Classification and Range
Orangutans (oh-RANG-uh-tans) belong to the family Hominidae, which includes all four great apes: gorillas, chimpanzees, bonobos and orangutans. Distinct species of orangutans live on the islands of Borneo and Sumatra in Southeast Asia.
Tropical and subtropical moist broadleaf forests. Lower densities in mountainous areas.
Males up to 5 feet (1.6 m)
Females up to 3.5 feet (1 m)
Males 155-200 pounds (70-90 kg)
Females 65-110 pounds (30-50 kg)
The median life expectancy for orangutans is 28 years.
In the wild: predominantly fruit (figs, durian, mangoes, etc.), leaves, flowers, bark, occasional bird eggs, insects and mineral-rich soil.
At the zoo: Lettuce, celery, broccoli, spinach, kale, high-fiber biscuits, apples, oranges, bananas and other tropical fruits, and fresh browse when available.
Females become sexually mature at around ages 7 or 8 and typically will only reproduce about 2 to 3 offspring in their lifetime. Males become sexually mature around the age of 13 to 15 years. Recently it has been discovered that sub-adult males, as well as adult male orangutans, have also successful been able to sire young.
Gestation period is about eight to nine months. Females usually bear single young; twins are rare. Average birth weight is 3.5 pounds (1.6 kg). In the wild, sexually mature females only give birth every 5 to 9 years, depending on the environmental conditions and food availability.
Young orangutans are dependent on their mothers for survival during the first five years of their lives. Since young orangutans have few instinctive behaviors, they must learn from watching their mothers. Between 3 and 7 years, orangutans become increasingly independent, and leave their mothers by ages 5 to 8.
Orangutan - People of the Forest
In the Malay and Indonesian language, orang means "people" and hutan "forest," thus orangutan literally means "people of the forest." Highly intelligent, orangutans have long, coarse hair ranging in color from bright orange to maroon or dark chocolate. Mature male orangutans develop massive cheek pads and large throat pouches. Males inflate their pouches to make loud vocalizations referred to as "long calls."
Rarely descending from trees, orangutans have nearly identical hook-shaped hands and feet that are well adapted for grasping and hanging from tree limbs. Young orangutans easily swing from limb to limb. Older, heavier adults must move through the forest slowly, using their hands and feet to test each branch to see if it will hold their weight. When required, however, an adult orangutan can move very fast. Orangutans have long, strong arms and relatively short legs, which is an excellent adaptation for locomoting from tree to tree.
Social Organization - The Solitary Life
Unlike gorillas, chimpanzees and bonobos who live in large male/female social groups, male orangutans are mostly solitary animals. Females may live in small groups composed of dependent young, other adult females and adolescents. The load-bearing limits of rain forest tree tops, combined with the scarcity of fruit, keep orangutans from living in large social groups.
During courtship and mating, however, adult male and female orangutans travel and forage together. The long call of a dominant male, audible for up to a mile (1.6 km), announces his presence to females who are ready to mate. The call also scares away other, less dominant males. Females seek out the male to breed, but after a few days they separate and return to their solitary life.
Location at the Zoo
Woodland Park Zoo's orangutan forest, located at the Trail of Vines exhibit in Tropical Asia, brings visitors eye-to-eye with orangutans in their treetop habitat. Visitors have an unobstructed view to observe orangutans as they may behave in the wild. The exhibit also has an indoor area for up-close viewing of the orangutans.
Orangutans are an endangered species. Overpopulation, logging, agriculture, conversion of forests to oil palm plantations, and other human activities are rapidly destroying forest environments required by orangutans for survival. While population densities are difficult to determine, estimates for the Bornean species are 54,000 while the critically endangered Sumatran species has dwindled to a mere 6,600 animals.
Woodland Park Zoo is involved in orangutan research and conservation in the wild. Zoo staff traveled throughout Indonesia doing tissue sampling of wild and captive orangutans. This study confirmed that the two orangutan subspecies are very different genetically, and should be managed separately and not allowed to interbreed. While the zoo's resident orangutans are hybrids (crossbred between Bornean and Sumatran species), and therefore are not allowed to reproduce, these animals play a critical role in educating zoo professionals and the public about the amazing orangutan. As an example, the first orangutan in vitro fertilization was accomplished at Woodland Park Zoo. Although no offspring resulted, it was an important step in the continuing development of embryo transfer techniques.
How You Can Help!
You can help preserve and protect wildlife and their habitat. Join and become active in Woodland Park Zoo and other conservation organizations of your choice. Please do not buy products made from wild animal parts.
Contact Woodland Park Zoo at firstname.lastname@example.org find out other ways you can support conservation programs at the zoo. Discover more about endangered orangutans by visting the Orangutan Conservancy website.
Sources and Suggested Reading
Russon, Anne. 2004. Orangutans: Wizards of the Rainforest. Firefly Books. 240p.
Can Shaik, Carel. 2004. Among Orangutans: Red Apes and the Rise of Human Culture. Belknap Press of Harvard University Press. 256 p.
Wich, Serge, et al. 2009. Orangutans: Geographical Variation in Behavioral Ecology and Conservation. Oxford University Press, USA. 464p.
Shumaker, Robert. 2007. Orangutans. Voyageur Press. 72p.
Smith, Dale. 2001. What the Orangutan Told Alice. Deer Creek Publishing. 192p.
Zoo Books. 1996. Orangutans. Wildlife Education Ltd., San Diego, CA. 21 p.