Lemurs (Prosimians/Strepsirhini) -  Lemurs are native to Madagascar and the Comoro Islands. Madagascar has a harsh seasonal climate that the Lemurs have had to adapt to. Specific things that the Lemurs do, help them to live under these harsh conditions. They occasionally store fat, hibernate when food sources are low, and have strict mating seasons. Most Lemurs live all of their life in the trees. Many of the larger species of Lemurs do live on the ground. Lemurs are usually active during the day and are very social. They live in family groups and the females have dominace over the males. Lemurs are forest creatures and many species live in Madagascar’s tropical rainforests, but some live in the dry deciduous forests. The lemurs’ muscular legs are adapted for jumping and their strong hans and fingers help them to climb trees easily. Lemurs are usually very small but they do vary in size depending on the species that you are looking at.

 The pygmy mouse Lemur is the smallest species 

of Lemurs. The pygmy mouse Lemur is actually 

the world's smallest primate. Their body length 

is usually only about 2.4 inches long with a tail 

length of up to 5.4 inches and only weigh about 

1.1 ounces. Lemurs can range anywhere from 1.1

 ounces to around 20lbs. The tails of all lemurs

 are usually longer than their body.

Most species of lemurs do exhibit 

sexual dimorphism, or different 

coloring between males and females. 

Both male and female ring-tailed 
lemur's have a fluffy, black-and-white 
striped tail. The only Lemur that 
is completely black is the male black 
lemur. The females have a white ruff 
around their black face and a white 
chest. The rest of the female's body 
is reddish brown. Both the male and 
female mongoose lemurs are a 
gray-brown color but the females 
have white cheeks and neck and the
males have red cheeks. 


Lemurs have fairly no competition with any other species of primates in Madagascar. They do, however, have competition amongst themselves. When Lemurs mate, they either have multiple male partners throughout one night, or the female chooses to have one male partner. In a study done, the larger lemurs had multiple partners while smaller lemurs decided to have only one. There is no precise answer to if the size of Lemurs has anything to do with their mating process or not. I believe the size of a Lemur does help them to move around the trees much quicker and faster. Also having a smaller body means that they require less food and nutrient. This makes it easier for them to survive in the conditions in Madagascar. 

Spider Monkey (New World Monkey/Platyrrhini) - Spider monkeys are new world primates that, most species, live in the tropical rain forests of Central and South America and live as far north as Mexico. Spider monkeys have long, lanky arms that help them to move from branch to branch in the rain forests. They also have gripping tails to aid in this. The spider monkeys spend most of their time up in the trees. They live in the upper layers of the rainforest's and forage. Due to their size, they require large tracts of moist evergreen forests. Black-headed Spider Monkeys are the largest spider monkey. They are an average weight of 24 lbs for males and 21.3lbs for females. 

Spider monkeys are not characterized by sexual dimorphism. The males and females are all about the same size and colors. There are a few differences between younger spider monkeys and their elders but not between the males and females. Not having a larger body or different colored hair or fur is completely fine for the spider monkeys since they do not have to worry about competition between each other. 

Baboon (Old World Monkey/Cercopithecidae) - There are five different species of Baboon's, all of which live in Arabia and Africa Baboons usually prefer savanna and other habitats that are semi-arid. A few baboons live in tropical forests. Baboons are ground dwelling animals and are found in open savannah, open woodland and hills across Africa. They do not have grabbing tails but do climb trees to eat, sleep and look out for danger below. In all species of Baboons, there is pronounced sexual dimorphism. It usually shows in the size of the Baboons when males are compared to females. Usually the males are larger. Specifically, the Hamadryas Baboon males are double the size of the females. The males fur is a silver-white color and the females are brown in color. The males also develop a large white mane and the females are mane less. 


Male Baboon's body measure up to 3ft and weigh between 40-70lbs and the female's body measures up to 2 ft and weigh between 20-35lbs. The tails of the baboons add about 1.3-2ft of extra length to the baboons.




The size of the male baboons compared to the females makes the males the stronger of the two. The males use their size to protect their females and themselves.




Gibbon (Lesser ape/Hylobatidae) - Gibbon's are a very small and lightweight animal.They spend most of their lives in trees. They are very acrobatic and fast primates. Gibbons are distributed in wild in the tropical and subtropical rain forests of Southeast, South and East Asia. They are also currently found in small populations in China, Laos, Vietnam, Cambodia, Thailand, Bangledesh, Northeast India, Myanmar, Malayysia and Indonesia. 


Gibbons are not sexually dimorphic in size. The males and females are about the same size. In some species, the Gibbons do have different colors from male to female. Since Gibbon's are generally small primates, they are also referred to as the "lesser apes". Most adult gibbons are only around 3 feet tall standing upright. They average around 12-22lbs in weight. The only Gibbons that show sexual dimorphism in size are the Siamangs. Since Gibbons are so agile and live amongst the tops of the trees, they do not need to be large to protect themselves, they are fast instead.

White-cheeked gibbons do have different fur colors. The males have black fur and skin with white fur on their cheeks. The females are golden or a reddish buff-colored and have black faces and dark brown or black fur on top of their heads. They also have white fur in a halo shape around their faces. 

Chimpanzee (Great ape/Hominidae) - Chimpanzees live in social communities with several dozen different animals. They can habituate themselves to African rain forests, woodlands and grasslands. Chimpanzees are found across a central band of the continent of Africa. Generally, chimpanzees are rain forest creatures. They span out around 21 different African countries from the west coast of the continent east through the vast central-African nation of Congo to the western reaches of Uganda, Rwanda, Burundi and Tanzani. Chimpanzees eat and sleep up in trees but they do spend most of their time on the ground. As long as Chimpanzees have access to forests that they can take shelter in and search for food, they can live in drier areas that have less trees. Male chimpanzees are larger than female chimpanzees. The average male chimpanzee weighs around 140-160lbs and the females weigh up to 110lbs. They are about the same height when standing upright. They live in a male dominated social structure. The males definitely have less tolerance towards other unfamiliar male chimpanzees, where-as the females don't.  

Each different type of primate definitely had a direct effect on their sizes from their living conditions. They use their body size to protect themselves either against each other or other species. The sexual dimorphism that is apparent in the different animals, seems to be more prominent in the larger animals. The smaller the animal, the less sexual dimorphism seems to be there. I also think that the smaller animals are safer amongst the high tree tops and do not need to protect themselves from anyone else. They have less competition so they haven't had to evolve as much when referring to their body sizes.  

Sources :

http://www.lemurworld.com/lemur-anatomy.html

http://animals.nationalgeographic.com/animals/mammals/baboon/

http://nationalzoo.si.edu/Animals/Primates/Facts/FactSheets/Gibbons/default.cfm

http://www.enchantedlearning.com/subjects/apes/chimp/