Orangutans (Genus: Pongo) are the largest living arboreal (tree-dwelling) apes in the world. Extremely limited in habitat, orangutans can only be found in rainforests on the islands of Sumatra and Borneo. They are distinctive in that they do not have tails like smaller arboreal apes and they have reddish-brown hair instead of the brown or black hair of most apes.
Orangutans are quite large, with most standing 4-5 feet tall and weighing 73-180lbs. Males tend to be somewhat larger than females and can at times weigh well in excess of 200lbs. Orangutans have strong arms that are more than twice the length of their legs, with some having wingspans of over 7 feet. They have both opposable thumbs and opposable big toes, making it possible for them to grip items with their hands and their feet. The orangutan’s head is large in comparison with its body and mature males will develop what are known as cheek flaps, which are used as a sign of dominance and grow larger as the ape ages.
Orangutans spend the majority of their time in trees of old forests; though will occasionally enter grasslands and gardens. The bulk of the orangutan’s diet is fruit such as figs, however it is known that they will also consume vegetation, insects, honey and eggs, and will vary their diet based upon availability. Orangutans are quite skilled at making tools and will use simple devices to aid in building, as well as extracting seeds and insects when feeding.
While they are social animals, orangutans are more independent than most apes. Their social structure is comprised of both resident males and females who maintain a defined home range, and transients of both sexes that travel frequently, usually before finding a mate and establishing a range of their own. The range of a resident male will usually overlap that of several resident females with whom he will breed. Outside of breeding and occasional socializing, only mothers and their offspring develop any long term bonds.
Once a mature male has established a range of his own he will attempt to mate by making long calls advertising his location to females. After mating, the male may choose to stay around the female for some time, but will leave long before any offspring are born. After a 9 month pregnancy the female will give birth to her young. The baby will be completely dependent on her for the first two years of life and will never even break physical contact with its mother for the first four months of life. Female orangutans reach maturity at 6-11 years of age, with males doing so at 15 years. The average lifespan for orangutans in the wild is 35 years, with some in captivity reaching 60 years.
- Captive orangutans have shown the ability to understand how nuts and bolts work, and how to stick pegs in correctly-shaped holes.
- Orangutans have been known to steal moored boats by untying them and using them to cross rivers.
Smithsonian National Zoological Park
San Diego Zoo