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Orangutan

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Orangutan

Order: Primates
Family: Pongidae
Genus and Species: Pongo pygmaeus (Bornean) and Pongo abelii (Sumatran)

The world's largest tree-dwelling animal, the orangutan relies upon its intelligence and well-adapted body to survive in the tropical rainforest.

Physical Description

These orangish-red-haired great apes have long arms and curved hands and feet, which they put to good use when traversing the treetops. Males tend to have longer hair than females and are about two times larger than females. Some males develop disc-like cheek pads. Male orangutans exhibit bimaturism, existing in two adult male morphs: flanged and unflanged. Flanged males have highly developed throat sacs and large, disc-like cheek pads.

Both sexes have throat pouches that make their calls resonate through the forest. The males' pouches are more developed. Orangutans crush tough foliage and hard-shelled nuts with their strong teeth and jaws. Two species exist: P. pygmaeus of Borneo, and the Sumatran species, P. abelii. Bornean orangutans are typically darker and stockier than Sumatran orangutans, which tend to have longer hair with more pronounced beards.

Size

Orangutans are Asia's largest primates, and males are larger than females. Males stand about four and a half feet tall and weigh 130 to 200 pounds. Females stand about four feet tall and weigh 90 to 110 pounds.

Geographic Distribution

Once more widely distributed, orangutans now live only in forests on the Southeast Asian islands of Sumatra and Borneo.

Status

The Sumatran species is listed as Critically Endangered and the Bornean species is listed as Endangered on the World Conservation Union's Red List of Threatened Animals.

Habitat

Orangutans live in tropical rainforests, including mature riparian, freshwater swamp, peat swamp, lowland dipterocarp, and hill dipterocarp forests.

Natural Diet

Orangutans feed primarily on fruit, supplemented with leaves, flowers, non-leafy vegetation, invertebrates, mineral-rich soil, and occasionally small vertebrates. In El Nino years, droughts on Borneo create periods of food scarcity that result in prolonged reliance on “fallback goods”, particularly the inner bark of trees.

Reproduction

Male orangutans establish home ranges that embrace those of several females. Females reach maturity at around twelve years of age and can remain fertile for more than 30 years. Sumatran orangutans have inter-birth intervals (the time between consecutive offspring) of up to 8-9 years. Young orangutans may nurse until at least age six, and stay close to their mothers until the next offspring comes along.

Life Span

Orangutans may live into their 50s both in the wild and in zoos

Behavior

Active during the day and primary arboreal, orangutans spend most of their lives high in the trees. Orangutans are the most solitary of the great apes, but are highly social especially in times of fruit abundance. Each night, orangutans bend branches into nests, most often making a new nest but sometimes re-using or adding to an older nest. Nests that support the apes while they sleep in the trees and are also frequently made during the day.

Orangutans move slowly through the forest, seeking fruiting trees, which they may find by following the movements of hornbills and other fruit-eaters, though orangutans are also known to have cognitive maps of the fruiting trees that the revisit. When heavily fruiting trees are found, orangutans will spend many hours feeding at a single feeding site.

Past/Present/Future

Once widespread in Asian tropical forests, orangutans now live only on Sumatra and Borneo, where forest loss due primarily to illegal logging and the expansion of non-sustainably grown oil palm plantations is the greatest threat to their existence. The destruction spreads even further during dry years. In 1997, an area the size of New Jersey burned in Indonesia, and many of the fires occurred in orangutan habitat.

A Few Orangutan Neighbors:

Proboscis Monkey (Nasalis larvatus): A large vegetarian that lives in forests near water only on Borneo. Males are twice the size of females and have bulbous noses.

Asian Small-Clawed Otter (Amblonyx cinerea): This small, social otter frequents streams and swamp forests, where it eats crabs and other small animals.

White-Crowned Hornbill (Aceros comatus): One of five species of large, long-billed fruit-eating birds that share forests with orangutans on Sumatra and Borneo.

By saving orangutan habitat, we protect these and many other animals.

Fun Facts:

In the Indonesian and Malay languages, "orang- utan" means "person of the forest."

An adult orangutan's arms can be well over seven feet from fingertip to fingertip.

Orangutans have the longest inter-birth interval of any land-living animal.