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  • Print publication year: 2019
  • Online publication date: November 2019

8 - An energetic model of foraging optimization: wild chimpanzee hammer selection for nut-cracking


The chimpanzees of the Taï Forest, Côte d’Ivoire, crack highly nutritious Coula edulis nuts using anvils and hammers. While using tools to access encased food items provides obvious benefits, the energetic gain of tool-assisted foraging can be further increased by optimal selection of tools. Previous studies of animal tool selection often relied on implicit assumptions or theoretical arguments about how tool features would influence foraging efficiency, and comprehensive measures of actual efficiency are still missing. We used field observations of nut-cracking efficiency and previously published estimates of energetic costs to investigate the rate of net energy intake as a function of hammer weight and hammer material. While stones allowed for a generally more efficient performance, nut-cracking efficiency depended on an interaction of hammer weight and material. Relative performance of stones and wood varied according to the ripeness of the nuts. Chimpanzees’ tool selection tends to optimize nut-cracking in many respects. Nonetheless, we also observed a few mismatches between efficiency and selection, some of which may be explained on cognitive, motivational or cultural grounds.

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Aiken, L. S., West, S. G. & Reno, R. R. (1991). Multiple Regression: Testing and Interpreting Interactions. New York: Sage.
Baayen, R. H. (2008). Analyzing Linguistic Data: A Practical Introduction to Statistics using R. Cambridge: Cambridge University Press.
Barr, D. J., Levy, R., Scheepers, C. & Tily, H. J. (2013). Random effects structure for confirmatory hypothesis testing: Keep it maximal. Journal of Memory and Language, 68(3), 255278.
Bates, D., Maechler, M., Bolker, B. & Walker, S. (2014). lme4: Linear mixed-effects models using Eigen and S4. R package version, 1(7), 123.
Biro, D., Inoue-Nakamura, N., Tonooka, R., Yamakoshi, G., Sousa, C. & Matsuzawa, T. (2003). Cultural innovation and transmission of tool use in wild chimpanzees: evidence from field experiments. Animal Cognition, 6, 213223.
Boesch, C. (1991). Teaching among wild chimpanzees. Animal Behaviour, 41, 530532.–3472(05)80857–7
Boesch, C. & Boesch, H. (1981). Sex differences in the use of natural hammers by wild chimpanzees: A preliminary report. Journal of Human Evolution, 10, 585593.
Boesch, C. & Boesch, H. (1983). Optimisation of nut-cracking with natural hammers by wild chimpanzees. Behaviour, 83, 256286.
Boesch, C. & Boesch, H. (1984a). Mental map in wild chimpanzees: an analysis of hammer transports for nut cracking. Primates, 25(2), 160170.
Boesch, C. & Boesch, H. (1984b). Possible causes of sex differences in the use of natural hammers by wild chimpanzees. Journal of Human Evolution, 13, 415440.
Boesch, C. & Boesch-Achermann, H. (2000). The Chimpanzees of the Taï Forest: Behavioural Ecology and Evolution. Oxford: Oxford University Press.
Boesch, C., Bombjaková, D., Boyette, A. & Meier, A. (2017). Technical intelligence and culture: Nut cracking in humans and chimpanzees. American Journal of Physical Anthropology, 163, 339355.
Boysen, S. T. & Berntson, G. G. (1995). Responses to quantity: Perceptual versus cognitive mechanisms in chimpanzees (Pan troglodytes). Journal of Experimental Psychology: Animal Behavior Processes, 21, 82.
Bril, B., Dietrich, G., Foucart, J., Fuwa, K. & Hirata, S. (2009). Tool use as a way to assess cognition: How do captive chimpanzees handle the weight of the hammer when cracking a nut? Animal Cognition, 12, 217235.
Bruhn, J. M. & Benedict, F. G. (1936). The respiratory metabolism of the chimpanzee. Proceedings of the American Academy of Arts and Sciences, 71, 259326.
Byrne, R. W. (1997). The technical intelligence hypothesis: an additional evolutionary stimulus to intelligence. In Whiten, A. & Byrne, R. (eds.), Machiavellian Intelligence II (pp. 289–31). Cambridge: Cambridge University Press.
