The eastern red colobus has a blackish back and tail and buff underparts, and a red crown to its head. In Gombe, they live in troops of 30-80 individuals, with numerous males. Red Colobus monkey Colobus are specialized leaf-eaters. Leaves are very nutritious, but most animals cannot digest their cellulose cell walls. Colobus have solved this problem in the same way as many hoofed animals, by evolving a four-chambered stomach where bacterial fermentation breaks down the cellulose and releases the nutrients.
Red colobus are also very selective, and choose the tenderest, most nutritious parts of trees.
Since new leaves, flowers etc. are only briefly available in any one place, a colobus troop must range widely. A troop of 80 studied at Gombe had a range of about 1.1 sq km. That is 24 times as big as ranges recorded for redtails and blues. Usually they eat in the morning and evening, and in the dry season they also feed at midday. Colobus are sometimes seen feeding in the same trees as redtail and blue monkeys, but their diet does not overlap much with that of any other primate species in the Park.