Date of Degree
Jessica M. Rothman
Andrea L. Baden
Biological and Physical Anthropology
primate diet, primate nutrition, guenon, insectivory, social nutrition
An animal’s nutritional strategy involves the complex interplay between its dynamic physiology and its environment, an environment that includes a landscape of foods that vary in nutritional composition as well as a social environment of other feeding individuals. Social behavior—cooperative or competitive, with conspecifics or with other sympatric species—influences individual feeding behavior. Investigation of social feeding by estimating individual intake of multiple nutritional components, sometimes referred to as “social nutrition,” can give insight into how social variables may lead to shifts in nutritional niche.
In this study, I examined the effects of temporal shifts in diet, reproductive status and conspecific and heterospecific social factors on the nutritional intake of an arboreal guenon. This study draws from 137 full-day focal follows of adult female redtail monkeys (Cercopithecus ascanius) in three study groups in Kibale National Park, Uganda; phenological data from the monkey group home ranges; insect abundance data via malaise trap and sweep net methods; nutritional wet chemistry or near-infrared reflectance spectroscopy analyses of over 600 food samples; and mineral analyses via inductively coupled plasma optical emission spectroscopy of 101 food samples.
I first characterized the redtail nutritional strategy as it relates to fruit in the diet, monkey group and reproductive status. I found that redtail monkeys are “food composition generalists,” consuming food items that are diverse in macronutrient and mineral composition. Insects were modest contributors to metabolizable energy and protein in the redtail diet, given that time spent feeding on insects was comparable to fruits, but insects contributed substantially to mineral intake. The balance of dietary nonprotein energy to available protein (NPE:AP) of redtail females was similar to other omnivorous primates. Redtail female nutritional strategy with respect to NPE:AP was affected by habitat variation in their home ranges, while ripe fruit in the diet or reproductive status did not have a strong effect on nutrition. One redtail group relied on the fruit and gum of Prunus africana, a high density tree in disturbed areas, which led to higher dietary NPE:AP than the other groups. Increased switching among foods was associated with increased sodium, copper and iron intake, suggesting that diet diversity and rapid food switching enable increased consumption of minerals.
Second, I examined the relationship between redtail female agonism and nutritional strategy. Redtail monkey females exhibited low levels of within-group female agonism compared to other cercopithecines. Intragroup agonism was mostly in a feeding context, suggesting that some intragroup contest competition occurs. A relationship between agonism during feeding and daily nutritional intake could not be detected for multiple macronutrients and energy. Foods that female redtail monkeys contested over were diverse in food type and in macronutrient and mineral composition. Third, I examined how polyspecific association affects female redtail daily nutritional intake. The redtail study groups varied in polyspecific association patterns and partners. I could not detect a relationship between polyspecific association with blue monkeys (Cercopithecus mitis) or grey-cheeked mangabeys (Lophocebus albigena) and redtail daily food intake, total metabolizable energy, nonprotein energy, sodium, or copper, regardless of shifts in dietary ripe fruit. An established interspecific dominance hierarchy by body size at feeding trees leading to spatial adjustments and mitigating interspecific competition may help explain this result. Food over which redtails and heterospecifics contested did not fit one nutritional profile and were instead diverse in macronutrient and mineral composition.
Redtail monkeys combine foods of diverse nutritional composition and use fat, digestible fiber and nonstructural carbohydrates interchangeably as energy sources. This study characterizes the diet of a generalist forest guenon, clarifies the mineral-driven role that insects play in the redtail monkey diet, and suggests that redtail females may suffer minimal daily nutritional costs of intragroup agonism and of polyspecific association.
Bryer, Margaret, "Nutritional Strategy and Social Environment in Redtail Monkeys (Cercopithecus ascanius)" (2020). CUNY Academic Works.