Dobson, A. J. & Barnett, A. (2008). An Introduction to Generalized Linear Models. Boca Raton: CRC Press.
Field, A. (2013). Discovering Statistics using IBM SPSS Statistics. New York: Sage.
Fox, J. (2002). An R and S-Plus Companion to Applied Regression. New York: Sage.
Fragaszy, D. M., Eshchar, Y., Visalberghi, E., Resende, B., Laity, K. & Izar, P. (2017). Synchronized practice helps bearded capuchin monkeys learn to extend attention while learning a tradition. Proceedings of the National Academy of Sciences of the United States of America, 114, 77987805.
Fragaszy, D. M., Greenberg, R., Visalberghi, E., Ottoni, E. B., Izar, P. & Liu, Q. (2010). How wild bearded capuchin monkeys select stones and nuts to minimize the number of strikes per nut cracked. Animal Behaviour, 80, 205214.
Goodall, J. (1964). Tool-using and aimed throwing in a community of free-living chimpanzees. Nature, 201(4926), 12641266.
Gumert, M. & Malaivijitnond, S. (2013). Long-tailed macaques select mass of stone tools according to food type. Philosophical Transactions of the Royal Society B, 368 (1630).
Günther, M. M. & Boesch, C. (1993). Energetic cost of nut cracking behaviour in wild chimpanzees. In Preuschoft, H. & Chivers, D. J. (eds.), Hands of Primates (pp. 109129). Vienna: Springer.
Harmand, S., Lewis, J. E., Feibel, C. S., Lepre, C. J., Prat, S., Lenoble, A., et al. (2015). 3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya. Nature, 521(7552), 310315.
Luncz, L.V. & Boesch, C. (2014). Tradition over trend: Neighboring chimpanzee communities maintain differences in cultural behavior despite frequent immigration of adult females. American Journal of Primatology, 76, 649657.
Luncz, L. V., Falotico, T., Pascual-Garrido, A., Corat, C., Mosley, H. & Haslam, M. (2016b). Wild capuchin monkeys adjust stone tools according to changing nut properties. Scientific Reports, 6, 33089.
Luncz, L. V., Mundry, R. & Boesch, C. (2012). Evidence for cultural differences between neighboring chimpanzee communities. Current Biology, 22, 922926.
Luncz, L. V., Proffitt, T., Kuhlik, L., Haslam, M. & Wittig, R. M. (2016a). Distance-decay effect in stone tool transport by wild chimpanzees. Proceedings of the Royal Society B, 283(1845).
Luncz, L. V., Sirianni, G., Mundry, R. & Boesch, C. (2018). Costly culture: differences in nut-cracking efficiency between wild chimpanzee groups. Animal Behaviour, 137, 6373.
Luncz, L. V., Wittig, R. M. & Boesch, C. (2015). Primate archaeology reveals cultural transmission in wild chimpanzees (Pan troglodytes verus). Philosophical Transactions of the Royal Society B, 370(1682), 20140348.
Mangalam, M. & Fragaszy, D. M. (2015). Wild bearded capuchin monkeys crack nuts dexterously. Current Biology, 25, 13341339.
Matsuzawa, T. (1985). Use of numbers by a chimpanzee. Nature, 315(6014), 5759.
Matsuzawa, T. (1996). Chimpanzee intelligence in nature and in captivity: isomorphism of symbol use and tool use. In McGrew, W. C., Marchant, L. F. & Nishida, T. (eds.), Great Ape Societies (pp. 196209). New York: Cambridge University Press.
Mercader, J., Panger, M. & Boesch, C. (2002). Excavation of a chimpanzee stone tool site in the African rainforest. Science, 296(5572), 14521455.
Möbius, Y., Boesch, C., Koops, K., Matsuzawa, T. & Humle, T. (2008). Cultural differences in army ant predation by West African chimpanzees? A comparative study of microecological variables. Animal Behaviour, 76, 3745.
