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Food selection by folivorous primates is thought to relate to macronutrients, micronutrients and plant secondary metabolites. However, few studies explain their effects on food choices. This study was designed to clarify the effect of phytochemical components on Rhinopithecus bieti food choice by analyzing the chemical composition of food samples collected from March to May in 2010 and 2011 at Mt. Lasha in northwest Yunnan, China. Compared with non-foods, there was more phosphorous and crude protein, less total sugar and a lower ratio of calcium to phosphorus in selected foods. However, no differences were found in crude fat, crude ash, calcium and tannin content between foods and non-foods. Phytochemical constituents may influence food choices; the monkeys preferred foods with high phosphorus and low Ca/P, low calcium, low sugar and low tannins. Rhinopithecus bieti foraged high quality foods such as buds and young leaves to meet their nutritional needs after a long winter. Therefore, if tannin content in food did not exceed the enduring threshold of R. bieti, the nutrient intake was prioritized by phosphorus and calcium regulation when the need for macronutrients dominated by protein was satisfied.

Copulation patterns are important to understanding male mating strategies and stabilization strategies of social organizations in primates. However, information on copulation patterns of Asian primates is relatively rare. This study was undertaken to collect data on mating behavior and birth seasonality of Black-and-white Snub-nosed monkeys (Rhinopithecus bieti) using all occurrence sampling and Focal animal-scan sampling methods at Mt. Lasha, between January and December, 2011. Our study focused on observing mating frequency and birth rates. Snub-nosed monkeys mate year round, with two observable peaks: one reproductive peak during the mating season, roughly from August to October, and a second non-breeding peak during the birth season. It is unclear what biological significance this non-reproductive mating peak has. During our observation, we noted a lower ratio of mount to ejaculation and rare ejaculatory copulations, which indicated that every mating would not result in ejaculation. This study corroborates the previous view that the Rhinopithecus bieti's copulatory pattern is likely multiple-mount ejaculation (MME) or at the upper part of mating continuum of single-mount ejaculation (SME) toward MME. More ejaculatory copulations initiated by males than females indicate that MME is not only a mating strategy of males, but that males can influence the position of their copulatory pattern on the continuum between SME and MME. The mating frequencies significantly correlated with the birth rates with a delay of 6 to 7 months. Monkeys gave birth within a strict seasonality with a birth peak of March, which confirms the previous view. Infants were born with a certain degree of synchronization, but different populations displayed different modes of synchronizations.