Black and white colobus monkeys belong to the subfamily Colobinae, they are found across equatorial Africa.Females give birth to an average of one offspring every 20 months. Infants are born with eyes open, Offspring are born with “natal fur” which is fluffy and white. They live in groups of three to 15 individuals. Groups are made up of one adult male (rarely two) and females with offspring. Females’ troop membership is stable but males must earn their status. Young males are forced by the lead male to leave their natal troop before breeding age. Lead males are occasionally ousted by young mature males that grew up with them or moved in from an outside troop. Guerezas defend their ranges vigorously. Males do most of the defending by displaying through the trees with leaps and roars which can be heard a mile (1.6 km) away. The name “colobus” is derived from the Greek word meaning “docked” or “mutilated.” Colobus monkeys once were thought to be abnormal because they have no thumb, or only a small stub where the thumb would usually be. This is actually an adaptation rather than a mutilation which allows colobus monkeys to easily travel along the tops of branches quadripedally. Colobus monkeys have unusual stomachs which are similar to the digestive systems of cows. Colobus monkeys always have a belly full of food which is in the process of being digested. The contents of the stomach can constitute up to a quarter of the weight of an adult and half the weight of an infant monkey.