Archaeol – a biomarker for foregut fermentation in modern and ancient herbivorous mammals?

A pilot study was conducted to investigate the hydroxylated lipid content of faeces from a range of herbivorous animals with either foregut or hindgut fermenting digestive systems. Assessment of the sterol distributions derived from the faeces revealed that, whilst there were differences in the relative concentrations of individual compounds between species, there was no overall characteristic that could be used to differentiate between foregut and hindgut fermenters. However, the concentration of archaeol in each of the modern faeces varied between 5 and 49 μg g−1dry wt for the foregut fermenters, whilst archaeol was not detected in faeces from hindgut fermenters. Based on these results, it is proposed that archaeol might be a useful proxy for methanogenesis in foregut fermenting digestive systems and, further, that the presence of archaeol may be used to infer a foregut digestive origin for coprolites from ancient herbivores. Consistent with this proposal, analysis of a sub-fossil ovi-caprid coprolite yielded detectable quantities of archaeol.