Environmental Geochemistry and Health

, Volume 41, Issue 6, pp 2911–2927 | Cite as

Geophagy among East African Chimpanzees: consumed soils provide protection from plant secondary compounds and bioavailable iron

  • Paula A. PebsworthEmail author
  • Stephen Hillier
  • Renate Wendler
  • Ray Glahn
  • Chieu Anh Kim Ta
  • John T. Arnason
  • Sera L. Young
Original Paper


Geophagy, the intentional consumption of earth materials, has been recorded in humans and other animals. It has been hypothesized that geophagy is an adaptive behavior, and that clay minerals commonly found in eaten soil can provide protection from toxins and/or supplement micronutrients. To test these hypotheses, we monitored chimpanzee geophagy using camera traps in four permanent sites at the Budongo Forest Reserve, Uganda, from October 2015–October 2016. We also collected plants, and soil chimpanzees were observed eating. We analyzed 10 plant and 45 soil samples to characterize geophagic behavior and geophagic soil and determine (1) whether micronutrients are available from the soil under physiological conditions and if iron is bioavailable, (2) the concentration of phenolic compounds in plants, and (3) if consumed soils are able to adsorb these phenolics. Chimpanzees ate soil and drank clay-infused water containing 1:1 and 2:1 clay minerals and > 30% sand. Under physiological conditions, the soils released calcium, iron, and magnesium. In vitro Caco-2 experiments found that five times more iron was bioavailable from three of four soil samples found at the base of trees. Plant samples contained approximately 60 μg/mg gallic acid equivalent. Soil from one site contained 10 times more 2:1 clay minerals, which were better at removing phenolics present in their diet. We suggest that geophagy may provide bioavailable iron and protection from phenolics, which have increased in plants over the last 20 years. In summary, geophagy within the Sonso community is multifunctional and may be an important self-medicative behavior.


Soil eating Detoxification Micronutrients Primates Simulated digestion 



PAP thanks the Budongo Conservation Field Station staff, field assistants, and in particular Vernon Reynolds, Fred Babweteera, Klaus Zuberbühler, Catherine Hobaiter, Jakob Villioth, Geoffrey Muhanguzi, Geresomu Muhumuza, Jacob Alio, and Michael Jurua for field and data assistance. We also thank the Royal Zoological Society of Scotland who provided core funding and the Uganda Wildlife Authority and the Ugandan Council of Science and Technology for the opportunity of conduct research in Uganda. We thank David Emerson, Rui Liu, Nia Gray, Mary Bodis, Pei–Pei Chang, Nimal De Silva, Jean Bjornson, Christopher Boddy, and Joseph Ndawula for assistance with laboratory analyses. We further thank Thad Bartlett, Josh Miller, Chris and Diane West for manuscript assistance and logistical support. SH and RW acknowledge support of the Scottish Government’s Rural and Environment Science and Analytical Services Division (RESAS). JTA acknowledges support from the Canadian Natural Science and Engineering Research Council. Finally, we thank Environmental Geochemistry and Health, Professor William Mahaney, and two anonymous reviewers for their valuable advice and helpful comments on a previous version of this article.


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Copyright information

© Springer Nature B.V. 2019

Authors and Affiliations

  1. 1.Department of AnthropologyThe University of TexasSan AntonioUSA
  2. 2.National Institute of Advanced StudiesIndian Institute of Science CampusBangaloreIndia
  3. 3.James Hutton InstituteCraigiebuckler, AberdeenScotland, UK
  4. 4.Department of Soil and EnvironmentSwedish University of Agricultural Sciences, SLUUppsalaSweden
  5. 5.Robert Holley Center for Agriculture and HealthIthacaUSA
  6. 6.Department of BiologyUniversity of OttawaOttawaCanada
  7. 7.Department of Anthropology and Institute for Policy ResearchNorthwestern UniversityEvanstonUSA

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