Cafeteria‐style feeding trials provide new insights into the diet and nutritional strategies of the black snub‐nosed monkey (Rhinopithecus strykeri): Implications for conservation

Abstract

Anthropogenic changes and fragmentation of natural habitats often exert a negative effect on resource availability and distribution, and the nutritional ecology and feeding behavior of nonhuman primates. The goals of this study are to examine food choice and to identify the nutritional profile of foods consumed by the Critically Endangered black snub‐nosed monkey (Rhinopithecus strykeri). To accomplish our study goals, we presented cafeteria‐style feeding trials of fresh food items collected in the home range of wild black snub‐nosed monkeys to the only two captive R. strykeri, and compared the nutritional profiles of the leafy foods (buds, young, and mature leaves, 100 items from 70 plant species) selected with those avoided (54 items from 48 plant species). Overall, the results indicate that captive R. strykeri selected foods that were higher in moisture (Mo; 77.7%), crude protein (CP; 21.2%), total nonstructural carbohydrates (TNC; 34.9%), and phosphorus (P; 0.37%) while tending to avoid foods with a neutral detergent fiber (NDF) content of greater than 46.8%. Leaves collected in autumn and selected by the monkeys were characterized by a slightly higher amount of metabolizable energy (ME) than those rejected (1,350 kJ/100 g vs. 1,268 kJ/100 g). In contrast, the protein content of foods collected and consumed during the spring was greater (22.9%) than in autumn (16.4%). Random Forests modeling, an ensemble learning method, indicated that the proportion of Mo, NDF, ME, CP, P, and TNC were among the most important factors in predicting which items were consumed by the captive R. strykeri during spring and autumn. On the basis of the nutritional profile of foods consumed across the two seasons, we identified 18 nutrient‐rich native plant species that we recommend for use in ex‐ and in‐situ conservation management and reforestation programs to provide long‐term access to a nutritionally adequate diet.

Methodological limitations and conceptual implications of nutritional estimations

“…This ranking approach is often used also in applied context to assess carrying capacity, determine habitat suitability and explain consumers' movement patterns. For instance, Yang et al (2020) estimated the nutritional content of various foods that were selected or avoided by the black snub‐nosed monkey Rhinopithecus strykeri as a way to determine what plant species to use in conservation management and reforestation programs. We claim that since different methods can yield different nutritional rankings for different taxa, the methods of choice can very much influence the study conclusions.…”

The 10th anniversary of the scientific description of the black snub‐nosed monkey (Rhinopithecus strykeri): It is time to initiate a set of new management strategies to save this critically endangered primate from extinction

“…Based on the currently available evidence, the diet of R. strykeri appears to be generally similar to the diets of other species of snub‐nosed monkeys, and includes a mix of leaves, lichens, fruits, seeds, flowers, and bamboo shoots that contain a high concentration of moisture, protein, carbohydrates and minerals (Yang et al, 2019a; 2020). Lichenivory is one of the most distinctive dietary adaptations of R. bieti and R. roxellana (Grueter et al, 2009; Guo et al, 2007; Yang et al, 2019a).…”

Nutrient-sensitive reinforcement learning in monkeys

“…Because nutrients are mainly acquired from food intake, an animal's ability to adapt its food choice to changing nutrient availabilities critically determines its nutrient balance and long-term health. To optimize nutrient intake, foraging animals adapt their feeding patterns in response to regional and seasonal variations of food resources [14][15][16] . For instance, monkeys spend more time in food patches associated with a high probability of nutritious foods (e.g., nuts) while ignoring more frequent low-nutrient foods (e.g., leaves).…”