Geographic variation in tool use on Neesia fruits in orangutans.

Bibliographic Collection: 
MOCA Reference, APE
Publication Type: Journal Article
Authors: van Schaik, C P; Knott, C D
Year of Publication: 2001
Journal: Am J Phys Anthropol
Volume: 114
Issue: 4
Pagination: 331-42
Date Published: 2001 Apr
Publication Language: eng
ISSN: 0002-9483
Keywords: Animals, Feeding Behavior, Fruit, Geography, Indonesia, Motor Skills, Pongo pygmaeus, Seeds

Geographic variation in the presence of skilled behavior may reflect geographic variation in genetic predispositions or ecological conditions (accompanied by reliable expression during development), or it may reflect the vagaries of invention and the appropriate social conditions for persistence. In this study, we compare the feeding techniques and tool-using skills used by orangutans to extract the nutritious seeds from Neesia fruits between Suaq Balimbing on Sumatra and Gunung Palung on Borneo, and map the distribution of Neesia tool use in Sumatran swamps. We show that neither genetics nor ecology is sufficient to explain the distribution of this tool use, confirming earlier findings on chimpanzees. We conclude that the ability to learn to use tools determines the geographic distribution. It is impossible to distinguish between the history of invention and the conditions for social transmission as the causal factors, but the high density and the social tolerance at Suaq Balimbing create propitious conditions for the maintenance of the skill as a tradition once it has been invented. High orangutan densities in the other Sumatran coastal swamps with Neesia tool use support the conclusion that suitable transmission conditions are the critical factor to explain the geographic distribution of skills such as feeding tool use.

DOI: 10.1002/ajpa.1045
Alternate Journal: Am. J. Phys. Anthropol.
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