Gorillas, the largest primates on Earth, are powerful animals whose immense size belies their predominantly plant-based diet. These forest dwellers are herbivores, relying almost entirely on vegetation for sustenance.
Primary Food Sources
The majority of a gorilla’s diet consists of various plant parts, including leaves, stems, and shoots like bamboo. For mountain gorillas, approximately 85% to 86% of their diet is composed of these fibrous green materials. They often prefer younger leaves, which contain less fiber and more protein, providing better nutritional value.
Fruits represent another important food source, particularly for lowland gorilla species. Western lowland gorillas, for example, consume a high percentage of fruit, which can make up to 67% of their diet. Gorillas climb trees to harvest ripe fruits, using their keen sense of smell to locate them. The availability of fruit often depends on the season, influencing their foraging patterns.
Bark and roots serve as supplementary food items, especially when preferred options like fruits are scarce, such as during dry seasons. Gorillas gnaw or peel bark from trees, and this provides essential minerals like sodium. Roots and pith, the soft inner core of plants, are also consumed, offering nutrients and moisture.
Gorillas occasionally consume small quantities of insects, primarily termites and ants, which provide additional protein and minerals. This animal matter typically constitutes a very small fraction, often less than 0.1% to 3%, of their overall food intake. They may also ingest flowers, seeds, and small amounts of soil, which can supply missing minerals or help neutralize plant toxins.
Dietary Variations and Foraging Habits
The specific diet of a gorilla can vary significantly based on its species and the unique characteristics of its habitat. Mountain gorillas, residing in high-altitude environments, have limited access to fruits, so their diet is largely dominated by leaves, stems, and shoots. They may consume a narrower range of plant species compared to their lowland relatives, such as only 38 different plant species in the Virunga Volcanoes.
Conversely, western lowland gorillas inhabit forests where fruits are more abundant, leading to a broader diet of up to 200 different plant species. During periods of fruit scarcity, lowland gorillas adapt by increasing their consumption of more fibrous plants and tree bark. This adaptability helps them sustain themselves despite seasonal changes in food availability.
Gorillas spend a substantial portion of their day foraging and eating, often dedicating about half of their waking hours to these activities. They are nomadic within their home ranges, moving daily to find fresh food sources and prevent overexploitation of any single area. Their foraging is selective, as they choose specific parts of plants, such as young leaves, pith, or roots, based on their nutritional content.
An adult male gorilla can consume a remarkable 18 to 30 kilograms (approximately 40 to 66 pounds) of vegetation daily, while females typically eat slightly less. Gorillas possess immense strength and dexterity, which they use to tear apart vegetation or access internal plant parts like the pith of a banana tree. They rarely need to drink water directly from standing sources, as the succulent nature of their plant-based diet, along with morning dew, provides most of the hydration they require.