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Scanning electron microscopy of earth mined and eaten by mountain gorillas in the Virunga Mountains, Rwanda

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Abstract

The sand fractions of weathered regolith (subsoil) sediments from the flanks of Visoke Volcano in the Virunga Mountains, mined, pulverized, and eaten by mountain gorillas, were analyzed by scanning electron microscope (SEM) and energy-despersive spectrometry (EDS) to determine the stimulus of geophagic behavior. The samples show a mix of weathered and volcanic minerals consisting primarily of quartz, apatite, analbite, sanidine, amphibole, ilmenite, and magnetite. The ratio of weathered to fresh grains is approximately 6:1 for the coarse sands (2 mm – 250 µm) and 13:1 for the fine fractions (63 – 250 µm) with the fresh grains very extensively fractured and abraded after grinding and rubbing by gorilla hand. In many cases the core of individual grains was exposed beneath a surface cover extensively etched by chemical weathering and often coated with Fe and Al plus clay minerals. Ground quartz grains, for example, showed surface fractures and abrasion features equivalent to microtextures produced by transport in continental glaciers. Grinding of earth materials produces a high percentage of angular fragments of fine sand size that may or may not play some role in curing intestinal ailments or countering dietary deficiencies. In particular, the grinding of earth materials shows the immense power of the gorilla hand as a pulverizing force making coarse material finer and presumably assisting in the ingesting process. The number of halloysite clay minerals present in the samples might assist in countering the effects of diarrhea.

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References

  • Cox, K. G., N. B. Price, &B. Harte, 1974.An Introduction to the Practical Study of Crystals, Minerals and Rocks. McGraw Hill, New York.

    Google Scholar 

  • Day, P., 1965. Particle fractionation and particle size analysis. In:Methods of Soil Analysis,C. A. Black (ed.), Amer. Soc. Agron., pp. 545 – 567.

  • Fossey, D., 1983.Gorillas in the Mist. Houghton Mifflin, Boston.

    Google Scholar 

  • Lacroix, A., 1992.Minéralogie de Madagascar, Vol. 2, Minéralogie Appliquée: Lithologie. Augustin Challamel, Paris.

    Google Scholar 

  • Mahaney, W. C., 1990. Glacially-crushed quartz grains in Late Quaternary deposits in the Virunga Mountains, Rwanda-indicators of wind transport from the North?Boreas, 19: 81–89.

    Google Scholar 

  • ————, 1991. Distributions of halloysite-metahalloysite and gibbsite in tropical mountain paleosols: relationship to Quaternary paleoclimate.Palaeogeogra. Palaeoclimatol. Palaeoecol., 88: 219–230.

    Google Scholar 

  • —, in press. Glacial crushing, weathering and diagenetic histories of quartz grains inferred from scanning electron microscopy. In:Glacial Environments-processes, Sediments, and Landforms,J. Menziers (ed.), Pergamon press, London.

  • ————,R. G. V. Hancock, &R. W. Barendregt, 1992. Stratigraphy, geochemistry and paleomagnetism of late Quaternary bedrock and paleosols, Karisoke area, Virunga Mountains, N-W Rwanda,Eiszeitalter Gegenwart, 42: 134–145.

    Google Scholar 

  • — &R. Sjoberg, in press. Scanning electron microscopy of quartz grains from two granite caves and a gorge system in Bohuslan, southwestern Sweden.Zeitschrift Geomorphol.

  • ————,W. B. Vortisch, &P. Julig, 1988. Relative differences between glacially crushed quartz transported by mountain and continental ice — some examples from North America and East Africa.Amer. J. Sci., 288: 810–826.

    Google Scholar 

  • ————,D. P. Watts, &R. G. V. Hancock, 1990. Geophagia by mountain gorillas (Gorilla gorilla beringei) in the Virunga Mountains, Rwanda.Primates, 31: 113–120.

    Article  Google Scholar 

  • Vermeer, D. E. &R. E. Ferrel, 1985. Nigerian geophagical clay: a traditional anti-diarrheal pharmaceutical.Science, 227: 634–636.

    CAS  PubMed  Google Scholar 

  • Vortisch, W. B., W. C. Mahaney, &K. Fecher, 1987. Lithology and relative weathering in a paleosol sequence on Mount Kenya, East Africa.Geologica Paleontol., 21: 245–255.

    Google Scholar 

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Mahaney, W.C. Scanning electron microscopy of earth mined and eaten by mountain gorillas in the Virunga Mountains, Rwanda. Primates 34, 311–319 (1993). https://doi.org/10.1007/BF02382626

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