Sumatran orangutans are the largest non-human primates in Asia and the largest arboreal primates. They have long, fine red hair on their bodies and faces. Males have large cheek pads that are covered in a fine white hairs.The arm span, from finger tip to finger tip, is 2.25 m. The legs are small and weak compared to their muscular arms. There is sexual dimorphism between males and females. Female weights range from 30 to 50 kg and they can reach 1.3 m tall. Male weights range from 50 to 90 kg and reach a height of 1.8 m. Some old males may get too large to move around in trees easily and may have to resort to walking on the ground.
Sumatran orangutans may be distinguished from Bornean orangutans (Pongo pygmaeus) by their longer fur, more slender build, white hairs on the face and groin, and long beards on both males and females, but molecular characters are considered most definitive.
Range mass: 30 to 90 kg.
Range length: 1.3 to 1.8 m.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; sexes shaped differently; ornamentation