This means that in a female's reproductive life time she may only produce three or four offspring. The youngster is solely dependent on its mother until her next baby is born. Compared with other apes, orang-utans are fairly unsociable creatures and the only real bond that is formed is between mother and offspring. The young stay with their mother until adolescence at about the age of seven, but after that they generally only see each other from time to time. The males move away in search of their own territories.
Males travel long distances, paying little attention to other orang-utans that they meet.
When the males become sexually mature they develop many distinctive physical features that are very characteristic of orang-utans. Fleshy cheek pads form on both sides of their face and a high, fatty crown on their head. Their hair grows long and a beard develops on their faces. The call is thought to be a mating call, but little is known yet about its exact purpose. One of the most outstanding features of orang-utans is their ability not only to remember where all the desirable fruit trees are, but to know exactly when each fruit type will be at its ripest.