Although gibbons are apes, they are known as lesser, or small, apes. They can reach 18–25 inches in height and weigh up to 12.5 pounds. They have extremely long arms and legs.
Gibbons are unique in that infants are born with blonde fur like their mother, but by age 2 their color turns to black. When they reach adulthood, males remain black and females change back to blonde.