Quantifying Mineral Intake and the Role of Minerals on Food Selection in Angola Black and White Colobus Monkeys (Colobus angolensis palliatus)

Minerals are vital for many metabolic processes, and mineral deficiencies can adversely impact health and fitness. Mineral concentrations of food items are commonly reported in primate nutritional ecology studies and have been identified as important factors in primate food selection; however, very few studies have quantified daily mineral intake of free-ranging primates. We examined the concentration of 9 minerals (Ca, P, Mg, K, Na, Fe, Zn, Cu, and Mn) in foods consumed by Colobus angolensis palliatus inhabiting the Diani Forest of Kenya, and test whether individuals preferentially selected leaves in accordance with their mineral concentrations. We also examined the effects of sex, group, and season on daily mineral intake, quantifying both percentage-based and mass-based intakes. We then compared daily mineral intake values to published recommendations. Behavioral data and plant samples were collected from July 2014 to December 2015. We found that individuals preferred leaves with greater P content and lower Ca content. Daily mineral intake differed significantly between sexes and among groups and seasons. These results are interpretable via differences in time spent feeding and total energy intake. Intakes fell below percentage-based recommendations for P, Na, Fe, Cu, and Mn but met or exceeded mass-based recommendations for all minerals except Na. This discrepancy is likely explained by the conservative nature of percentage-based mineral recommendations and the difficulty of comparing and scaling mass-based mineral recommendations among primate species. Studies that quantify daily mineral intake are needed to better understand the role of minerals on dietary selection, more accurately identify potential mineral deficiencies, and provide more informed recommendations for captive primates.