Cognitive capacities for behavioural flexibility in wild chimpanzees (Pan troglodytes): the effect of snare injury on complex manual food processing |
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Authors: | Emma J Stokes Richard W Byrne |
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Institution: | (1) Scottish Primate Research Group, University of St Andrews, School of Psychology, St Andrews, Fife KY16 9JU, Scotland,;(2) Present address: Wildlife Conservation Society, Mbeli Bai Study, Nouabalé-Ndoki Projet, BP14537, Brazzaville, Republic of Congo, |
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Abstract: | In chimpanzees, it is only in the restricted context of tool use that manual and cognitive skills have been described, comparable
to those that gorillas and orang-utans display in obtaining plant foods. We report the complex food preparation skills used
to eat, without tools, the leaves of the tree Broussonettia papyrifera in the Sonso community of chimpanzees at Budongo Forest, Uganda. Able-bodied individuals used multi-stage techniques that
required bimanual role differentiation at several stages, and were hierarchical in organisation. A total repertoire of 14
techniques was found, with strong preference in all individuals for either of two of these; 6 additional techniques were found
when flowers and leaves were eaten together. However, in this community over 20% of individuals suffer from some form of upper-
or lower-limb injury as a result of snares. We investigated the manner of compensation for upper-limb injury. Only the most
severely injured showed reduced feeding efficiency. Injured individuals were found to use the same repertoire of techniques
as able-bodied chimpanzees. We found no evidence to suggest that injured individuals were able to develop wholly novel techniques
optimal for their specific injuries, although shifts in preference for particular techniques did occur. Rather, injured individuals
used novel ways of achieving particular steps in the process; by "working around" their impairments; in this way, they managed
to use the same techniques as the able-bodied. Since snare injuries generally befall young animals, these results suggest
that chimpanzees learn techniques partly through observational learning (of, necessarily, able-bodied individuals).
Accepted after revision: 8 February 2001
Electronic Publication |
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Keywords: | Chimpanzee Feeding technique Injury Hierarchical organization Imitation |
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