Animal of the Issue: Orangutans

At the National Zoo in Washington, D.C., there are high wires that allow the orangutans to move freely between enclosures. Photo Credit / Lian Mlodzienski
At the National Zoo in Washington, D.C., there are high wires that allow the orangutans to move freely between enclosures. Photo Credit / Lian Mlodzienski

At the National Zoo in Washington, D.C., there are high wires that allow the orangutans to move freely between enclosures.
Photo Credit / Lian Mlodzienski

By Lian Mlodzienski
Science Editor

The Orangutan, Pongo pygmaeus (Bornean) and Pongo abelii (Sumatran), is the world’s largest tree-dwelling animal.

The Bornean species is usually stockier and darker than the Sumatran species. The Sumatran species is characterized by its longer hair and more pronounced beard.

The name Orangutan stems from the Indonesian and Malay languages. “Orang-utan” translates to “person of the forest.”

This species can be identified by its orange to red hair and long arms with curved hands and feet. This adaptation allows them to travel easily on wires or swinging from tree tops. Some adult orangutans have arm spans that measure over seven feet from fingertip to fingertip.

Within the species, there are some distinctions between male and female orangutans. Males tend to have longer hair and are twice as large as females. They can stand about four and a half feet tall and weigh 130 to 200 pounds.

In comparison, females may stand about four feet tall and weigh only 90 to 110 pounds. Some males may develop disc-like cheek pads and exhibit bimaturism.

This means that there are two versions of the adult male. While the two morphs are similar, they differ in whether or not they have highly developed throat sacs and large, disc-like cheek pads.

All orangutans have these pouches through which they make their calls for communication; males have the more developed pouches.

Both genders have powerful teeth and jaws that they use to crush the foliage and hard-shelled nuts that they eat. Their diet consists mostly of fruit. This diet can be supplemented with other vegetation, invertebrates, mineral-rich soil, and sometimes small vertebrates.

This diet is sustained by their natural habitat in tropical rainforests. This includes a variety of swamps, mature riparian, lowland dipterocarp, and hill dipterocarp forests. It is in these areas that males establish their home range.

The home range of the average orangutan can incorporate several females. At around twelve years of age, females reach maturity and remain fertile for over thirty years.

Of all of the land-living animals, orangutans have the longest inter-birth interval. Young orangutans may stay close to their mothers until the next offspring and may nurse until the age of 6.

The orangutan spends its day high in the trees and is the most solitary of the great apes. In times of fruit abundance, the animals are more social. They have a working map in their memory of the fruiting trees which they may revisit. If they find a tree with an abundance of fruit, they may spend hours feeding.

At night, the orangutans make nests out of bent branches. These nests can be made new at night or reused and added to each day.

Did you know that:

  • Orangutans have 32 teeth. The same number of teeth are found in the human mouth!
  • It is believed by some people that the Great Apes and Humans share a common ancestor who lived between 12 million and 15 million years ago.
  • Orangutans are believed to be seven times as strong as a human.
  • In one day, an orangutan may travel from 50 meters to 1,000 meters.

Email Lian at:
lmlodzien1@live.esu.edu

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