Sexual Dimorphism in Non-Human Primates

By-Shannon Garnett

Everyone knows that humans are sexually dimorphic, in fact, we see it every single day; but have you ever thought about how other primates are sexually dimorphic? Are they sexually dimorphic in the same way? I did some research on chimpanzees, gorillas, orangutans, gibbons, old world moneys, new world moneys, tarsiers, and lemurs to answer this question and this is what I found.

Chimpanzees are mainly dimorphic in just size. The common female weighs between 57-100 pounds and the male weighs between 90-115 pounds.

http://michaelkeenan.net/images/gorilla_couple

Gorillas are highly sexually dimorphic. Males weigh about 350 pounds and females usually reach around 155 pounds. They also differ in their facial features. Males have a more a more protruding sagittal crests, brow line and canine teeth then females. Male silver-backed gorillas grow a sheet of white hairs on his backs and females do not.

Orangutans are also highly sexually dimorphic. Their faces are mostly hairless however, sometimes males develop hair on their face, giving them a moustache. Males also have fatty tissues on their face creating cheek flaps, which show their dominance. The males also make loud noises with throat pouches. Females grow to about 4 ft. 2 in and weigh around 100 lb., while adult males can reach 5 ft. 9 in and weigh over 260 lbs. with an armspan of about 6’6.

Gibbons do not display much of sexual dimorphism. Some males have dark patches on their fur to show that they are suitable for mating.

http://www.bbc.co.uk/nature/life/Toque_macaque

In the case of old world monkeys, males can be up to double the size of females.

There are four different types of new world monkeys and they all display different characteristics. The first type is cebinae monkeys (squirrel and capuchin monkeys). Male squirrel monkeys weigh between 750 and 1100 grams while females weigh from 500-750 grams. In capuchin monkeys, males tend to have a larger head and body proportions than females. Aotinae (night and titi monkeys) tend not to have any sexual dimorphism. Atelinate (howler and spider monkeys) are sexually dimorphic by size and they also have sexually dimorphic canines. In the case of pithecinae monkeys, females have shorter hair then males. Their hair color is different as well. Females have brownish-grey fur and white or pale brown stripes on their face whereas males, have blacker fur, with a reddish-white forehead, face, and neck.

Male and female tarsier monkeys are sexually dimorphic in size. Males usually weight close to 120-155 grams and females weigh about 110-130 grams.

In the case of lorises, males and females you can see bimaturism. They grow at the same rate but at different times, the same time at different rates or at mixed rates at different times.

Finally lemurs display sexual dimorphism only in color. Most male lemurs are one solid color and females have a white patch on their backs.

So as you can see, we are not the only primates who display sexual dimorphism. Primates are also not the only species whom display sexual dimorphism.

For more information on the topic check out these sites and sources:

http://anthro.palomar.edu/primate/prim_1.htm

Click to access Biology_of_Nonhuman_Primates2(PDF).pdf