The composition of the gorilla’s diet varies by sub species and seasonality. The western lowland gorillas: the sub species consumes parts of at least 97 plant species. About 67% of their diet is fruits, 17% is leaves, seeds and stems and 3% is termites and the caterpillars. The Eastern lowland gorilla consumes parts of at least 104 plant species. The mountain gorillas eat 142 plant species and only 3 types of fruit. About 86% of their diet is leaves, shoots and stems, 7 % is roots, 3 % is flowers, 2% is fruits and 2 % ants, snails and grubs. The cross river gorillas are not well studied as other sub species. However their diet has been studied through their fecal matter and is known to include fruits, leaves, stems, piths and some invertebrates.
The western lowland gorillas eat a variety of vegetation. The gorillas are able to survive on vegetation like the leaves, stems, roots, vines, herbs, trees and grasses but such vegetation has relatively low nutritional quality. Therefore, they must consume a larger quantity, buts its available all year round.
About the food intake; the adult male gorilla consumes more than 18kg of vegetation per day. The gorillas rarely drink water in the wild because they eat succulent vegetation that is comprised of almost half water as well as morning dew.
The gorillas use their strength to break apart the vegetation. The adult male for example can shred part a whole banana tree to get to the interior tender pith. The gorillas are very selective foragers, they usually eat parts of vegetation, and they eat only leaves, pith, stalk or the roots of a particular plant. These use their agile lips and hand dexterity to manipulate the vegetation for the portion they want to eat. The gorillas don’t over exploit an area for food. They crop the vegetation in a manner that allows for quick replacement to occur. Gorillas have been documented using the hair on the back of their hands to absorb water and then sucking it.