Comparative microbial analysis and clay mineralogy of soils eaten by chimpanzees (Pan troglodytes schweinfurthii) in Tanzania

The abundance of culturable microorganisms in Tanzanian termite mound soils similar to those eaten by chimpanzees (Pan troglodytes schweinfurthii) was compared with corresponding non-eaten soils using a serial dilution plating method. Additionally, the particle size distribution and clay mineralogy of the soils were examined. The microbiology of these soils was examined as a preliminary step to investigate the hypothesis that this behaviour relates to self-medication with antibiotics. Significantly higher (P=0.037) numbers of filamentous bacteria (actinomycetes), were detected in termite mound soils relative to control soils, but numbers of non-filamentous bacteria and fungi did not differ between the two groups. The clay content was significantly higher (P=0.007) in eaten soils, but the mineralogy of the less than 2 μm fraction was similar for all soils. This study suggests that if chimpanzees selectively consume soils based on their content characteristics, the importance of the type of clay minerals may be secondary to the overall clay content.