6 - Object manipulation and skill organization in the complex food preparation of mountain gorillas  pp. 147-159

Object manipulation and skill organization in the complex food preparation of mountain gorillas

By Richard W. Byrne

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In his monograph on the mountain gorilla of the Virunga Volcanoes, Schaller describes how gorillas eat over thirty different foods (Schaller, 1963, pp. 156–165). The accounts are brief, and sometimes based on only a very few observations. Nevertheless, it is immediately clear to the reader that interestingly different techniques are involved with each plant.

Some, such as the vine Droquetia iners, are “merely pushed into the mouth.” Almost as little care is taken with small ferns Polypodium sp.: to eat them a gorilla “reaches below the branch and without looking grabs a handful of the hanging ferns which it pulls in. After severing and discarding the roots with one bite, it stuffs the greens into its mouth.” Biting off encasing material is a method used in several different ways to detach inedible, contaminated, or, occasionally edible parts. Bark from the tree fern Cyathea deckenii is bitten off and discarded in small piles, and only the tender inside is eaten; taproots of the herbs Cynoglossum amplifolium and C.geometricum are hauled out of the ground and their tough bark is bitten off before consumption; in contrast, the dry bark of Hagenia and Hypericum trees is bitten off, but consumed.

Other plants evidently present more challenge to preparation. Often, this is a consequence of the relatively greater hardness and toughness of the encasing material compared with the fragile but edible interior. Schaller noted that feeding remains of bamboo Arundinaria alpine suggest that the tough and hairy outer layers are “peeled back to expose the pith, much as a human prepares a banana.”