The word colobus is derived from a Greek word meaning "mutilated."  This name was given to the colobus monkey because of its stunted or non-existent thumb, which appears to be mutilated.  The lack of such a thumb is said to be an advantage for this arboreal species because it allows them to swing through trees without getting it caught in branches.  The colobus monkey ranges in size depending on variety from.  The olive colobus monkey, about 4 kg, and the red colobus monkey, about 8.2 kg, show little sexual dimorphism.  Black-and-white colobus monkeys and the black colobus monkey exhibit sexual dimorphism.  Black-and-white colobus monkeys range in size from 6-14.5 kg and black colobus monkeys range in size from 6-11.5 kg, with males being considerably larger.

The black colobus, red colobus and olive colobus live in overlapping home ranges, whereas black-and-white colobus often live on classical territories.  The reason for this difference is primarily resource dispersion.  The black, red and olive colobus tend to live in areas of superabundant food, making a territory unnecessary to defend.  Black-and-white colobus monkeys living in areas with narrow, riparian forests, prolonged dry seasons and food that is distributed in a way that is defensible live on territories, while those who may live in areas of greater food abundance will live on home ranges.