Description and biology

The only great ape found in Asia, the orangutan is the largest living arboreal (tree–dwelling) ape. In the Malay language, its name means “forest person” or “man of the woods.” With its long, powerful arms and hands and feet that can grasp branches, the animal moves easily from tree to tree.

The orangutan’s reddish brown coat is long and soft. It has small ears, a bulging snout, and a high forehead. An average orangutan has a head and body length of 30 to 40 inches (76 to 102 centimeters) and a shoulder height of 45 to 60 inches (114 to 152 centimeters). It weighs between 85 and 220 pounds (39 and 100 kilograms). Males are much larger and heavier than females.

Orangutans spend 95 percent of their lives in trees. During the day, the animals feed primarily on fruit. They also eat leaves, insects, bark, and young birds and squirrels. Each night, they build a nest in a tree 35 to 80 feet (11 to 24 meters) above the ground. Their home range varies from 1 to 4 square miles (2.5 to 10 square kilometers).

The orangutan is a solitary animal. The only bond formed is between a mother and her infant. Mating, which can occur at any time during the year, is the only time males and females interact. They stay together for a few days to a few months until the female is pregnant, then they split up.

After a gestation (pregnancy) period of 233 to 270 days, a female gives birth to one young. She raises the infant alone, keeping it constantly with her for the first year. She nurses the infant for up to three years. During a normal life span of 40 years, a female will bear only 4 or 5 offspring.

Habitat and current distribution

The orangutan inhabits a variety of forest habitats, including swampy coastal forests, mangrove forests, and mountain forests. It is found only on the Southeast Asian islands of Sumatra (part of the country of Indonesia) and Borneo (divided among Malaysia, Indonesia, and Brunei).

In the mid–1990s, biologists (people who study living organisms) estimated that 12,000 to 20,000 orangutans existed on Borneo, while another 9,000 lived on Sumatra.

History and conservation measures

For thousands of years, the orangutan has been a victim of human abuse. Early humans considered it a food source and hunted it to the point of extinction in many areas. Orangutans once ranged throughout Southeast Asia. They now live on only 2 percent of that original range.

The greatest threat to orangutans is habitat destruction. The relentless clearing of rain forests to create plantations on the islands has reduced their habitat by 90 percent in the last 50 years.

The animals are driven into forest areas that are too small to support them. Seeking food, the orangutans often wander onto nearby plantations. They are then killed or injured by workers protecting the crops.

In late 1997, orangutans and other wildlife in Southeast Asia suffered terribly from devastating wildfires and smoke that swept across the region. The fires resulted from man made and natural causes. Farmers in the region rely on slash–and–burn agriculture, a process whereby a forest is cut down and all trees and vegetation are burned to create cleared land.

When the El Niño weather pattern delayed the seasonal monsoon rains, hot and dry conditions fanned the fires. Many orangutans died in the fires or from smoke inhalation. Others were killed by frightened villagers as they escaped the burning forests.

In 2000, the Indonesian news agency announced that the population of orangutan in Indonesia had dropped by one–third in the three years after the fires, noting that the animals had still not recovered. Individual orangutans were still found wandering outside their former habitat.

Another major threat to orangutans is capture. Thousands of females have been slaughtered so their offspring could be captured and sold as pets. Some childless couples even raise the animals as children, dressing them in human clothes.

In the late 1980s and early 1990s, the demand for orangutan pets was especially strong in Taiwan, where a children’s television show featured a pet orangutan. Of those infants that are captured in the wild, up to 50 percent die during transport.

Several protected reserves have been established in the orangutan’s range, including the Gunung Lueser National Park in northern Sumatra and the Tanjung Puting National Park in Borneo.

Conservationists and wildlife researchers have also established camps to help train orangutans that were once pets to return to their natural habitat. However, most of these orangutans have spent too much time among humans and cannot exist in the wild.

In 2002, there was some good news. An expedition into the remote wilds of Borneo discovered a large and previously unknown population of the species, comprising perhaps the largest remaining orangutan population. But as clearing of the forests continues at a rapid rate, this population, too, is in jeopardy.