Chemical correlates of rhesus monkey food choice: The influence of hydrolyzable tannins.

Feeding behavior was quantified of free-ranging adult rhesus monkeys in the Himalayan foothills of northern Pakistan. Twenty-eight food and 63 nonfood plant samples were collected and analyzed for tannins, alkaloids, fiber, lignin, protein, amino acids, total nonstructural carbohydrates, and free glucose. Most major foods of the rhesus were low in tannins and high in nutrients. The rhesus ate mainly parts of herbaceous plants, although woody plants were more abundant, possibly because herbs were lower in condensed tannins than woody plants. Feeding was negatively correlated with the astringency of tannins, ellagitannins, and total phenolics among all samples. Among leaves of both herbs and woody plants, feeding was negatively correlated with measures of hydrolyzable tannins. Total protein, total nonstructural carbohydrates, and water were not related to food choice and may not have been limiting at the site.