Differences Between Males and Females
Orangutans are a sexually dimorphic species. This means that there are big differences in the size and shape of male and female orangutans! A very noticeable difference seen between male and female orangutans is their body size. Male orangutans can weigh over 200 pounds (90 kg), while females are ⅓ to ½ of their size. Due to their large size, males will usually travel on the ground more so than females.
One of the most noticeable differences between male and female orangutans is their facial morphology, or the structural differences in how their faces look. Male orangutans have two stages of development or growth. The first stage is called “sub-adult male” and the other is called “fully adult male”. Sub-adult male orangutans are usually thinner and do not have the long, thick hair that the fully adult males usually have. The sub-adult male orangutans also do not have cheek pads or flanges, which is referred to as being unflanged.
Along with the lack of cheek pads, sub-adult males do not have an overly large throat sac, which they use to make a specific “call” that echoes through the forest. This call is called a “Long Call” and is used to both locate and attract female orangutans and scare other males away.
This video below is of a flanged adult Bornean orangutan named Chaz making a long call.
Video Courtesy of the Tuanan Research Station, Central
Male orangutans will usually stay alone until they find a female who is willing to mate with them. The male will stay with the female orangutan for several days to make sure the mating was successful. After these days, the male orangutans will return to their solitary life.