The gestation period of female Orangutans is very similar to humans lasting slightly less than 9 months. Also in this similarity is the female menstrual cycle.  The Orangutan cycle occurs every 29-32 days, menstruation lasting 3-4 days.  Usually a single young is born at a time, weighing approximately 3-1/2 lbs. The young stay with or close to the mother until they are mature. Females become sexually mature when fully grown, at about 12, although they will not have their first offspring until 14 to 16. Males attain sexual maturity and full growth at 15 but the Borneo cheek pads may not become fully developed before 20.   Males are not successful in attracting sexually receptive females until they receive their cheek pads.  It is noted that the presence of a dominant cheek-padded male within the sensory range of a younger adult male inhibits cheek-pad development.   The life cycle of an Orangutan passes through infancy (0-4 yrs.), juvenile (4-7 yrs.) and adolescent (7-10 (males) or 12 (female) yrs.) stages.  Life expectancy of orangutans in the wild is unknown but estimated at thirty to forty years.  Orangutans in captivity have been known to live upwards of fifty plus years under excellent conditions.

     The diet of the Orangutan consists primarily of fruit, leaves, bark, flowers, insects, and birds eggs. One of their preferred foods is the fruit of the durian tree, which tastes somewhat like sweet, cheesy garlic custard. They discard the skin, eat the flesh and swallow the seeds. Their diet also consists mainly of fruit, especially figs. Various species of figs ripen at different times in the year, and the movement pattern of the animals can largely be explained by their following this process.  Fruit seeds are often deposited into feces to grow into fruit bearing trees in another part of the forest.  Orangutans are important seed disperses for many species of tropical fruit trees.  They drink by reaching into tree holes and lapping water from their hands. 

     Orangutans have a vocal repertoire of about 13 sounds. Within a small social group they communicate with lip smacking. They scream when scared, and males sometimes roar. They seem to grind their teeth when frustrated. Males also emit a long series of loud groans, which can be heard by a human up to 1 kilometer away. This vocalization may serve to space males apart.

     Like the other great apes (chimpanzees and gorillas), orangutans are highly intelligent. Tests indicated that their intelligence is relatively similar among the species. The native intelligence of orangutans is used to solve problems related to arboreal travel and food processing. In captivity, they have been trained to perform tricks and communicate with sign language to ask for items of interest, such as food and contact.