Daily protein prioritization and long-term nutrient balancing in a dietary generalist, the blue monkey

• Published in: Behavioral ecology Vol. 32; no. 2; pp. 223 - 235
• Main Authors: Takahashi, Maressa Q, Rothman, Jessica M, Raubenheimer, David, Cords, Marina
• Format: Journal Article
• Language: English
• Published: UK Oxford University Press 01.03.2021
• Subjects: nutritional ecology; intake target; dietary strategy; guenon; nutritional geometry framework
• ISSN: 1045-2249; 1465-7279
• DOI: 10.1093/beheco/araa120

Abstract Animals make dietary choices to achieve adequate nutrient intake; however, it is challenging to study such nutritional strategies in wild populations. We explored the nutritional strategy of a generalist social primate, the blue monkey (Cercopithecus mitis). We hypothesized that females balance intake of nutrients, specifically non-protein energy and protein, both on a daily and long-term basis. When balancing was not possible, we expected subjects to prioritize constant protein intake, allowing non-protein energy to vary more. To understand the ecology of nutrient balancing, we examined how habitat use, food availability, diet composition, social dominance rank, and reproductive demand influenced nutrient intake. Over 9 months, we conducted 371 all-day focal follows on 24 subjects in Kakamega Forest, Kenya. Females exhibited short- and long-term nutritional strategies. Daily, they balanced non-protein energy to protein intake but when balancing was impossible, monkeys prioritized protein intake. Longer term, they balanced non-protein energy:protein intake in a 3.8:1 ratio. The ratio related positively to fruit in the diet and negatively to time in near-natural forest, but we found no evidence that it related to food availability, reproductive demand, or dominance rank. Lower-ranked females had broader daily diets, however, which may reflect behavioral feeding strategies to cope with social constraints. Overall, females prioritized daily protein, allowing less variation in protein intake than other aspects such as non-protein energy:protein ratio and non-protein energy intake. The emerging pattern in primates suggests that diverse dietary strategies evolved to allow adherence to a nutrient balance of non-protein energy:protein despite various social and environmental constraints. Animals must make dietary choices to achieve adequate nutrient intake, but studying nutrient strategies is challenging in the field. Using behavioral and laboratory data, we show that a generalist primate, the blue monkey, used distinct daily and long-term strategies to achieve such intake. Daily, female subjects prioritized consuming protein (i.e., maintained relatively constant intake). Over multiple months, however, subjects balanced intake of non-protein energy (carbohydrates and fat) and protein, despite potential environmental and social constraints.