Size
Orangutans are the world's largest arboreal (tree-dwelling) mammals.
Adult males weigh between 50 to 90 kg (110 to 198 lb.) and can stand between 1.25 to 1.5 m (4.1-5 ft.) in height.
Adult females weigh between 30 to 50 kg (66 to 110 lb.) and stand about one m (3.3 ft.) in height.
Hair & Coloration
Orangutan coloration can vary greatly between dark-brown and pale reddish-orange but is most often reddish-orange in color. Refer to Taxonomy—Species for species specific coloration.
Orangutan hair is thin and shaggy.
Shoulders & Arms
Orangutan arms are one and a half times longer than their legs. When stretched out to the sides, an adult male orangutan’s arms may measure 213 cm (7 ft.) in length. Their strong arm muscles enable them to swing from tree to tree and, along with its shoulders, support the weight of their body.
Although not as strong as a gorilla, an orangutan is about seven times stronger than a human.
Since orangutans primarily move through the forest using their arms and shoulders as opposed to their legs and hips, their arms are longer than their legs and their shoulders are wider than their hips.
Cheek Pads
Sexually mature male orangutans have cheek pads that are composed of subcutaneous (underneath the skin) accumulations of fibrous tissue. These pads are located between the eyes and ears and have a similar appearance to a horse with blinders on.
Cheek pads are thought to help extend the range of their vocalizations by channeling the sounds directly similar to a megaphone.
In addition to their massive size, cheek pads enhance adult male orangutans' visual impact, making their threats more convincing.
Throat Sacs
Both males and females have a hanging sac from their throats. As males mature, their throat sacs become much larger. The throat sacs are inflated to make their vocalizations carry further. Some male vocalizations have been documented to carry up to 80 m (a half mile) in distance.
Mouth
In addition to eating, orangutans will carry large objects in their mouths while keeping their hands and feet free for traveling.
Orangutans have powerful jaws capable of cracking, crushing, and chewing fibrous foods such as fruit with spiny coverings, nuts, and tree bark.
Orangutans use their lips to detect food textures before biting into them and to exaggerate facial expressions used in communication.
Hands & Feet
Orangutan fingers and toes are long and curved to help hold and quickly release branches as they traverse the treetops.
The thumb and big toe of orangutans oppose the other digits (fingers/ toes), enabling them to grasp and manipulate objects. The opposable thumbs and big toes are small in size so they do not hinder swinging through the forest.
Orangutan feet are adapted for climbing trees. Their feet grasp branches and serve as an extra support, in addition to their hands, when hanging upside-down.
Orangutans can hold, eat, and manipulate food using their hands or just their feet. This agility allows them to even place a foot in their mouth while hanging from a branch.
All primates have individualized fingerprints and toeprints, which may be used for identification purposes in the field.
Primates have fingernails and toenails rather than claws. They are used for opening, scraping, cleaning, and scratching.
Hips & Legs
The hips of orangutans are highly mobile. They have full rotation of their joints, allowing their legs to move at almost any angle. Humans have this extensive range of rotation only in the shoulder joints, allowing the arms to move freely.
The legs of orangutans are smaller than their arms because they are not primarily used in swinging and do not support their body weight.
Orangutans have flexible knee and ankle joints, enabling them to jump, twist, grip and balance as they swing from branch to branch.
Tails
Orangutans, like other apes, do not have tails.
Brain
The cerebellum is the part of the brain that controls posture and movement. Apes have larger cerebellums than humans, a trait that probably reflects the demands of an arboreal, tree-dwelling lifestyle.
Dentition
Orangutans have 32 teeth, the same number as humans.
