It is the largest arboreal mammal. The body is short and stocky, the arms are long and the legs are short. The feet and hands are similar, with long, hooked fingers to move more easily through the trees. They swing from branch to branch, always holding on with two limbs until they reach the next support. They barely descend to the ground, where they become clumsy and vulnerable. They are endowed with great intelligence, and sometimes use tools to obtain food. They are animals with solitary habits.

Females are fertile at 15 years old and the young usually remain with their mother until they are 8 years old, so they do not usually have more than 4 or 5 young.

Dominant males are distinguished by a marked mask located on their cheeks. This mask begins to develop at approximately 12 years of age. If there is a dominant male nearby, the growth of the mask will be delayed until 18-20 years of age and will be smaller in size.