Colobus monkeys are unique among the primates as they are primarily folivores and digest fibrous foods through foregut fermentation. Although they mainly eat leaves, they also consume seeds, fruits and grasses in some locales. They navigate a complex nutritional landscape as a result of the environments they are faced with. To understand their nutritional ecology we explore the foods that colobines eat, the nutrient compositions of their diets, how they select foods and their interactions with toxins.