Navarrete, A. F., Reader, S. M., Street, S. E., Whalen, A. & Laland, K. N. (2016). The coevolution of innovation and technical intelligence in primates. Philosophical Transactions of the Royal Society B, 371(1690).
Neufuss, J., Humle, T., Cremaschi, A. & Kivell, T. L. (2017). Nut-cracking behaviour in wild-born, rehabilitated bonobos (Pan paniscus): A comprehensive study of hand-preference, hand grips and efficiency. American Journal of Primatology, 79(2), 116.
Pandolf, K. B., Givoni, B. & Goldman, R. F. (1977). Predicting energy expenditure with loads while standing or walking very slowly. Journal of Applied Physiology, 43, 577581.
Quinn, G. P. & Keough, M. J. (2002). Experimental Design and Data Analysis for Biologists. Cambridge: Cambridge University Press.
R Core Team. (2014). R: A Language and Environment for Statistical Computing. Vienna: R Foundation for Statistical Computing.
Sanz, C. M., Call, J. & Boesch, C. (eds.). (2013). Tool Use in Animals: Cognition and Ecology. Cambridge: Cambridge University Press.
Schielzeth, H. (2010). Simple means to improve the interpretability of regression coefficients. Methods in Ecology and Evolution, 1, 103113.
Schielzeth, H. & Forstmeier, W. (2008). Conclusions beyond support: Overconfident estimates in mixed models. Behavioral Ecology, 20, 416420.
Sirianni, G., Mundry, R. & Boesch, C. (2015). When to choose which tool: Multidimensional and conditional selection of nut cracking hammers in wild chimpanzees. Animal Behaviour, 100, 152165.
Sirianni, G., Wittig, R., Gratton, P., Mundry, R., Schüler, A. & Boesch, C. (2018). Do chimpanzees anticipate object’s weight? A field experiment on the kinematics of hammer-lifting movements in the nut cracking Taï chimpanzees. Animal Cognition, 21, 109.–1144–0
Soiret, S. P., Kadjo, B., Assi, B. D. & Kouassi, P. K. (2015). New observations in nut cracking behavior of chimpanzees (Pan troglodytes verus) in Djouroutou, Taï National Park. International Journal of Innovation and Applied Studies, 11, 15.
Spagnoletti, N., Visalberghi, E., Ottoni, E., Izar, P. & Fragaszy, D. (2011). Stone tool use by adult wild bearded capuchin monkeys (Cebus libidinosus). Frequency, efficiency and tool selectivity. Journal of Human Evolution, 61, 97107.
Spitzer, H., Hettinger, T. & Kaminsky, G. (1982). Tafeln für den Energieumsatz bei körperlicher Arbeit. Beuth.
Sugiyama, Y. & Koman, J. (1979). Tool-using and -making behavior in wild chimpanzees at Bossou, Guinea. Primates, 20, 513524.
Tan, A. W. Y. (2017). From play to proficiency: The ontogeny of stone tool-use in coastal-foraging long-tailed macaques (Macaca fascicularis) from a comparative perception-action perspective. Journal of Comparative Psychology, 131, 89114.
Tebbich, S., Taborsky, M., Fessl, B. & Dvorak, M. (2002). The ecology of tool use in the woodpecker finch (Cactospiza pallida). Ecology Letters, 5, 656664.
Visalberghi, E., Addessi, E., Truppa, V., Spagnoletti, N., Ottoni, E., Izar, P., et al. (2009). Selection of effective stone tools by wild bearded capuchin monkeys. Current Biology, 19, 213217.
Visalberghi, E., Sabbatini, G., Spagnoletti, N., Andrade, F. R. D. D., Ottoni, E., Izar, P., et al. (2008). Physical properties of palm fruits processed with tools by wild bearded capuchins (Cebus libidinosus). American Journal of Primatology, 70, 884891.
Visalberghi, E., Sirianni, G., Fragaszy, D. & Boesch, C. (2015). Percussive tool use by Taï Western chimpanzees and Fazenda Boa Vista bearded capuchin monkeys: a comparison. Philosophical Transactions of the Royal Society B, 370(1682), 20140351.