They also have large salivary glands and a large stomach that is divided into compartments. Such specialized structures help leaf-eating monkeys digest their coarse food. Unlike other Old World monkeys, leaf-eating monkeys do not have cheek pouches. Most kinds of monkeys give birth to one baby at a time. But marmosets and tamarins sometimes produce twins or even triplets.
Most baby monkeys depend completely on their mother for food and security.
They nurse on her milk for a few weeks to two years, depending on the species. A baby monkey hangs onto its mother almost from the moment of birth by grasping her fur. The mother carries the infant until it can travel safely on its own. At first, the infant clings to its mother's underside. Later, the young monkey rides on its mother's back.