The lifespan of orangutans is 35 to 40 years in the wild and up to 60 years in captivity.
Female orangutans will not have their first offspring until 15 to 16 years of age. Males may attain sexual maturity in their teens, but their flanges [large cheek pads] may not become fully-developed until they are in their twenties in Borneo and thirties in Sumatra. Males without flanges are less successful in attracting sexually receptive females than fully mature males with flanges.
Orangutans have a reproductive cycle that is similar to humans. The female’s menstrual cycle is 29 to 32 days, with menstruation lasting three to four days. The gestation period is approximately eight and a half months. Usually a single offspring is born, and this occurs every 6 to 7 years.
Juvenile orangutans are 1.5 to 2 kg at birth. The young stay close to their mother until they reach adolescence. Orangutans have the longest ‘infancy’ of the great apes. Often females carry their young up to the age of five years when crossing the canopy from tree to tree.
Orangutans reproduce very slowly. This results in fierce competition for males to find females. Also, females are selective in the mating process. The main consequence of this is that it can take decades to replace population losses.