Data from: Daily protein prioritization and longterm nutrient balancing in a dietary generalist, the blue monkey

Animals must make dietary choices to achieve adequate nutrient intake,
however it is challenging to study in the field 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 the intake of nutrients, specifically
non-protein energy and available protein (hereafter, 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 adult females in
Kakamega Forest, Kenya. Subjects exhibited short- and long-term
nutritional strategies. On a daily basis, they balanced non-protein energy
to protein intake but when balancing was impossible, monkeys prioritized
protein intake. Over the long-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
of nutrient balancing in primates suggests that diverse dietary strategies
evolved to allow adherence to a balance of non-protein energy:protein
despite various social and environmental constraints. The data from this
study also add to a small but growing number of studies that document
nutritional strategies in wild animal populations.