Wild chimpanzees select tool material based on efficiency and knowledge
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Some animals have basic culture, but to date there is not much evidence that cultural traits evolve as part of a cumulative process as seen in humans. This may be due to limits in animal physical cognition, such as an inability to compare the efficiency of a novel behavioural innovation with an already existing tradition. We investigated this possibility with a study on a natural tool innovation in wild chimpanzees: moss-sponging, which recently emerged in some individuals to extract mineral-rich liquids at a natural clay-pit. The behaviour probably arose as a variant of leaf-sponging, a tool technique seen in all studied chimpanzee communities. We found that moss-sponges not only absorbed more liquid but were manufactured and used more rapidly than leaf-sponges, suggesting a functional improvement. To investigate whether chimpanzees understood the advantage of moss- over leaf-sponges, we experimentally offered small amounts of rainwater in an artificial cavity of a portable log, together with both sponge materials, moss and leaves. We found that established moss-spongers (having used both leaves and moss to make sponges) preferred moss to prepare a sponge to access the rainwater, whereas leaf-spongers (never observed using moss) preferred leaves. Survey data finally demonstrated that moss was common in forest areas near clay-pits but nearly absent in other forest areas, suggesting that natural moss-sponging was at least partly constrained by ecology. Together, these results suggest that chimpanzees perceive functional improvements in tool quality, a crucial prerequisite for cumulative culture.
Lamon , N , Neumann , C , Gier , J , Zuberbühler , K & Gruber , T 2018 , ' Wild chimpanzees select tool material based on efficiency and knowledge ' , Proceedings of the Royal Society B: Biological Sciences , vol. 285 , no. 1888 , 20181715 . https://doi.org/10.1098/rspb.2018.1715
Proceedings of the Royal Society B: Biological Sciences
© 2018, The Author(s) Published by the Royal Society. This work has been made available online in accordance with the publisher’s policies. This is the author created accepted version manuscript following peer review and as such may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1098/rspb.2018.1715
DescriptionThis work was funded by the European Research Council (FP7/2007-2013/ERC n°283871) and the Swiss National Science Foundation (grants 310030_143359 to KZ; CR13I1_162720 and P300PA_164678 to TG).
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