Chemistry, mineralogy and microbiology of termite mound soil eaten by the chimpanzees of the Mahale Mountains, Western Tanzania

Subsamples of termite mound soil used by chimpanzees for geophagy, and tops oil never ingested by them, from the forest floor in the Mahale Mountains N ational Park, Tanzania, were analysed to determine the possible stimulus or stimuli for geophagy. The ingested samples have a dominant clay texture eq uivalent to a claystone, whereas the control samples are predominantly sand y clay loam or sandy loam, which indicates that particle size plays a signi ficant role in soil selection for this behaviour. One potential function of the clays is to bind and adsorb toxins. Although both termite mound and co ntrol samples have similar alkaloid-binding capacities, they are in every c ase very high, with the majority of the samples being above 80%. The clay s ize material (<2 mu m) contains metahalloysite and halloysite, the latter a hydrated aluminosilicate (Al2Si2O4. nH(2)O), present in the majority of bo th the termite mound soil and control soil samples. Metahalloysite, one of the principal ingredients found in the pharmaceutical Kaopectate(TM), is us ed to treat minor gastric ailments in humans. The soils commonly ingested c ould also function as antacids, as over half had pH values between 7.2 and 8.6. The mean concentrations of the majority of elements measured were grea ter in the termite mound soils than in the control soils. The termite mound soils had more filamentous bacteria, whereas the control soils contained g reater numbers of unicellular bacteria and fungi.