Metabolomic data suggest regulation of black howler monkey (Alouatta pigra) diet composition at the molecular level

In addition to macronutrients, foods consist of a complex set of chemical compounds that can influence dietary selectivity and consumer physiology. Metabolomics allow us to describe this complexity by quantifying all small molecules, or metabolites, in a food item. In this study we use GC-MS based metabolomics to describe the metabolite profiles of foods consumed by one population of Mexican black howler monkeys (Alouatta pigra) over a 10-month period. Our data indicate that each food exhibited a distinct metabolite profile, and the average weekly intake of metabolites such as neochlorogenic acid and serotonin (5-hydroxytryptamine) was correlated with the consumption of certain plant parts. We speculate that these patterns result in temporal changes in howler monkey physiology such as food retention time. In contrast, variation in the weekly intake of metabolites such as oxalic acid was 70% less than variation in the concentration of the same metabolites across food items, suggesting that howler monkeys regulated the intake of these metabolites, possibly to avoid physiological consequences such as kidney stone formation. Finally, seasonal variation in the consumption of individual nutrient and non-nutrient metabolites were correlated with changes in the relative abundances of associated gut microbial taxa, implying indirect effects of food item metabolites on howler monkey nutritional ecology that likely drive foraging decisions. While additional research is needed to validate these findings, the patterns we report serve as important baseline data for understanding the effects of plant metabolites on the food choice in primates.