As with colobines, the gases serve as the energy source. Unlike colobines, howler monkeys do not have the sacculated stomach, but rather a simple acid stomach that also contains two enlarged sections in the cecum and colon in which fermentative bacteria are found. colobus monkeys) receive energy rich gases from the bacteria triggered reaction (fermentation). Instead, with the help of bacteria contained in a sacculated stomach, all monkeys in the subfamily Colobinae (e.g.
Mammals do not have the enzymes capable of digesting cellulose, the carbohydrate that composes the leaf cell wall.
These tree-dwelling herbivores mainly consume tree and vine leaves, flowers and tropical forest fruits.
