary carbohydrates and fiber.
Non-Plant Consumption
Gorillas do consume non-plant matter, but this intake is limited almost exclusively to invertebrates, primarily insects. They are not predators of vertebrate animals, and the consumption of true “meat” is not a natural component of their diet. This minor animal consumption, typically less than 1% of their total food intake, serves as an opportunistic source of high-quality nutrients.
Their non-plant targets are often social insects like termites and ants, along with their larvae. Western lowland gorillas have been observed intentionally breaking open termite nests to access the insects, suggesting a purposeful strategy for obtaining protein. Scientific analysis indicates these insect meals provide essential amino acids and minerals, such as iron, that are harder to obtain from high-fiber vegetation. This intentional foraging helps balance the nutritional composition of their predominantly herbivorous diet.
Diet Variation Across Gorilla Subspecies
The exact composition of a gorilla’s diet, including invertebrate intake, is influenced by its subspecies and habitat.
Mountain Gorillas
Mountain gorillas, found in high-altitude montane forests, have the most strictly herbivorous diet. Insects make up a negligible portion, often less than 1–2% of their total food. The cooler climate and higher elevation mean fewer insects are available, and their diet is dominated by leaves, shoots, and stems, sometimes consisting of over 85% foliage.
Western Lowland Gorillas
In contrast, Western Lowland Gorillas inhabit dense, lowland tropical rainforests and exhibit a more varied diet that includes a higher proportion of invertebrates. Insect-eating is more frequent and diverse for this subspecies. These lowland groups also consume a much higher percentage of fruit, sometimes accounting for up to 67% of their diet during peak season, compared to the minimal fruit consumption of mountain gorillas. This difference highlights how ecological factors like fruit and insect availability dictate specific foraging strategies.