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An experimental study of leaf swallowing in captive chimpanzees: insights into the origin of a self-medicative behavior and the role of social learning

Abstract

Chimpanzees in the wild swallow the rough hispid leaves of certain plant species as a means of physically expelling intestinal parasites. A plant with such a leaf texture was introduced in 36 trial sessions to a captive group of 11 healthy adult chimpanzees to investigate the possible origin and acquisition of leaf swallowing behavior. One male (housed separately from the group during testing) and one female, both captive born, spontaneously exhibited the behavior on their first trial without prior opportunity to observe others with this plant. Six other chimpanzees on their first trial displayed a phobic response to these leaves and rejected them entirely, while another two chewed and swallowed the leaves in a normal way. Four individuals eventually exhibited the behavior, after having approached and closely observed the leaf swallowing of the first female to exhibit the behavior in the group. Four of the six individuals that initially avoided the leaves never overcame their phobia toward this plant and were not in proximity to a chimpanzee performing leaf swallowing during test sessions. Individuals born to wild chimpanzee mothers were no more likely to perform the behavior than captive-reared group mates. These results suggest that the acquisition of this behavior is based in part on a propensity to fold and swallow rough, hispid leaves, but that the acquisition and spread of leaf swallowing within a group is likely to be socially influenced. This study provides support for the hypothesis that leaf swallowing originated in the wild from opportunistic feeding behavior and was later passed down in the form of a self-medicative behavioral tradition.

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References

  1. Coussi-Korbel S, Fragaszy DM (1995) On the relationship between social dynamics and social learning. Anim Behav 50:1441–1453

  2. Ginsberg JR, Young TP (1992) Measuring association between individuals or groups in behavioural studies. Anim Behav 44:377–379

  3. Huffman MA (1997) Current evidence for self-medication in primates: a multidisciplinary perspective. Yearb Phys Anthropol 40:171–200

  4. Huffman MA (2001) Self-medicative behavior in the African great apes: an evolutionary perspective into the origins of human traditional medicine. BioScience 51:651–661

  5. Huffman MA, Caton JM (2001) Self-induced increase of gut motility and the control of parasitic infections in wild chimpanzees. Int J Primatol 22:329–346

  6. Huffman MA, Hirata S (2003) Biological and ecological foundations of primate behavioral traditions. In: Fragaszy DM, Perry S (eds) The biology of tradition: models and evidence. Cambridge University Press, Cambridge, pp 267–296

  7. Huffman MA, Quiatt D (1986) Stone handling by Japanese macaques (Macaca fuscata): implications for tool use of stone. Primates 27:413–423

  8. Huffman MA, Seifu M (1989) Observations on the illness and consumption of a medicinal plant Vernonia amygdalina by a wild chimpanzee in the Mahale Mountains, Tanzania. Primates 30:51–63

  9. Huffman MA, Wrangham RW (1994) Diversity of medicinal plant use by chimpanzees in the wild. In: Wrangham RW, McGrew WC, deWaal FB, Heltne PG (eds) Chimpanzee cultures. Harvard University Press, Cambridge, Mass., pp 129–148

  10. Huffman MA, Page JE, Sukhdeo MVK, Gotoh S, Kalunde MS, Chandrasiri T, Towers GHN (1996) Leaf-swallowing by chimpanzees: a behavioral adaptation for the control of strongyle nematode infections. Int J Primatol 72:475–503

  11. Karban R, English-Loeb G (1997) Tachinid parasitoids affect host plant choice by caterpillars to increase caterpillar survival. Ecology 78:603–611

  12. Ochiai T, Matsuzawa T (1998) Planting trees in an outdoor compound of chimpanzees for an enriched environment. In: Hare VL, Worley KE (eds) Proceedings of the third international conference on environmental enrichment. The Shape of Enrichment, San Diego, Calif., pp 355–364

  13. Ochiai T, Matsuzawa T (1999) Environmental enrichment for captive chimpanzees (Pan troglodytes): introduction of climbing frames 15 m high. Primate Res 15:289–296

  14. Schaik CP van (2003) Local traditions in orangutan and chimpanzees: social learning and social tolerance. In: Fragaszy DM, Perry S (eds) The biology of tradition: models and evidence. University of Cambridge Press, Cambridge, pp 297–328

  15. Schaik CP van, Deaner RO, Merrill MY (1999) The conditions for tool use in primates: implications for the evolution of material culture. J Hum Evol 36:719–741

  16. Visalberghi E, Fragaszy DM (1990) Food washing behaviour in tufted capuchin monkeys, Cebus apella, and crab eating macaques, Macaca fuscicularis. Anim Behav 40:829–836

  17. Vitazkova SK, Long E, Paul A, Glendinning JI (2001) Mice suppress malaria infection by sampling ‘bitter’ chemotherapy agent. Anim Behav 61:887–894

  18. White FJ, Burgman MA (1990) Social organization of the pygmy chimpanzee (Pan paniscus): multivariate analysis of intracommunity associations. Am J Phys Anthropol 83:193–201

  19. Whitehead H (1997) Analysing animal social structure. Animal Behav 53:1053–1067

  20. Wrangham RW (1995) Relationship between chimpanzee leaf swallowing to a tapeworm infection. Am J Primatol 37:297–303

  21. Wrangham RW, Nishida T (1983) Aspilia spp. leaves: a puzzle in the feeding behavior of wild chimpanzees. Primates 24:276–282

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Acknowledgements

We wish to give our sincere thanks to Testuro Matsuzawa, Professor of the Section of Language and Intelligence (PRI) and Professor Iver Iversen of Northern Florida State University, for their encouragement and support in conducting this study. We are indebted to the primate health care staff of the Center for Human Evolution Modeling Research for their assistance and day-to-day care of the chimpanzees. The present research was partially financed by Grants 07102010, 12301006, and 10CE2005 from the Ministry of Education, Science, Sports, and Culture, Japan. We thank our anonymous referees and Jean-Baptiste Leca for their insightful comments and criticisms of the manuscript in its final stages. Last but not least, we thank the chimpanzees for their patience and cooperation, without which this study would not have been possible.

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Correspondence to Michael A. Huffman.

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Huffman, M.A., Hirata, S. An experimental study of leaf swallowing in captive chimpanzees: insights into the origin of a self-medicative behavior and the role of social learning. Primates 45, 113–118 (2004). https://doi.org/10.1007/s10329-003-0065-5

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Keywords

  • Feeding
  • Social tolerance
  • Behavioral tradition
  • Self-medication